MXPA00003395A - Eye tracking device for laser eye surgery using corneal margin detection - Google Patents

Abstract

Systems, methods, and apparatus are provided for deriving the relative position of an eye (2) by tracking a boundary of the eye such as the limbus (10) (i.e., the interface between the white sclera (8), and the colored iris (6)), a technique for tracking the position of the eye (2) between the sclera (8) and the iris (6), and receiving reflected light from that region. The intensity of the reflected light is then measured to determine a relative position of the eye (2). In some embodiments, the measured region is scanned around the boundary. In other embodiments, a light spot is scanned around a substantially annular trajectory (200) radially outward from the pupil (4). The signals corresponding to the intensity of the reflected light are then processed, and measured to determine the eye's position. A flap of tissue (210) covering the boundary may be automatically detected so as to selectively measure the boundary away from the flap (210). The invention also provides for integrating the eye tracker (20) into a laser eye surgery system (16).

Description

DEVICE THAT TRACES THE EYE, FOR LASER SURGERY OF THE SAME, WHO USES THE DETECTION OF THE CORNEAL EDGE BACKGROUND OF THE INVENTION The present invention relates, generally, to ophthalmic surgery and, more particularly, relates to systems methods and apparatus for tracking the position of a human eye. This invention is particularly useful for tracking the position of the eye during surgical procedures, such as photorefractive keratectomy.

(PRK), phototherapeutic keratectomy (PTK), laser keratomielusis in if you (LASIK) or similar. In an exemplary embodiment, the present invention is incorporated into a laser ablation system, which "is capable of modifying the spatial and temporal distribution of the laser energy directed to the cornea, based on the position of the eye during this laser ablation procedure. In ophthalmic surgery, the ability to optically track or track the movement of the patient's tissue is recognized as the highly desirable element in laser delivery systems, designed to perform precision surgery on delicate ocular tissue. The eye includes not only voluntary movements, which can be inhibited with specialized treatment, but also involuntary movements that are more difficult to control in a living patient.According to the Eye Physiology described by Adler, even when the patient is held in a fixed "steady" on a visual objective, eye movement still occurs. involuntary movement of the head can occur, which causes further movement of the eye. Such movement can compromise the effectiveness of certain ocular surgical procedures that require great precision. This movement can occur even when the total immobilization of the eye is attempted. The total immobilization of the eye is not completely unfeasible in suppressing the involuntary movement of the eye, it is rather uncomfortable for the patient and can cause elevations in intraocular pressure that potentially threaten the eye. The realization of automatic eye tracking would alleviate any need for such immobilization and would offer a technique to more effectively accommodate all types of eye movements. Thus, the increasing surgery with a real-time eye tracking system can be improved in the accuracy and speed with which surgical procedures can be executed, as well as making possible new procedures, which will be carried out for the first time. Several techniques have been described to track eye movements. The following references describe techniques for tracking eye movements and are incorporated herein by reference in their entirety: Rashbass, Journal of the Optical Society of America, Vol. 50, pages 642-644, 1960; Crane and Steele, Applied Optics, Vol. 24, page 527, 1985; U.S. Patent No. 3,804,496 to Crane et al .; U.S. Patent No. 4,443,075 to Crane; U.S. Patent No. 5,231,674 to Cleveland et al .; U.S. Patent No. 5,471,542 to Ragland; U.S. Patent No. 5,604,818 to Saitou et al .; U.S. Patent No. 5,632,742 to Frey; U.S. Patent No. 5,752,950 to Frey; PCT International Publication Number WO 94/18883 by A ^ j ^ jga Knopp et al .; and PCT International Publication Number WO 95/27453 by Hohla. Many of the known tracking techniques fall into one of two distinct categories, optical point trackers and digital image trackers, the latter including numerous variations of pattern recognition and edge detection methods. Optical spot scanners use images reflected from several layers of the eye. These trackers optically distinguish the reflected light to form images such as a first, second, third and fourth images of Pur inje. For example, a double Purkinje imaging technique compares the displacement of two Purkinje images of different order in time and uses a repositioning device to adjust the isometric transformation that corresponds to the movement. A similar application of the double Purkinje technique, to stabilize a visual system, is used in the backlight and surveillance device. These image-based tracking methods, similar to that of Purkinje, are proposed to follow the J ^^ jj movement of the anterior surface of the eye. While such techniques possess, in principle, a sufficient velocity to follow the displacement of the Purkinje points, they include an implicit assumption that the eye moves like a rigid body. However, during surgery, the eye does not move like a rigid body. Thus, the location of Purkinje points can be influenced by transient relative movements between the various optical elements of the eye, which lead to the fictitious position information to identify the surface of the cornea. Furthermore, such systems are rather complex and tend to exhibit great variability among people in their calibration setting, which requires continuous real-time adjustments of the amplitude of the control signals. Also, during eye surgery, the optical quality of the eye is temporarily degraded. This temporary degradation of the optical quality distorts and makes the Purkinje images blurry. Therefore, these blurred images make the exact determination of the position of the eye very difficult.

Another class of tracking methods involve, in one form or another, digital image processing techniques. These techniques include retinal image tracker, various pattern recognition algorithms and edge detection techniques. In these cases, CCD cameras with very fast frame rates, sophisticated process algorithms and high-speed computer processes are required along with servo-controlled mirrors, to close the cycle. These requirements are usually caused by large amounts of digital data produced by the images used for the imaging process and the computation requirements to process images. With the frequency response limited in practice to approximately one tenth, the refresh rate, comparisons of digital images are considered to be relatively slow. In the case of tracing eye movements, the adjustment of the sampling frequency to an order of magnitude greater than the highest frequency to be pursued, is transferred in kHz regimes, * á? * ~ *? ..., leaving less than one thousandth of a second to process the signal information. Several other practical difficulties are found in most image processing techniques, which include the need for rather prominent and recognizable features, which are often easily located in the structures of the eye during surgery. Similarly, techniques based on the processes of high-speed video signal signals are often deficient due to the unfavorable exchange between the field of view, spatial resolution and frequency response. Specifically, since the image processing algorithms are limited by the size and spacing of the viewing elements (pixels), the digital methods are provided with a continuous resolution. . The increase in resolution accuracy is penalized in terms of the field of view. Still, relatively large areas must be acquired. One approach is to increase the number of pixel elements in an image sensor. Unfortunately, the increase in pixel resolution significantly increases MMiM ^ a ^ the cost of the system and degrades the frequency response of the system due to the increase of image data and computations. Alternatively, the fast moving optical deflectors and the associated control circuit systems can be employed. Unfortunately, this additional instrumentation also increases the cost of the system and degrades the response time of the system. Consequently, the system will have an unwanted combination of decreased resolution, decreased response time or increased cost. A more promising technique for tracking eye movement takes advantage of differences in the scattering properties of iris and sclera light. In that technique, light is projected onto the cornea / sclera interface, or limbus, and the scattered light from the limbus is detected by photodetectors, to determine an edge or boundary of a portion of the sclera and cornea. With this technique, the iris below the cornea will absorb the light that passes through the cornea and make the cornea adjacent to the sclera appear UU | ¡¡¡M dark. The relative position of this limit can then be monitored to track the position of the eye. Prior art techniques for tracking a boundary, such as limb, lack the desired combination of accuracy, speed and supply capacity, which would be desirable for use with laser eye surgery. A technique of tracking the limit of the cornea and sclera has been to project a simple area over a portion of the limbus and vary the position of the area along a line, so that the light reflected on a detector remains constant. The position of the projected zone is then assumed to represent the position of the limb. Unfortunately, measurements taken from a portion of an object, such as a single zone projected in the limbus, do not exactly represent the position of the entire object. One more disadvantage of tracking a single area is that the portion of the limbus being scanned can not be clearly visible or can change during surgery. One more technique for. tracing the limb has been to use detectors that detect the position and move a - '-' * - ~ - *** - »- ** > »> - * mirror to direct the element to a new displaced position of the eye. This additional electronics typically involved with these techniques can increase the cost of the system and can increase the cost of the system and decrease the response time of the system. Several factors also limit the effectiveness of this approach, particularly its sensitivity to individual variability between the eyes, such as variations in iris diameter and variable contrast between the iris and the sclera. In addition, systems that use this approach will typically only sample a limited portion of the limbus, and that portion of the sampling limit may be covered by tissue during surgery. Another problem that exists with eye tracking systems, which measure the position of the limbus, occurs when this limbus is covered by tissue during surgery. An example of a surgical procedure that covers a portion of the limbus is keratomielusis in your laser (LASIK). During this procedure, the epithelium, Bowman's membrane, and a portion of the anterior stroma are They are partially cut from the stroma and bent back to expose the stroma to the laser. Partially removed corneal tissue is typically folded back away from the center of the cornea and placed over a portion of the limbus. The cut tissue that covers the limbus, however, is extremely rough and with poor optical • surface. Therefore, systems that depend on the reflection or scattering of light from this region of the eye, do not provide significant data. Also, the position of the fin may vary among surgeons. This variability of the position of the fin can cause further problems with the eye trackers of the prior art. For example, a surgeon may not be able to perform LASIK as desired, because his preferred orientation of the fin of the cut tissue may cover a portion of the eye used by the eye tracker. Laser surgery systems that have been integrated with eye trackers in the past, used in the eye tracker, provide a central reference. »< & > - .. riitaMiMlHMMIMMMITFltfi • MMMÍÉÉ ^ AI The performance of these integrated systems of surgical laser and eye tracking is often less than optimal, when used with the LASIK surgical procedure. With this LASIK surgical procedure, the central features of the cornea and underlying tissues are not easily located due to the rough corneal surface produced by the incision. In addition, laser treatment can change the corneal tissue and make tracking more difficult by changing the visibility of a characteristic tracked. Another limitation of the eye trackers, according to the prior art, has been the algorithms used to couple the displacement of the laser beam to coincide with the movement of the eye. For example, some systems repeatedly adjust a beam directed toward an intended target, until the two positions are aligned. This repeated adjustment of the laser beam will retard the laser treatment. These delays of the laser treatment are not convenient, because they can cause the drying of the eye and remove too much tissue from the dried eye.

^ **** **. , ".. - ... J ^ .. ^^.", AiUt Therefore, what is needed are improved methods and apparatus to track the eye. In particular, these methods and apparatuses must be able to accurately track the movements of the eye in real time, so that these movements can be compensated during, for example, a laser ablation procedure. It would be particularly convenient if these methods and apparatuses could be used during procedures in which a portion of the external reflecting surface of the eye (i.e., the epithelium, and / or the anterior corneal tissue) is variably removed, such as in the LASIK procedures. . Furthermore, it would be desirable if these eye tracking techniques were optimally integrated with a surgical laser system.

COMPENDIUM OF THE INVENTION The present invention is directed to systems, methods and apparatus for tracking the relative position of the o o. This invention is further directed to systems, methods and apparatuses for notching an eye to a predetermined configuration, by photo-ablation, while tracking the relative position thereof. In particular, the techniques of the present invention derive "the position of the eye by tracking the interface between the white cornea and the colored iris (i.e., the limbus.) This limbus, located at the outer edge of the cornea, has several advantages such as a tracing area mark for corneal procedures, for example, the limbus is contiguous with the target corneal tissue and is expected to provide an accurate representation of the non-surgically induced displacements, yet it is located far enough away from the site of operations, so that the transient displacements caused by the impact of the laser pulse at the target site will be sufficiently reduced to avoid inducing dummy tracking signals, in contrast to the processes based on the process of images or the optical point trackers, the systems and methods of the present invention involve the tracking of contrast that does not depend on the edges and / or patterns well In one aspect of this invention, a method for tracking the movement of the patient's eye comprises directing light to an annular region of the eye, between the sclera and the iris and receiving the light reflected from that region. The intensity of the reflected light is then measured to determine a relative position of the eye. In some embodiments, an annular light pattern is directed over a region of the eye radially "outward from the pupil." In other embodiments, a zone of light is swept around a substantially annular path, radially outward from the pupil. which correspond to the intensity of the reflected light are then processed and measured to determine the position of the eye relative to the annular pattern or trajectory.Preferably, the annular light pattern or trajectory will be sufficiently broad to include both the sclera and the sclera. iris (that is, wider than the transition region of the limbus) Since the light reflected from the sclera has a greater intensity than the light reflected from the iris, the total surface area of the sclera and the iris within the a - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -. In a specific configuration, a zone of light is swept around an annular path, which substantially coincides with the limbus, between the sclera and the iris (which may have different configurations for different patients). The path of the light is adjusted so that it is substantially concentric with the limbus at the start of the procedure. An alternative component of current of the same frequency as the frequency of the light zone, it is generated as a reference signal. The amplitude of the signal of the light zone can be compared with the amplitude of the reference component, to determine the magnitude of the displacement of the eye, and a phase of the signal of the light zone can be compared with a phase of the light component. reference, to determine the angle of the displacement vector of the eye. For example, if the eye is rotated laterally with respect to the annular path, the reflected light from one side of the annular path will have a greater intensity because - ^^^^^^^^ The sclerotic would occupy most or all of the annular path in this region. The intensity of the other side of the trajectory will be much smaller, because the iris would occupy most, if not all, of this region of the trajectory. Thus, the amplitude of the frequency signal will increase above the reference intensity signal as the light is swept on the side of the eye containing mainly the sclera. The frequency signal will then decrease below the intensity signal reference as the light beam travels to the other side of the limbus that contains mainly the iris. The resulting sinusoidal signal can be compared to the reference signal to determine both the magnitude and displacement of the eye vector. 15 Light can be swept around the annular path using a variety of different techniques. In one embodiment, the light is transmitted from a light source through one or more optical fibers to the eye. These optical fibers include a section of proximal transmission coupled to the light source and a distal section of transmission / reception, placed in front of the eye. The distal region can be rotated about a substantially annular path, so that light will sweep around the eye along this path. Similarly, the light is then received by the distal region and passes through it to the second proximal fiber section (which may be the same or different from the set of fibers as the transmission fibers). The light is received by a light detector, such as a phototransistor, a CCD, or the like, and the corresponding signals are processed to generate an analog oscillation signal representing the position of the eye. In another embodiment, the light steering system includes a light source ring placed around the eye in a line with the annular track. The light sources are activated in sequence to "sweep" the light around this annular scan. Alternatively, the light sources can be activated simultaneously, so that the annular pattern of light is directed onto the eye. The annular pattern of light can be measured as a total to determine the position of the eye, or each light source can have a corresponding photodetector that measures the intensity of the individual light beams. In another embodiment, the light steering system includes one or more oscillation mirrors, for example galvanometer mirrors, placed between a light source and the eye, to sweep light around the limbus. In another aspect of the invention, the systems and methods are provided to track the relative position of the eye during a surgical procedure, such as photorefractive keratectomy (PRK), phototherapeutic keratectomy (PTK), keratomileusis in if your laser (LASIK) or the like . During the laser ablation procedure for PRK, the epithelium is removed to expose the underlying Bowman layer of the cornea. In LASIK procedures, the epithelium, Bowman's membrane and a portion of the anterior stroma are partially cut from the stroma and bent back to expose the stroma to the laser. An ultraviolet or infrared laser is used to remove a microscopic layer of the anterior stromal tissue from the cornea, to alter its refractive power. In accordance with the present invention, the relative position of the limbus is traced, as described above, and the laser beam is modulated to compensate for eye movement. The present invention is particularly useful during LASIK procedures, because the light path passes above and below the region of the tissue, which has been bent or removed from the eye. The light that passes through the portion that has been cut will generally provide little information regarding the position of the limbus. However, since the path of the light is of a known configuration (ie, a circle, oval, etc.) the entire trajectory can be interpolated from the information obtained from the regions superior and inferior. In yet another embodiment of the invention, this invention provides a method for tracking a position of an eye that has a limit, such as the limbus. The method includes directing an energy of "light in the eye and measuring the intensity of the reflected energy of a region of the eye.

This region includes a portion of the limit. By sweeping the measured region around the eye, the position of the eye is determined by a variation in the intensity of the reflected energy. In some embodiments, the size of a dimension across the measured region is restricted by selectively passing light rays from within the region to a detector of light energy, and excluding light rays from outside the region of the region. light energy detector. By rotating the measured region around the eye at a reference frequency, a variable signal is generated at the reference frequency. By comparing an amplitude of the variable signal with a reference, a magnitude of a displacement of the eye can be determined. By comparing a phase angle of the variable signal with the reference, an angle of the eye position can be determined. The method can also include the path placement to be substantially coincident with the limit, and adjust a radius of the path to coincide with a radius of the limbus. rfMS ^^^ AteMß.-i á? ^ i-ÉÉritt In a further embodiment of the invention, this invention provides a method for tracking a position of an oo, which has a limit by projecting a beam of light energy into the eye and measure the intensity of the energy reflected from a region of the eye. This region includes a portion of the boundary and is aligned with the beam. By sweeping the beam and the region around the eye, the position of the eye is determined by a variation in the intensity of the reflected energy. Optionally, the size of a dimension across the measured region can be restricted by selectively passing light rays from within the region to a detector of light energy and excluding light rays from outside the detector region of light energy. By rotating the measured region around the eye at a reference frequency, it can optionally generate a variation signal at the reference frequency. In yet another embodiment of the invention, this invention provides a method for tracking a position of an eye, which includes projecting a beam of light from a display element over the eye and measure the intensity of the energy reflected from a region of the eye. The region includes a portion of the limit.- Sweeping the beam around the eye, the position of the eye is determined from a variation in the intensity of the reflected energy. In still another aspect, the invention provides a method for tracking a position of an eye during surgery. The eye has a limbus, and the method involves directing light energy into the eye. An intensity of the energy reflected from a region of the eye is measured, this region includes a portion of the limbus. A fin of the cut tissue covering the limbus is automatically detected. In yet another embodiment of the invention, this invention provides a method for treating an eye with a laser treatment energy beam, which comprises automatically detecting a fin cut from the tissue covering the limbus of the eye. This method also includes directing a light energy in the eye, measuring the intensity of light energy reflected from a region of the eye and applying the treatment energy to the structure of the tissue over the eye. In yet another treatment of the invention, this invention includes an eye tracker for measuring a position of an eye that has a boundary, and this tracker includes a controller coupled to a light detector for the automatic detection of a tissue that is udder. this limit. The controller measures the energy of light reflected from an uncovered portion of the boundary to determine a relative position of the eye. The modality also includes a light source to obtain light energy, a light detector positioned to receive the light energy reflected from a region of the eye, and an optical train to sweep the region over the eye. The modality can also include a reference circuit, for a zone of visible light projected on the detected tissue, which covers the limit, an interpolation circuit, to interpolate the energy of the measured light, and a displacement circuit to displace the trajectory annular to correspond with the position of o o.

In still another embodiment of the invention, this invention includes a laser surgery system integrated with an eye tracker. The system includes a laser for the generation of a beam of an ablative laser energy, and a moving laser beam path is variablely moved from a reference position. The eye tracker includes a mobile eye tracker shaft. This axis of the eye tracker can be moved so that the position of the eye tracker axis coincides with a position of the eye. This axis of the eye tracker can be moved independently in relation to the path of the mobile laser beam, according to a position of the tracer axis of the o o and the value of a laser treatment table. In light of the above, it is an object of the invention to measure, rapidly and accurately, the position of an eye, by measuring an eye limit.

Mrf * SajMan «B, > ... ^ AlM ^ ÉIIliklM J ^^ J ^ ^ stójj ^^ jg gj jg ^ l & BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a front view of the superficial anatomy of the eye, illustrating the contrast between the iris 5 and the sclera. Figure 1A is a schematic view of a laser surgery system to incorporate the invention. Figure 2 is a block diagram of the basic components of the optical system and the method of the present invention. Figure 3 is a functional block diagram of an optical system for tracing the boundary between the iris and the sclera, according to one embodiment of the present invention. Figure 4 is a block diagram of a control circuit for determining the polar coordinates of magnitude / phase of the center of the eye based on the signals received from the optical system of Figure 3. Figure 5 is a schematic view of a zone 20 of light swept around the iris / sclera border, which illustrates the case in which the optical axis of the eye is aligned with the optical system. Figure 6 is a graph illustrating the signals received by the control circuit of Figure 4 in the case of Figure 5. Figure 7 is a schematic view of a zone of light swept around the iris / sclera boundary, which illustrates the case in which the optical axis of the eye is not aligned with the optical system. Figure 8 is a graph illustrating the signals received by the control circuit of Figure 4, in the case of Figure 7. Figures 9 and 9A are schematic views of the area of light swept around the boundary of the iris. / Sclera during a LASIK procedure. Figure 10 is a schematic view of a ring of light sources, for incorporation into an embodiment of the invention, Figure 11 schematically illustrates the use of a rotary opening in a embodiment of the invention.

Figure 12 illustrates schematically one embodiment of the invention, which uses a projected zone aligned with a barrier opening a region measured around the limbus. Figure 13 illustrates schematically one embodiment of the invention that includes a cathode ray tube screen, for projecting a zone of visible light onto the eye. Figure 14 schematically illustrates a The method of the invention includes directing the model of the area of light projected onto the covered region of the limbus and displacing the trajectory of the area of the swept light to correspond with the position of the eye. Figure 15 is a block diagram schematically illustrating a control circuit that provides the displacement and model of the swept light zone as in Figure 14. Figure 15A is a block diagram, illustrating an illustrated reference circuit to Figure 15.

Figure 15B is a block diagram illustrating an automatic fin detection circuit, referred to in Figure 15. Figure 15C is a block diagram illustrating a user interface circuit referred to in Figure 15. Figure 15D it's a block diagram, which illustrates an interpolation circuit referred to Figure 15. Figure 15E is a block diagram, illustrating a time circuit referred to Figure 15. Figure 15F is a block diagram, illustrating a displacement circuit. Referring to Figure 15. Figure 15G is a block diagram, illustrating an error detection circuit, referred to in Figure 15. Figure 15H is a "block diagram, illustrating a light detector circuit, referred to in FIG. to Figure 20 15.

Figure 151 is a block diagram, illustrating a feedback circuit, referred to Figure 15. Figure 15J is a block diagram, which illustrates a CRT circuit, referred to Figure 15. Figure 15K is a diagram of blocks, which illustrates a circle generating circuit, referred to in Figure 15. Figure 15L is a block diagram, which illustrates a computer interface circuit, referred to in Figure 15. Figure 16 is a schematic illustration of overlapping a pulsed light scanning or scanning zone, which occurs while the light zone scans around a limit, in one embodiment of the invention. Figure 17 is a schematic illustration of overlap of pulsed sweep light areas, in which the path of the zones is shifted to coincide with the displacement of an axis. ^ ** ^ **** yy? ± - £ ~~. " ... ^^^ i ^^^ ^ i ^. ^ * - .miajfft iJTTi - Figure 18 is a schematic illustration of one embodiment of the invention, including an eye tracker, integrated with a laser surgery system . Figure 18A is a block diagram, illustrating a laser system controller of the invention, used to control the laser system of Figure 18. Figure 18B is a block diagram illustrating a computer routine of the invention, for use with the laser system controller of Figure 18A. Figure 19 is a schematic illustration of one embodiment of the invention, which uses the same beam deflection module to deflect both a scanning laser treatment beam and a light beam to measure the position of an eye. Figures 20 and 21 are schematic illustrations 15 of the method of ablation of a mobile eye, with a laser beam.

DESCRIPTION OF THE PREFERRED MODALITY The present invention is directed to systems, methods and apparatus for tracking the relative position of the eye In particular, the techniques of the present invention they detect the contrast in limits at a recognizable large scale, such as the cornea / sclera interface (limbus), to determine the location and orientation of these boundaries, often without resorting to image processing techniques. Although limbus is the preferred limit, one skilled in the art will recognize that other limits (such as the edge of the pupil / iris interface) can be tracked with the techniques of this invention. In preferred aspects, the cornea / sclera interface is tracked with a light zone, which is swept around an annular path, to supply an oscillating signal indicating the magnitude and displacement of the limbus from a reference position. For corneal procedures, which include refractive surgery, the limbus of the or or on the radially outward edge of the cornea provides sufficient contrast to allow the use of the screening methods discussed in this invention. In addition, the limb has the advantage of not only moving with the cornea - - as it is a part of the cornea - but, since it is connects similarly to the sclera, will not respond so drastically to the transient deformations associated with refractive surgery. The invention often includes directing. light energy to the eye. This light energy will be directed towards the eye as a beam of energy. The intersection of the beam of light energy with the eye will comprise a zone of light formed in the eye. Various techniques can be used to define a measured region that can be scanned or swept over the eye. In one embodiment, a projected zone of light energy can be used to define the measured region. This measured region can be swept over the eye, sweeping the projected area. In another embodiment, an opening defines a measured region by restricting an area on the surface of the eye, which can reflect the light energy from the measured region to a light energy detector. In other modalities, the measured region is defined by projecting a zone of light over a restricted area of the eye, and the restricted area is further defined by selecting the rays of the eye. light from the restricted area and_ excluding light rays from outside the restricted area. While exemplary embodiments of the present invention will be described herein with reference to systems having a signal processing circuit system, digital data processors and, in particular, combinations of analog and digital components, it must be recognized that the present invention encompasses / and provides advantages for) tracking systems and methods which are more digital (or even exclusively digital) in nature. As digital processors become increasingly capable (particularly for the imaging process), faster and less costly, and like the optical components of the digital electronic interface (eg, CCD sensors, flat panels and other lighting arrangements) selective, image captures and analysis systems, and the like) improve in the response time and in resolution, some or all of the analog components can, now or in the future, be replaced with the hardware (computer equipment), software ( Program) . ^ ys digital or a combination of hardware and software. Similarly, more predominant analog systems can also be made, or even systems that make use of optical signal manipulations. Therefore, those skilled in the art of digital signal processing will understand that digital computer process systems can augment or replace the structures and functions illustrated and described herein with reference to the analog components. Referring to Figure 1, the surface anatomy of a human eye 2 is illustrated. As shown, eye 2 includes a pupil 4 in the center, surrounded by a dark region 6 of the iris. The iris 6 is surrounded by the white sclera 8, covered with a transparent mucous membrane or conjunctiva. Transparent cornea 12, through which light enters the eye, warps anteriorly from its joint with sclera 8 (see Figure 2). The iris 6 is the visible color part of the eye, which is placed between the cornea 12 and the lens 14 and its round central opening, the pupil 4, allows light to enter the eye.

Although irises can be many colors, they usually reflect light at a particular intensity. The sclera 8 is the white portion of the eye, which generally reflects light at a greater intensity than the iris 6. 5 The region that interfaces with the cornea and the sclera is typically referred to as limbus 10. This region is a region substantially annular, which provides a high contrast between the sclera 8 and the cornea 12. This high contrast can generally be attributed to the cornea 12 underlying the iris 6, which absorbs the light that passes through this cornea 12. Referring to Figure 1, this figure schematically illustrates a surgical laser system 16. This laser surgical system 16 includes a laser 17 for generate a beam 18 of laser energy. The eye 2 is placed under the laser surgery system 16 for treatment with a beam 18 of laser energy. The eye 2 is conveniently aligned with the laser surgery system 16, before the treatment of the eye with this laser beam.

¡^ ^ M¿ &¡¡¡¡Referring to Figure 2, an optical system 20 for projecting light onto the limbus 10, to measure the light reflected from the region to track eye movement is illustrated schematically in accordance 5 with the present invention. The optical system 20 generally includes a light source 22 for directing a single or a plurality of light rays 24 through an optical train 26 in the limbus 10 of the eye 2. This optical train 26 includes a light direction apparatus 28 to sweep or project in light ray sequence 24 around a path 29 that coincides with (at least initially) the limbus 10. Alternatively, the light source 22 and the optical train 26 can be configured to direct a pattern of light in the limbus 10. 24 light rays are scattered from the eye to through collection optics 30 (which may be part of the optical train), which again focuses the scattered light 32 on a light detector 34 to form the measurable signals. The system will preferably include filters (not shown) in the optical train 26 and / or collection optics 30 u ktiHfry | fj .. "^,., ...- •" 'jlfj? ^ jiiflhf to filter the spurious light These filters are generally transmitters to the radiation at the wavelength of the light source, while reflecting the radiation at other wavelengths This helps to separate the light guides 5 projected onto the limb of the eye from other light source in the operating space A computer 36 and a control circuit 38 are in electrical communication with the detector 34 for processing the corneal edge signals and measuring the relative magnitude of the displacement of the eye 10 Referring now to Figure 3, one embodiment of the present invention will be described in detail, as shown, an optical system 40 comprises a light source. 50, which is activated by a power supply (not shown) to pass light rays through a fiber Y-shaped optics, 54, to the eye. The light source 50 may comprise one or more light sources, for example, lasers, such as argon, helium-neon and diode lasers, or the like, halogen light sources, "light-emitting diodes, and the like. In one embodiment, the light source 50 will emit light that has a red wavelength up to about infrared, around 700 to 900 nanometers. This wavelength range has the highest sensitivity for many detectors and also allows the optics to filter light from other sources, such as a light seen in the microscope or the like, from the operating space (which is typically in the range from 400 to 700 nanometers). The source 50 of infrared light can be configured to directly emit such wavelengths, for example, light emitting diodes, or it can be equipped with one or more filters (not shown) that only transmit wavelengths within the range of red to near infrared. Alternatively or additionally, the system may include a source 52 of visible light, which emits a visible wavelength to produce a ring Visible light in the limbus that can be useful for other purposes (for example, the initial caliber of the path of light over the limbus). Since the systems and methods of the present invention avoid dazzling light directly through the iris opening, they are generally safe for the retina.

The fiber optic 54 includes a proximal transmission section 58, optically coupled to the light sources 50, 52, to transmit the light rays through a common trunk 56 to a distal section 60 of transmission / reception, which is suitably configured to transmit rays of light on the limbus 10 of the eye. The distal fiber transmission / reception section 60 is rotated in a circular fashion with its end constantly maintained on an annular path 70 through the use of a suitable mechanical bearing (not shown). The optical fiber 54 further includes a receiver section 62 coupled to the distal section 60 for guiding the scattered light to a phototransistor 64. This optical fiber 54 includes dedicated multiple fiber sections of transmission and reception, on a common trunk 56, with individual fibers which belong to the sections of the transmitter or receiver or which are randomly intermixed. The stem 56 of the composite fiber 54 can be as long as necessary and is quite flexible. The receptor fibers are positioned to capture scattered light from the eye and to guide this light to an end 72 of receiving fiber. The rays of the scattered light pass through the fiber end 72 and collide on the photosensitive surface of the phototransistor 64, which converts the light into electrical signals. A read amplifier 65 amplifies the signal 122 of the corneal edge and sends forward this signal 122 to an electrical system 120 (see Figure 4), as discussed below. A synchronous stepping motor (not shown) can be used as a pulse to rotate the end of the section 60 of distal fiber about path 70, although other suitable pulses may be used with the present invention. In addition, a second pulse can be used to initially calibrate the rotation path of the optical fiber, so that it is concentric with the limbus. of the eye (additional details of this method are discussed below). In one embodiment, this calibration pulse includes a motor pulse 80 of the radius, which has a high ratio mechanical reducer, such as an endless gear 82, and a mechanical coupling 86 for coupling an engine. 84 DC to the end of the optical fiber 60.

When the desired radius is achieved, the DC motor 84 can be removed and the endless gear 82 will keep the radius constant during the procedure. As shown in Figure 3, the optical system 20 may further include a reference signal system 90 that generates a reference synchronization signal 119 for comparison with the signals produced from the optical fiber 54. In one embodiment, the system 90 of reference signal includes a timing disk 92 having a hole 94 in its perimeter and a light source, such as a light-emitting diode (LED) 96, for bright light through the hole 94 in the rotating disk 92 to a phototransistor 98. As shown, the system 90 of the reference signal includes a synchronized LED impeller 100 and a synchronized phototransistor amplifier 102, coupled to the phototransistor 98. A rotary motor 104 having a stepping motor pulse 105, it is coupled to the synchronizer disk 92 to rotate it to a reference synchronization frequency.

Referring to Figure 4, an electrical system 120 is illustrated for receiving and processing the reference signals 119, 122 and the corneal edge from the optical system 20. It will be appreciated that this conversion of the light pattern to the electrical signals by the phototransistors 64, 98 effectively constitute the delivery from the optics to the electronic subsystem. As shown, a first input in the electrical system 120 is the signal 122 of the corneal edge, received from the phototransistor 64. In order to improve in relation to the signal to the noise, the signal 122 of the corneal edge is preferably filtered using a programmable bandpass filter 124, tuned to the rotation frequency. Alternatively, the impeller 50 of the infrared LED can be pulsed at a specific known frequency and the programmable bandpass filter tuned to the specific frequency of the LED driver. After the amplitude is stabilized and limited by an automatic gain control 129 and a limiter 128, respectively, the filtered signal 128 is applied as an input within the phase comparator 130. The second input to the phase comparator 130 is the reference synchronization signal 119, from the synchronous wheel 92 on the rotary motor shaft. The output of the phase comparator 130 is at a relative angle of the displacement 136 of the eye, which is digitized in an analog / digital converter (A / D) 134 for further processing. The filtered signal 129 of the corneal edge is used to measure the relative magnitude of the displacement of the eye dividing the peak amplitude of the alternating current (AC) component (at the rotation frequency) by the value of the direct current component (DC), using a divider 138. Specifically, the filtered signal 129 of the corneal edge and a gain are inputs on an amplifier 144 , filtered through a DC pass filter 146 and then enters the splitter 138. The output of the operational amplifier 144 is also input to a peak detector 150, from which the peak amplitude to the splitter 138 is output. of divider 138 is a signal 140 that represents the relative magnitude of the displacement of the eye, fij¿ H ^ ng ^ that is digitized by the 142 A / D converter for the further process. In order to maintain flexibility, all the gains and set points of the tracking system are preferably programmable by the digital converters in analog, under the control of the user. The "Captured Crest" signal 151 provided by the ridge detector 150 is sent to a flip flop 152, which indicates that the angle and magnitude data are ready to be transmitted to the user. A reference variable is a voltage programmed by the user, which achieves the desired radius of gyration when the user manually adjusts this radius using a visible light zone and sees the zone path through a wide-field microscope (not shown) . Specifically, a radius adjustment point 160 can be programmed by the user and enters the electrical system 120 by means of a D / A converter 162. The desired radius 164 of the light path can be adjusted, for example, by sweeping a area of visible light over the eye until the visible light path is substantially The matching radio with the limbus 10. The desired radius 164 is entered into the operational amplifier 166 with a gain 168, and the output of the operational amplifier 166 is applied to the motor 80's pulse of the radius. A position feedback system can be provided to maintain a constant of the radius after achieving a satisfactory locking at the corneal edge. In other modalities, the zone path can remain under the control of the digital process system, before, during and after locking. The protection and diagnostic circuits can also be provided for the supervision of the limits of the radius of rotation, minimum and maximum, and for poor functions of the rotary motor and the system of associated impulse circuits. For example, the user can enter the upper and lower limits 170, 172 in the path radius. A desired frequency 190 of the light path can also be input via the D / A converter 192 in a frequency generator 194. This frequency generator 194 is suitably coupled to a pulse 105 of ^^ Hgta | stepping motor for rotating the synchronous disk 92 to the desired frequency 190. As shown in Figure 4, the desired frequency 190 can be compared to the actual frequency of the reference signal in a frequency comparator 196. A "0" gate 198 is coupled to the flip flop 199 to adjust or readjust the optical system 40 if the path is too far in the sclera or iris (outputs from the upper and lower radius limits 170, 172) or if there is a error in the desired frequency from the comparator 196. The trace is initiated and stopped by the commands issued by a CPU (not shown). Since the CPU typically comprises a collector based on the digital VME, it is understood that the provisions are included for issuing the start / stop tracking commands in the digital format. Further, when the tracker of the present invention is part of a larger system, the CPU provides an essential link for the interface with other sets, such as an axial path or an objective vision system. As described above, structures of Tracking alternatives may rely on a greater extent in digital lighting, detection and signal processing components. Referring to Figure 5, a method for tracking a human eye during a surgical procedure will now be described. The present invention can be used in conjunction with a wide variety of surgical procedures in the eye, and is particularly useful with laser ablation procedures, such as photorefractive keratectomy (PRK), phototherapeutic keratectomy (PTK), keratomileusis in si tu laser (LASIK) or similar. In such procedures, a laser is prepared to deliver the appropriate radiation, according to the calculated beam delivery parameters, for the specific procedure, for example, the power level and the spatial location on the corneal surface. In the PRK or PTK procedures, the epithelium is completely removed to expose the anterior region of the stroma. In the LASIK procedures, the epithelium, Bowman's membrane and a portion of the anterior stroma. they are partially cut from the stroma and bent back to expose the stroma to the laser. The laser beam is typically controlled to collide in the cornea area of an eye to form there a predetermined ablation configuration. The laser selected for use, preferably emits on the ultraviolet side, ie at wavelengths less than substantially 400.0 nm. Further details of the suitable system and laser ablation procedure performance methods can be found in US Patents Nos. 4,665,913, 4,669,466, 4,732,148, 4,770,172, 4,773,414, 5,207,668, 5,108,388, 5,219,343, 5,683,379 and 5,163,934, the complete descriptions of which are incorporated herein by reference. here as a reference As shown in Figure 5, the system is initially calibrated by adjusting the radius of the zone path 200 using a zone 202 of visible light and sweeping the area of light around the eye 2. When the light zone 202 is swept around a path that substantially coincides with the limb 10 of the eye, the system locks this path to provide a reference path in which the relative position of the eye is to be measured. As shown in Figure 6, if the light path 200 is exactly coincident with the limbus 10 of the eye, a signal of substantially constant intensity must be produced with the electrical system 200. This is because the intensity of the scattered light of the eye does not change substantially as it passes along the trajectory (each point in the trajectory will generally have the same amount of sclera and the same amount of iris, which will produce a signal of generally constant intensity). Of course, it will be recognized that this intensity signal will not be exactly constant as the reflex capacity of the eye (which includes the limbus) varies spatially. In addition, it is difficult to align the light path, so it is exactly coincident with the limbus 10, and the width of the silt can vary around its perimeter. However, these variances can generally be taken into account when calibrating the system. With reference to Figures 7 and 8, when the patient moves the eye, the limbus 10 will no longer be aligned with the zone path 200. For example, Figure 7 illustrates this misalignment when the eye rotates laterally relative to the zone path 200. In position A, the light zone 202 is positioned so that it covers more of the white sclera 8 than the iris 6. Consequently, the intensity of the scattered light will increase above the reference intensity in position A, as shown in FIG. shown in Figure 8. In position B, the area of light is completely focused on the white sclera 8, which results in an intensity signal approaching maximum intensity. As the light moves down to position C, it is now almost completely covering iris 6, which will result in an intensity of light less than the 50% reference value. Similarly, in the D position, the light zone is completely focused on the iris 6, which results in the minimum intensity signal, as shown in Figure 8. The resulting signal will approximate a sinusoidal signal that contains the magnitude and phase of the displacement of the eye. This signal can be compared to the reference signal to determine both the phase and the magnitude of the eye displacement. If the eye is being tracked during a surgical procedure, this information can be transmitted to the processor to modify the ablation algorithm to take into account the different positions of the eye relative to the optical axis of the laser and the focusing optics. Thus, the laser beam can be modulated or modified in another way, so that the desired ablation pattern in the eye is not effected by its relative movement. Referring to Figure 9, a method for tracking the relative movement of the eye during a LASIK procedure will now be described. In LASIK procedures, Bowman's epithelium and membrane, and a portion of the anterior stroma, are partially cut from the stroma and folded back (or completely removed) to expose the stroma to the laser. As shown in Figure 9, this fin 210 is generally a rectangular piece of tissue extending from the sclera 8 and a side of the iris 6 through ^ Flß ^ ^ .MlMaU *. all iris 6 and pupil 4 to sclera 8 on the other side. Alternatively, the fin does not need to extend across the entire cornea, and the incision may be limited to a portion of the cornea, as illustrated in Figure 9A. Of course, it will be recognized that the fin 210 may have a variety of configurations besides the rectangular one. For example, the flap may be circular, as illustrated in Figure 9A. The appearance of an underlying region 212 has been altered by the incision to present a poorly defined boundary. Therefore, any light scattered from this region 212 will contain a negligible value for determining the position of the eye. As shown in Figure 9, the present invention has the distinct advantage that the rotation path 200 generally extends around the entire limbus 10 of the eye. The portions 220, 222 of the path 200, which extends below and above the removed fin 210 will not be relatively affected by the incision. Therefore, the information from these regions can be used to extrapolate the entire position of the limbus 10, which includes the portion that has been cut or covered now. Specifically, the zone path 200 is calibrated prior to the LASIK procedure, as discussed above. After the fin 210 has been cut, the light is swept around the calibrated, predetermined zone path 200. Light passing through the upper and lower portions, 220, 222 of path 200, will be processed as discussed above. Since the trajectory is of a known configuration (ie a circle, a oval, etc.), the entire path can be interpolated from the information obtained from the upper and lower regions, 220, 222. In an alternative embodiment, the light zone 202 can be swept around the path 200, using a ring of light sources, as shown in Figure 10. A ring of light sources 230 includes a plurality of light sources 232, 234, 2326, 238, 240, 242, 244 and 246, positioned so as to define a light source. ring arrangement 248. A light detector 249 is placed to detect reflected light from the eye 2. The ring 230 is placed so that a individual light source, such as 232, produces a projected area of light 202 in eye 2. Sequential activation of light sources 232 to 246 cause projected light zone 202 to sweep through path 200. the light reflected from the projected zone 202 is converted to the corneal edge signal 122 by the light detector 249. As illustrated in Figure 11, the measured region of the limbus can be swept using a source of uniform illumination and selective light detection. An optical train 249 'here includes a lens 252 which forms images and a rotating disk 260. A limbus 10 of the eye 2 is illuminated with a light source 250, which directs the light energy in the eye and thus supplies an almost illumination limbus uniform 10. A lens 252 forms an image 254 of the eye, near the surface of an optically non-transmitting material 259, here in the form of a rotating disk 260. Image 254 of eye 2 includes limbus 10. The trajectory 200 of the measured region 257 is positioned to be coincident with the limbus 10. The disc 260 includes an opening 256 formed in material 259, optically non-transmitting. This opening 256 is placed in front of a detector 258. The detector 258 generates an electrical signal to measure the intensity of the light energy reflected from the o o. A dimension through the measured region 257 of the oo 2 is restricted to the image portion 254 which passes selectively through the opening 256 formed in the rotating disk 260. This disk 260 excludes light rays outside the region. measure 257 to reach detector 258. Rotary disk 260 will cause aperture 256 to rotate around image 254 of limb 10, which is formed on disk 260. This rotation of aperture 256 around image 254 will cause the region measurement 257 of the eye 2 bar around a path 200. In some embodiments, the aperture 256 can be supported movably on a guide (not shown) that slides radially along the disc 260 to adjust the radius of the path 200 of the measured region 257. This adjustment is preferably made to coincide with the Fig. 1: A ^^ MBIMtoa .., radius of rotation of the opening 256 with the radius of the image 254 of the limbus 10 The rotary opening 256 around the image 254 of the limbus 10, produces a signal 122 of variable corneal edge from a light detector 258. The position of the eye is determined by a variation in the intensity of the reflected light energy. The rotation of the disk 250 can be synchronized with the measurement of the electrical signal 262 by rotating the synchronization flag 264 through a sensor to produce a reference signal 119. In another alternative embodiment of the invention, the measured region is scanned by moving the optical elements as illustrated in Figure 12. A light source 270 emits a visible light energy that is reflected from the measured region 257 of an eye 2. The light source 270 is preferably driven by a pulsed light source impeller, to produce pulses of light at a desired fixed frequency. Although less preferred, a light trimmer may be placed in the path of light from the light source 270, to produce pulsed light at the desired frequency.

A polarizer 274 may be placed between the light source 270 and an aperture 276. This polarizer 274 passes the polarized light to the aperture 276. This aperture 276 selectively passes the polarized light. This polarized light illuminates a polarization beam splitter 278. This divider 278 of the polarization beam has a reflection surface 279 which reflects the polarized light towards the eye 2. This polarized light that is reflected by the measured region of the eye 2 is generally not fully polarized when it returns to the bias light splitter 270. Thus, a portion of the light reflected from the region will pass through the divider 278 of the polarization beam. A plate comprising an optically non-transmitting material 259 is placed in the path of light passed through the beam splitter 278. An aperture 280 is formed in the optically non-transmitting material 259 and restricts a dimension through the measured region 257 by selectively passing light to a detector 281 and the non-transmitting plate optically excludes the light outside the üítÉ? ^^^ ggg | ¡| 5¡¡¿, measured region of passing to the detector. The light detector 281 converts light into a corneal edge electrical signal 122. An image forming lens 285 is positioned along the optical path between the two apertures and the eye. The lens 285, which forms images, projects the image of the aperture 276 onto the eye 2 to thereby form a focused beam of visible light energy that intercepts the eye to form a zone 202 of visible light. The image forming lens also forms an image of the measured region 257 in the aperture 280. The projected light zone 202 is aligned to thereby pass through the aperture 280 after being reflected from the surface of the eye 2. The surface of the Reflectance 279 of the polarization beam splitter 278 aligns the projected light zone 202 with the measured region 257 so that this projected light zone 202 and the measured region 257 are confocal in the eye 2. This confocal arrangement of the two apertures conveniently improves The signal-to-noise ratio of the measured signal is especially effective in suppressing the optical noise of the lights present under an operating microscope.

The measured region 257 can be swept around the path 200 with a module 282 of deflection of the light beam. This deflection module of the light beam sweeps both the projected zone 202 and the region of the eye selected by the aperture 280 of the detector. By rotating the light zone 202 and the measured region 257 around the eye at a reference frequency in a pattern comprising the annular path 200, a varying corneal edge signal 122 is generated at the reference frequency. The beam deflection module 282 comprises movable mirrors 283 and 284. Alternatively, other moving optical elements, in addition to the mirrors, such as lenses and prisms, may be used. The mirrors . 282 and 284 are mechanically coupled to galvanometers 286 and 287. Although galvanometers are used in this embodiment, any suitable impulse, such as staggering motors, servo motors and piezoelectric transducers can be employed. By suitably rotating the mirrors 283 and 284, the measured region 257 and the light zone 202 are swept around the path 200. to ... -rr ^ inflflbii? iiftttÉ In still another alternative embodiment of the invention, the visible light zone 202 is swept by the projection of a light zone comprising a beam of visible light energy from a video display in the eye, as illustrated in Figure 13. A cathode ray tube 289 comprises a screen 288, on which a light zone 292 appears. This zone 292 of light travels around path 290 on the screen of the cathode ray tube. Although the cathode ray tube is illustrated, any suitable display device, such as a super-luminescent display, liquid crystal display or active matrix display, may also be used. A lens 284 projects an image of zone 292 of light onto the eye 2, so as to form a light area 202. This light zone 202 travels around the trajectory 200. A light detector 294 is positioned to receive the light reflected by the eye 2. This reflected light is converted to the electrical signal 122 of the corneal edge by the detector 294. In another embodiment of the invention, the oo tracker also provides for automatically detecting the presence of a LASIK flag, for pressing and directing the projection model of the visible light zone, and for moving the trajectory 200 so that the position of the trajectory corresponds to the position of the eye, as illustrated in Figure 14. A measured region 257 sweeps around path 200. This measured region 257 comprises a light zone 202. Preferably, the light zone 202 is formed as illustrated above by projecting a light zone from a video screen onto an eye 2. Alternatively, other techniques, such as those illustrated above, can be used to scan or sweep the measured region. For example, a projected light zone that is confocal with the measured region, can be used. A first path 202a is substantially aligned with the limbus 10a. During a pattern portion 223 of scanning or scanning around path 200a, the light source is switched off and the data is interpolated. During LASIK, this reference portion will correspond to the underlying region 212. As the eye moves, a signal is generated, which indicates the direction and magnitude of eye movement, as illustrated above. The trajectory is displaced in the direction of eye movement, which results in a displaced trajectory 200B. The subsequent movement of the eye will result in a further displacement of the trajectory. If desired, the swept path may be oval of another configuration, such as 200c. This oval configuration can be convenient in situations where the eye moves to appear elliptical. A control circuit 300 for controlling the eye tracker and the position of the path 200 is illustrated schematically in Figure 15. This circuit will now be discussed in detail. The control circuit 300 includes a user interface circuit 302, an automatic flag detection circuit 328, a reference circuit 340, an interpolation circuit 342, a displacement circuit 330, an error detection circuit 352, an circuit 344 of the light detector, a feedback circuit 326, a computer interface circuit 368, a loop generator 324 and a CRT circuit 370. Again, again, those skilled in the art should recognize that the invention is not inherently limited to the specific arrangement of electrical, analog and digital circuits shown. For example, in some embodiments, digital data processing hardware / software systems can replace (substantially directly or with modifications) at least some of the analog functions and components of these circuits. The user interface 302 makes use of a CRT in the signal 304, electrically coupled to the generator 324 of circles. A vertical center signal 306 of circle and a horizontal center 310 of circle are electrically coupled to a feedback circuit 326. A radio signal 308 is electrically coupled to a loop generator 324. A reference automatic signal 312, a reference width signal 314, a reference start signal 316 and a LASIK in the signal 318 are electrically coupled to the automatic fin detection circuit 328. A tracking on the signal 320 and a tracking centering circuit 322 is coupled to a displacement circuit 330. The tracking in the signal 320 is also electrically coupled to the feedback circuit 326. This automatic fin detection circuit 328 is electronically coupled to a reference circuit 340, a synchronization circuit 342, the detector circuit 344 and an interpolation circuit 342. A reference synchronization signal 119 is electrically coupled to the synchronization circuit 331. A reference signal 334, a reference start signal 336 and a LASIK in the signal 338 are electrically coupled to the reference circuit 340. The LASIK in the signal 338 is also electrically coupled to the interpolation circuit 342. A signal 346 from the filtered limb of the detector circuit 344 is electrically coupled to the automatic fin sensing circuit 328. The reference circuit 340 is electrically coupled to the synchronization circuit 332 and to the interpolation circuit 342. The reference synchronization signal 119 from the synchronization circuit 332 enters the reference circuit 340. The reference synchronization signal 344 is electrically coupled to the interpolation circuit 342. The interpolation circuit 342 is electrically coupled to the detector circuit 344, the synchronization circuit 332 and the displacement circuit 330. The filtered signal 346 from the limb from the detector 344 is coupled to the interpolation circuit 342. The zone frequency signal 348 from the synchronization circuit 332 is coupled to the interpolation circuit 342 and the detector circuit 344. The filtered signal of the limb with the interpolation 340 from the interpolation circuit 342 is coupled to the displacement circuit 330. The displacement circuit 330 is electrically coupled to the interpolation circuit 342, the user interface circuit 302, the error detection circuit 352 and the feedback circuit 326. The fluctuation 354 of chalk and the average signal 356 of the limbus are electrically coupled to the error detection circuit 352. The vertical shift signal 358 and the 360 signal of The horizontal displacement is electrically coupled to the circuit 326. The error detection circuit 352 is electrically coupled to the user interface 302 and the displacement circuit 330. An error signal 362 is coupled to the user interface 302. The feedback circuit 326 is electrically coupled to the user interface circuit 302, the displacement circuit 330, the circle generating circuit 324 and the computer interface circuit 368. The signal 364 of the vertical center of the feedback circuit 326 is electrically coupled to the loop generator 324 and the computer interface 368. The horizontal center 366 is electrically coupled to the circle generator 324 and the computer interface 368. The circle generator 324 is electrically coupled to the cathode ray tube 370, the feedback circuit 326 and the user interface 302. The horizontal pulse 372, the vertical pulse 374 and the intensity pulse 376 are electrically coupled to the CRT 370.

The reference circuit 340 is illustrated schematically in Figure 15a. This circuit generates a signal reference synchronization 344, which is used to synchronize the interpolation of the measured intensity with the one disconnected from the projected light zone 202. The reference width signal 314 enters an analog-to-digital converter 378, 8 bits. The digital output of the analog-to-digital converter 378 enters as the initial count of an 8-bit 380 counter. The zone frequency signal 348 enters the 8-bit counter 380. The output of the 8-bit counter 380 enters a comparator 382 of digital magnitude. The output of digital magnitude comparator 382 enters to readjust bistable circuit 384. Reference start signal 336 enters an 8-bit analog-to-digital converter 388. The digital balance of the analog-to-digital converter 388 enters as an initial count to an 8-bit 390 counter. The reference synchronization signal 119 is input to the preload of the 8-bit counter 390, to the zone frequency signal 348 input to decrease the 8-bit counter 390. The output of the 8-bit counter 390 enters the digital magnitude comparator 392. The output of the comparator 392 enters to adjust the flip flop 384 and the precharge counter 380. The output of flip flop 384 enters gate "Y" 386. The LASIK at signal 338 enters gate "Y" 386. The output of gate "Y" 386 is reference time 344. The automatic fin detection circuit 328 is illustrated schematically in Figure 15B. That circuit is used to automatically detect the presence of an object that covers the limbus, such as the eyelid or LASIK fin. This circuit automatically adjusts the interpolation and scan or sweep of the projected zone. the presence of the fin can be detected by an abrupt change in the intensity of the measured signal, when the projected zone passes over the edge of the fin. The filtered signal 346 of the limb is input to an 8-bit digital analog converter 394. The digital output of the analog to digital converter 394 enters a microcontroller 396. The reference synchronization signal 119 enters the microcontroller 396. The auto reference signal 312 is input to the switches 398, 400 and 402. A "NO" gate 404 the opposite of the reference signal 312 enters the switches 406, 408 and 410. When the automatic reference signal 312 is true, the switches 406, 408 and 410 are open, and the switches 398, 400 and 402 are closed to produce the reference width 334A, the reference boot 336 and the LASIK in the signals 318 from the microcontroller 396. The user interface circuit 302 is illustrated schematically in Figure 15c. A reference voltage 412 is applied through variable resistors 414 to 424. The variable resistors, 414 to 424, are adjusted to produce the desired voltages for the horizontal center 310 of circle, the vertical center 306 of circle, the radius 308 of circle, tracking level 322, reference width 314 and reference start 316, respectively. The scan on the signal 320 is activated by a switch 426. The CRT on the signal is activated by closing a switch 428. The LASIK on the signal 318 is activated by closing a switch 430 and the automatic reference signal 312 is activated by closing a switch 432 A tracking error signal 434 is used to activate a red light emitting diode (LED) 434, to indicate a tracking error. The tracking error signal 362 is also input to a "NO" gate to activate a green LED to indicate tracking when the error signal 362 is not active. The interpolation circuit 342 is illustrated schematically in Figure I5d. The filtered signal 346 of the limb enters a track and support 400. The reference signal 344 of the reference time also enters the track and support 440. The output of the track and support 440 enters the interpolator 442. The filtered signal 346 of the limbus enters to the track and support 444. A "NO" gate 448 receives the reference time signal 344 and produces a voltage to an input of an attempt 446. This attempt 446 produces a voltage to the track and support 444. this track and support 444 enters the interpolator 442. The track and support 440 and the track and support 444 enter the endpoint voltages to be interpolated., among them, by inolator 442. This i ».- A» ..? - * ym¡ ^ interpolator 442 uses the input voltages from the track and support 440 and 444 to interpolate the signal between the two endpoint voltages. The interpolator 442 can be constructed from a combination of analog and digital electronic parts. Alternatively, the interpolator can be constructed from a microcontroller. This interpolator 442 also receives the reference time signal 344 as input. The zone frequency signal 348 is input to a zone frequency modulator 450. The interpolator 442 produces an interpolated voltage to the zone frequency modulator 450. When the LASIK in the signal 338 is active, the output of the zone frequency modulator 450 becomes the input to sum the blocks 452 by closing the switch 454. The filtered signal 346 of the limb is also input to the summing block 452. The output of the summing block 452 is the filtered signal of the limb with the interpolation 450. The synchronizing circuit 332 is illustrated schematically in Figure 15e. A voltage is applied to the zone frequency generator 454. This zone frequency generator is preferably a crystal oscillator, but can be any suitable oscillator, easily constructed by a person skilled in the electronics. The zone frequency generator generates the zone frequency signal 348. This signal 348 enters the 8-bit counter 456. The balance of the 8-bit counter 456 generates the synchronization reference signal 119 every 256 oscillations of the zone frequency generator 454. Therefore, there are 256 pulses of light areas 202 for each rotation of sweep region 257. The displacement circuit 330 determines the displacement of the limbus 10 relative to the trajectory 200, as illustrated in Figure 15f. The filtered signal from the limb with interpolation 350 is input to a variable gain amplifier 458. The output of this variable gain amplifier 458 is input to a synchronous demodulator 460. The output of this synchronous demodulator 460 is input to a tuneable bandpass filter 462. This tuneable bandpass filter is tuned to the rotation frequency by the input of the reference synchronization signal 119. The output of the tunable band weight filter 462 is input to a limiter 464 and a peak holder 466. The output of the limiter 464 is input to a phase comparator 468. The synchronization signal 119 is input to the phase comparator 468. The output of this phase comparator 468 is input to a track and support 470. The output of this track and support 470 is input to a sine generator 472 and a generator 474 of cosine. The output of the synchronous demodulator 460 is input to a DC / low pass filter 476. The output of the DC / low pass filter 476 is the average reflection signal 356. This average reflection signal 356 is input to a differential amplifier 478. the tracking centering level 322 is also input to the differential amplifier 478. The output of the amplifier differential 478 is input to variable gain amplifier 458. The synchronization signal 119 is input to a delay device 480. The output of the input reset 482. to a readjustment of the peak support 466 and a readjustment of the track and support 470. to output of the support 466 of cresa is the fluctuating signal. crest 354. This fluctuating crest signal 354 is input to the indicated multipliers 484 and 486. The outputs of the indicated multipliers 484 and 486 are the vertical and horizontal tracking displacements 358 and 360, respectively. The error detection circuit 352 is illustrated schematically in Figure 15g. This circuit detects tracking errors. The peak fluctuating signal 354 is input to a comparator 488. A variable resistor 490 adjusts the voltage for the upper limit 492 fluctuating peak, which is also input to the comparator 488. The average reflex signal 356 is input to a comparator 498. A resistor variable is used to adjust the "upper limit voltage 496 of average reflection, which is input to the comparator 498. A variable resistor 500 is used to set the lower limit 502 of the average reflection that is input to a comparator 504. The outputs of the comparators 488, 498 and 504 are inputs to a "0" gate 506. The output of the gate "0" 506 is input to a gate - "NO" and a setting pin of a bistable circuit 510. The output of the gate "NO" 508 is input to a reset pin of the bistable circuit 510. The output of bistable circuit 510 is to signal 362 of the tracker error. The light detector circuit 344 is illustrated schematically in Figure 15h. The reflected light is converted to an electrical signal by a photo-detector 510. The output of the photodetector 510 enters an amplifier 512. The output of the amplifier 512 is "input to a tuneable bandpass filter 514. The frequency signal 348 zone is input to the tuneable bandpass filter 514. The zone frequency signal 348 selectively tunes the bandpass filter 514 to the zone frequency.The output of the tuneable bandpass filter 514 is the filtered signal 346 The feedback circuit 326 is illustrated schematically in Figure 15i, The horizontal center signal 310 of the C is input to an adder 516. The horizontal tracking movement 360 is input to an amplifier 518. The output of the amplifier 518 is input to a switch 520. Scanning on signal 320 closes switches 520 and 522. Vertical center signal 306 of CRT is input to summing block 524. Vertical shift The scanner 358 is input to an amplifier 526. The output of the amplifier 526 is input to the switch 522. When the tracking on the signal 320 is active, the summing block 510 adds the output of the amplifier 518 with the horizontal center signal 310 of the CRT The output of the summing block 516 is the signal 366 of the horizontal display center. Likewise, when the tracking on the signal 320 is active the output of the amplifier 526 is added with the signal 306 of the vertical center of CRT by the summing block 524. The output of the summing block 524"is the signal 364 of the vertical display center. The circuit of the CRT is illustrated schematically in Figure 15J.An intensity pulse signal 376 is input to a CRT to control the intensity.A horizontal pulse 372 is connected to the CRT to control the horizontal position of the sweep zone. vertical 374 enters the CRT to control the vertical position of the sweep zone.

The circle generator circuit 24 is illustrated schematically in Figure 15k. The zone frequency signal 348 is input to an 8-bit counter 530. The output of the 8-bit counter 530 is input to a cosine ROM 532, the output of the cosine ROM 532 is input to a digital-to-analog converter 534. The output of the digital converter in analog "is input to the multiplier 536. The output of the multiplier 536 is input to a summing block 538. The signal of the horizontal center 366 of display is input to the summing block 538. The output of the summing block 538 is the horizontal pulse 372. The output of the 8-bit counter 530 is also input to the sine ROM 540. The output of the sine ROM 540 is input to the digital converter 542 in analog.The output of this digital converter 542 in analog is input to multiplier 544. Radio 308 is also input to multiplier 544. Output of multiplier 544 is input to summing block 546. Vertical display center 364 is also input to summing block 546. Output of summing block 546 is vertical pulse 374. The reference time signal 344 is input to a "NO" gate 548. The output of the gate "NO" 548 of input to a gate "Y" 550. The frequency signal of zone 348 and the CRT in the signal 304 are also input to a "Y" gate 550. the output of the gate "Y" 550 is the intensity pulse 376. The computer interface circuit 368 is illustrated schematically in Figure 151. The analog signal 364 of the vertical center is input to an analog to digital converter 552. The output of the 552 analog to digital converter is the vertical 554 digital center. The analog signal 366 of the horizontal center is input to the analog-to-digital converter 556. The output of the analog 556 converter in digital is the signal 558 of the digital horizontal center. Referring now to Figures 14, 16 and 17, an alternative method for tracking the relative motion of the eye, when the limb of the eye is partially covered, will now be described. The method includes automatically detecting the presence of a LASIK fin, the pulse and reference of the projection of a visible light zone, and moving the trajectory 200 so that the position of the trajectory corresponds to the position of the eye, as shown in FIG. illustrated in Figures 14, 16 and 17. As illustrated above, this limbus covering can occur by an eyelid covering the limbus during normal vision, or it can occur during a surgical procedure, such as LASIK. Again, a zone of visible light is projected to be confocal with a region measured in the eye. Alternatively, a zone of infrared light can be projected to be confocal with the measured region of the eye. This measured region 257 and light zone 202 are swept around the eye, as illustrated in Figure 14. The method also includes restricting a dimension across the measured region by selectively passing light rays from within the region to a detector. of light energy and excluding light rays from outside the region of the light energy detector. In addition, a beam deflection module deflects this beam with a mirror, prism or lens. Alternatively, a zone of light in a display can be projected onto the eye, and the light zone projected from the display is swept around the eye. The method encompasses scanning the light zone on an annular path 200. The measured region 257 comprising the light zone 202 is swept in sequence around a path 200. The light zone 202 is discounted during a reference portion 223. of trajectory 200. The intensity of the reflected light is interpolated between the measured values of the reflected light energy. A limbus 10 of the eye 2"is initially placed in A. the trajectory 200 is aligned with the limb 10 in position A, as illustrated in Figure 16. The measured region 257 has a dimension 560 across the measured region. The eye 2 and the limbus 10 move to thereby generate a displacement of the limbus relative to the trajectory 200. This trajectory 200 is moved from an initial position to the moved position of the limbus 10. The further movement of the limbus 10 will place the limbus in B. A shifted measured region 257 'is swept in sequence around a shifted path 200' in position B. A distance 562 of separation between positions A and B is greater than a dimension 560 through a measured region 257. During the sweep of a zone 202 of visible light around the trajectory 200, this zone of light is pulsed. The desired frequency may vary from 0.5 to 500 kHz, and is preferably about 100 kHz. The light zone 202 is pulsed while sweeping around the eye, as illustrated in Figure 16. Pulsing the light zone will overlap the positions of the light areas of maximum intensity, such as 559a to 559f, around the trajectory 200. Regions measured in sequence, such as 257a to 257f, are formed by pulsing the light zone 202 to form light areas of maximum intensity, such as 559a to 559f. The light areas of maximum intensity overlap so that the measured regions that comprise the zones overlap. For example, a measured region, such as 257c overlaps with the adjacent measured regions 257a, 257b, 257d and 257d. The pulsing of the light area 202 is synchronized with the sweep, so the number of pulses that 13 ' occur during a rotation of the light zone 202 around the trajectory 200 remains constant Each rotation around the trajectory has a first pulse, and the angular separation of a pulse that occurs in sequence, remains fixed in relation to the first pulse of rotation around the path. Each rotation of the light beam 202 around the path 200 will generate a signal at a reference frequency, that reference frequency thereof as the rotation of the area 202 around the path 200. This reference frequency can also be called as the frequency of rotation in which the beam rotates around path 200. Pulsing the zone of z 202 will produce a carrier signal at the frequency of the pulsed light zone. The carrier signal is modulated in amplitude by the reflected light from the measured region 257 according to the measured region 257 and the light zone 202 revolve around the path 200. The demodulation of the amplitude-modulated signal at the carrier frequency will produce a Signal with AC and DC components. A variable AC component will occur at the reference frequency and a DC component will occur and correspond to the average reflected intensity. A phase angle of the variable AC component is compared to the reference to determine an angle of eye displacement. The magnitude of the variable signal is compared to the reference to determine the magnitude of the displacement of the eye. As the limbus 10 moves from position A to position B, the sweep is performed so that the limb remains within at least a portion of the measured region 257, as illustrated in Figure 17. For example, the limbus 10 is initially placed at A and is aligned with path 200. The displacement of limbus 10 to position 564 will cause slight misalignment of the limb with path 200. This slight misalignment causes a variation of signal at the reference frequency. By comparing an amplitude and a phase of the variable signal with a reference, the position of the eye relative to the trajectory 200 is determined. This trajectory 200 is displaced so as to be aligned with the displaced position 564 of the limbus 10. Further movement of the limbus 10 to the displaced position 566 will cause the trajectory 200 to move further and be aligned with the displaced position 566 of the limbus 10. This aligning the path 200 with the displaced position 566 of the limb will minimize the variation in the intensity of the reflected light energy. During displacement of the limbus 10, the trajectory 200 is displaced and aligned with the limbus before this limbus 10 moves to the outside of the measured region 2257. In an exemplary embodiment, the eye tracker is integrated with an ultrasound scanning system. laser surgery, as illustrated in Figure 8. This laser system 574 is used to mold the anterior surface of an eye to a predetermined configuration. The delivery system 574 of the scanning laser includes a laser beam configuration module 577 placed in the path of an ablative laser beam 578. This, laser beam configuration module 577 selectively passes this laser beam through a variable aperture. 576. One dimension of the variable aperture 576 is switched between pulses of the laser beam 578 for $ 6 vary the configuration of the laser beam in the eye. The beam configuration module 577 can be rotated to thereby rotate the variable aperture 576 around the eye 2. This laser beam configuration module 577 is controlled by the impeller control circuitry 605. The laser scanning system 574 further includes a laser beam deflection module 580, which is used to shift the path of the laser beam between the pulses of this laser beam 578. The beam deflection module 580 includes two rotating mirrors 582 and 584 to move to position of the path of the laser beam. That deflection module 580 of the beam also includes mechanical impellers "suitable for moving the mirrors., the beam deflection module may include other optical elements for deflecting the laser beam, such as prisms and moving lenses. The mechanical drivers of the beam deflection module 580 are controlled by the drive system 605 of the impeller control. A lens 586 that forms images is placed in the path of the laser beam. This image lens 586 forms the image of the aperture 576 near the eye. A beam splitter 588 selectively reflects the energy of the laser beam and transmits visible and near infrared light energy to an operating microscope 590. 5 The eye tracking subsystem includes a sweep light zone 592 from a screen 288 of a cathode ray tube 289, which projects onto the eye. The light zone 292 travels around a trajectory 290 on the screen of the cathode ray tube. Although a tube is used of cathode ray, any suitable display element, such as a super-luminescent display, a liquid crystal display or an active matrix display can also be used. A lens 592, which forms images, is positioned to project area 292 over eye 2. A divider 588 of beams couples the tracking system of the eye with the laser delivery system. OR? 594 light collection lens is placed in front of the light detector 294. This light collection lens 594 preferably forms an image of the eye 2 on the detector 294. The reflected light is -SESSIONS converts an electrical signal 122 from the corneal edge to the detector 294. The presence of the fin 210 is automatically detected as described above. During a sweep portion of the measured region 257 around the path 202, the light zone 202 is turned off on the reference portion 223 of the path 200. This reference portion 595 of the video path 290 corresponds to the portion 223 reference reference 200. This reference region provides visual feedback to the surgeon that the superimposed fin of the tissue has been accurately detected Other elements are preferably integrated with the laser surgery system 574, such as an operating microscope 590 and an objective system 596 for visual fixation A mirror 598 is placed between the apertures of the objective lens, 600 and 602, of the microscope 590. The mirror 598 reflects the light from the tracking system and objective of the eye's visual fixation towards the eye. this eye 2. The microscope 590 preferably allows to see the path 200 of the measured region 257 around the eye 2. A selective light beam splitter 604 the light of predetermined wavelengths from screen 288 of the CRT, and selectively passes light of predetermined wavelengths from the visual fixation system 596. This 596 system of visual fixation provides a goal for the patient to see during surgery. Although this embodiment of the invention employs an eye tracker, which includes a scan zone from a CRT screen, alternative embodiments of the invention will include other methods suitable for scanning a measured region 257, as illustrated below. The laser system 574 includes a controller, as illustrated in Figure 18a. This 606 controller of the laser system includes a random access memory (RAM) 608, a tangible means 610, a data collector 612, a microprocessor 614, a data gate 616, a circuit 605 of impeller control and an eye tracking interface 620. That tangible medium can comprise any suitable means readable by computer, such as a read-only memory (ROM). a diskette or hard disk drive, or the like. The RAM is configured to include a laser treatment table 622, which is stored, at least partially, in the RAM, during the laser treatment. Preferably, the laser treatment table is stored in the RAM before the treatment, to avoid the delays caused by the calculation of the laser treatment during the treatment. The eye tracker interface 620 brings the position of the eye into the controller 606 of the laser system. An initial 624 position of the eye is stored in the RAM 608 at the start of the laser treatment. This laser treatment table 622 includes numbers corresponding to the positions and configurations of the laser beam 578 in the eye, during laser pulsation. The laser treatment table includes several registers 626. The registers in the laser treatment table list the laser configuration during the discrete pulses of the laser beam. The laser treatment table 622 includes the fields for a displacement X 628 and a displacement Y 630 of the laser beam from a laser treatment center. In this laser treatment table the displacements are listed as the X and Y coordinates relative to the treatment center, but any suitable coordinate system can be 'used. The treatment table also includes fields for the variable aperture diameter 632, the width 534 of the variable aperture slit and the angle 636 of the variable aperture slit. The laser treatment table 622 also includes a field for the number of pulses 635 for each register 626 of the laser treatment table 622. A flowchart, illustrating a computer routine 637 for treating the patient with a laser beam, is shown in Figure 18b. The routine includes the entry of the parameters of the laser treatment to the patient, such as the prescription of the patient's glasses. These parameters are input to the controller 606 of the laser system, by the data input / output port 616 and stored in the RAM 608. The laser system controller calculates the laser treatment table 622 and stores the table in the RAM 608. A surgeon aligns the patient's eye 2 with the laser system 574. By activating a switch or other input device, the surgeon then indicates that the patient is aligned. The surgeon initiates the laser treatment by pressing a foot switch or other input device. Alternatively, starting the laser treatment, the surgeon could indicate that the patient is alindo. The eye tracker determines the initial 624 position of the eye when the surgeon indicates that the patient is aligned. This initial 624 position of the eye is stored in the RAM of the computer, as illustrated by the variables XINIT and YINIT, which correspond to the positions of the initial coordinates X and Y of the eye. These coordinate positions of the eye are preferably far from the laser treatment center. The current position of the eye is determined by access to the gate 620 of the tracker interface. The current position of the eye is stored in the RAM as illustrated by the variables XCUR and YCUR corresponding to the current X and Y coordinates of the eye. For the first laser pulse, the initial position of the eye can be considered the current position of the eye. The vector of the displacement between the initial position of the eye and the current position of the eye can be represented illustratively by the variables XDIS and YDIS for the displacements X and Y, respectively. The values of XDIS and YDIS are calculated by subtracting the initial position designated by the coordinate reference (XINIT, YINIT) from the current eye position designated by the coordinate reference (XCUR, YCUR). The displacement vector designated by the coordinate references (XDIS, YDIS) is compared to a threshold tolerance. If the displacement vector is greater than the tolerance, the treatment is paused and an alarm can be activated. If the displacement vector is smaller than the threshold, the displacement vector between the initial and current eye positions is used to calculate the new position shifted for the next laser pulse.

The new displacement positions, X and Y are designated by the coordinate reference (XNEW, YNEW). The values of XNEW and YNEW are calculated by adding the displacement vector (XDIS, YDIS) to the original offset position (XOFFS, YOFFS of the current record in the treatment table 622. Laser elements are configured as indicated by the registration current of the treatment table and the new offset positions of X and Y, XNEW and YNEW, respectively The laser is pulsed The computer routines to determine the current eye position through a computer routine to press the laser, are repeated until the last pulse indicated by the treatment table has been delivered, as illustrated in Figure 18b.In an alternative mode of an eye tracker, integrated with a laser scanning system, the deflection module The beam of the scanning laser system can be used to scan the measured region 257 about a path 200, as illustrated in FIG. 19. The integrated system 638 includes a module. or 577 of laser beam configuration, to define a variable aperture 576, a laser beam 578 and a laser beam deflection member 580, which is used to displace the path of the laser beam. This deviation element 580 of the laser beam is also used to scan the measured area 27 around a path 200. A beam splitter 639 intercepts the laser beam 578 and the pulsed light from the light source 270. The beam splitter 639 selectively passes the laser beam 270 'and reflects the pulsed light from the light source 270. Alternatively, the beam splitter 639 can selectively reflect the laser beam 27-0 and pass light from the light source 274. The beam splitter 639 aligns the openings 276 and 280 with the variable aperture 576. The openings 576, 276 and 280 are concentric when they form images on the eye2. As the laser treatment proceeds, the image of the variable aperture 276 is scanned according to the laser treatment table 622. Between the pulses of the laser beam 578, the openings 276 and 280 scan the measured region 257 around a path 200. A method of ablating a moving eye with a laser system, such as the 574, is illustrated in FIGS. and 21. The eye is laser-shaped to a predetermined configuration, with a series of pulses from a beam of an ablative laser energy. A grid 640 indicates the center 641 of an attempted laser treatment area 642. This attempted laser treatment area 642 is aligned to thereby remove the cornea 12 to a desired configuration within the attempted laser treatment area 642. The position of the eye is determined with a sweep light zone 202, as described above. An initial trajectory 200a of the sweep light zone 202 and the swept measurement region 257 is aligned with the initial position of the limb 10a. An area 642 of attempted laser treatment is aligned in relation to an initial position of a limbus 10a. A fin of the cut tissue LASIK that covers the limbus is detected automatically, and the visible light beam is directed on the fin, as described above. An attempted laser treatment area 642 is eccentric with the limbus 10a, as illustrated in Figure 20. The attempted laser treatment area 642 will be treated with a plurality of individual laser pulses, such as a single laser pulse 646. The trajectory 589 of the displaced laser beam is displaced during the laser beam pulse 646. The individual laser pulses are of variable size and displaced position, as indicated by table 622 of laser treatment. This laser treatment table 622 lists the attempted displacement positions of the laser beam relative to the reference position 644. The reference position 644 is preferably located at the center 641 of the attempted treatment area 64a, but may alternatively be located away from the center 641 of the treatment area 642 attempted. An attempted displacement vector 648 illustrates the attempted displacement position of the single laser pulse 646 relative to the reference 644. The attempted displacement vector 648 will comprise both a position of a displacement X 628 and a displacement Y 630 of the block 622 of treatment. ^^^ iagggÉlgj During laser surgery, the eye will typically move between the moment the patient is aligned with the laser and the moment the laser pulse is delivered. A moved limb 10b of the eye is aligned with a moved path 200b. A distance 660 of separation between the initial position 10a of the limbus and a moved position 10b of the limbus, which exceeds a dimension 658 through the measured region 257. The axis of the eye tracker and the path of the laser beam can move independently . An initial position of the axis of the tracker 651 of the eye is shifted to a current position of the axis of the tracker 653 of the eye. When the patient is aligned with the laser, an initial position of the eye 650 is determined. This initial position of the eye 650 is stored in the RAM 608 of the controller 606 of the laser system. Prior to ablation, an individual laser pulse attempted, such as 646, a current position of eye 652 is determined. A displacement vector 654 of the eye is calculated by subtracting the initial position 650 of the eye from the current position 652 of the eye. This eye displacement vector 654 is compared to a maximum displacement tolerance. If the displacement vector 654 is greater than the tolerance, the laser system controller 606 pauses the laser treatment. If the displacement vector 654 is smaller than the maximum displacement tolerance, the laser system controller 606 calculates a new displacement position 656, based on the displacement positions X 628 and the displacement Y 630 of the current record 626 of table 622. of treatment. The configuration and displacement elements of the laser beam are moved to the new positions, indicated by the position 656 of the new displacement and the other fields 632 to 636 of the current record of the laser treatment table. The current record of the laser treatment table can be any record of the laser treatment table, such as the registration number 4. The laser beam 578 is pulsed according to the pulse field 635 of the current register of the laser treatment table 622.

After the laser is pulsed, the step of determining the current position of the eye and the subsequent steps leading to the pulsation of the laser beam 578 are repeated. After all laser pulses, indicated by treatment table 622, have been delivered, this laser treatment ends. It should be understood that, although the present invention has been generally described in its use with a scanning or scanning laser system, which includes an ultraviolet laser for ablation of the surface of an eye, this invention is not limited to this type. of system. For example, the systems and methods described herein can be used in conjunction with a laser system which employs other suitable wavelengths of electromagnetic radiation, such as electromagnetic radiation from the infrared portion of the electromagnetic radiation spectrum. While the foregoing is a complete description of the preferred embodiments of the invention, various alternatives, modifications and equivalents may be used. For example, the present invention could be used with a scanning laser system, such as the T-PRK® scanning and scanning laser system from Autonomous Technologies Corporation, or the Keracor ™ 217 scanning laser system from Chiron Vision, as with large-area ablation laser systems. Therefore, the above description should not be construed as limiting the scope of the invention, which is defined by the following claims.

Claims (19)

1. RE IVI N D I CAC I O N S 1. An optical system, to track the movement of a patient's eye, this system comprises: a light source; an optical train, to direct a ray of light, from the light source, to a region of the eye, which includes the sclera and the iris; a light detector, positioned to receive light reflected from said region of the eye; and a controller, coupled to the light detector, for measuring the intensity of the reflected light and determining the relative position of the eye.
2. 2. The optical system of claim 1, further comprising: a light steering system, positioned along the optical train, this light steering system is positioned along the optical train, the light steering system is configured to scan or sweep the light beam in an annular path around the pupil of the eye, the controller comprises an electrical system, coupled to the light detector and configured measurement signals, corresponding to the intensity of the light reflected from discrete portions of the eye. the annular path.
3. 3. The optical system of claim 1, wherein the light source is configured to direct an annular pattern of light on the eye, at or near the limbus, the controller comprises an electrical circuit coupled to the light detector, for measuring the signals that correspond to the intensity of the light reflected from the discrete portions of the annular light pattern.
4. 4. The optical system of claim 2, wherein the light steering system comprises oscillating mirrors, placed between the light source and the eye, and a motor for oscillating these mirrors, so that the light is swept around the path cancel.
5. 5. The optical system of claim 2, wherein the light steering system comprises a ring of light sources, placed in an annular arrangement, so that sequential activation of the light sources causes light to be swept around of the annular trajectory.
6. 6. The optical system of claim 2, wherein the light steering system comprises one or more optical fibers, coupled to * the light source, for transmitting light therethrough, these optical fibers have an end portion, for projecting the light on the oo, and an impulse to rotate the end portion of the optical fibers, to sweep the light around the annular path.
7. 7. The optical system of claim 2, further comprising: a calibration system, coupled to the light direction system, for placing the annular path substantially substantially coincident with the limbus.
8. 8. The optical system of claim 2, further comprising: a reference synchronization system, for sweeping a light beam on a reference light detector at a reference frequency and a reference intensity, and an electrical system for generating a alternative signal, which has a reference phase and a reference amplitude, based on the reference frequency and the reference intensity.
9. 9. The optical system of claim 8, wherein the electrical system is coupled to the light detector, to generate a signal from the edge of the cornea, which has a corneal edge phase and an edge amplitude of the cornea, based in a phase and an amplitude of the signals from the reflected light, this electrical system also comprises a phase comparator, to compare the faith of the reflected light signal with the reference phase, to determine an angle of the displacement vector of the eye , and a comparator of the amplitude to compare the amplitude of the signal of the reflected light with the reference amplitude, to determine a magnitude of the displacement of the eye.
10. 10. The optical system. of claim 1, further comprising a laser assembly, for projecting the radiation onto a selected region of the anterior surface of the cornea, to effect ablation of this selected region at a certain depth.
11. 11. The optical system of claim 1, further comprising: an optically non-transmitting material, with an aperture formed in the material, to restrict a dimension across the region, to selectively pass light reflected from the region through the aperture of the detector, a material that blocks the light rays from the outside of the opening, in order to define a measured region.
12. 12. The optical system of claim 11, further comprising a lens that forms images, to form the image of the region on the aperture.
13. 13. The optical system of claim 1, wherein the light source comprises a visible light source, to obtain light energy, and wherein the image forming lens projects the light energy onto the eye, as a zone of visible light.
14. 14. The eye tracker according to claim 11, wherein the optical train comprises a deflection module of the light beam, to sweep the light beam and the region measured around the eye, in an annular path, and a reflection surface, to align the projected area of light with the measured region, in order to be confocal over the eye.
15. 15. An eye tracker, to measure a position of an eye, this eye has - a limit, the tracker comprises: a light source to obtain light energy; a light detector, positioned to receive the light energy reflected from a region of the eye, this region includes a portion of the limit; an optical train, to sweep the region over the o o; and a controller, coupled to the light detector, to automatically detect a tissue that covers the boundary, and measure the light energy reflected from an uncovered portion of the boundary, to determine a relative position of the eye.
16. 16. The eye tracker of claim 15, further comprising a lens, which forms images, to project the light energy onto the eye, as a visible light zone, this light energy comprises the visible light energy; an optically non-transmitting material, with an aperture formed in the material, to restrict a dimension through the measured region, selectively passing the light energy from the region through the aperture to the detector, this material blocks the light rays from the outside of the measured region; 6366363 a deflection module of the light beam, to sweep the area of light and the region measured around the eye in an annular path; a reflection surface, to align the projected area of light with the measured region, in order to be confocal on the eye; a reference circuit for the reference of a visible light area projected onto the detected tissue that covers the limit, this limit comprises a portion of the limbus; an automatic fin detection circuit for detecting a fin of a cut tissue; an interpolation circuit, to interpolate the energy of the measured light, - and a displacement circuit, to displace an annular path to match the position of the eye.
17. 17. The eye tracker of claim 15, wherein the light source comprises an exhibit screen.
18. The eye tracker of claim 17, which comprises: a lens, which forms images, to project the light energy onto the eye, as a 'zone of visible light, this light energy comprises a visible light energy; a reference circuit, to refer the area of visible light projected onto the tissue that covers the limit, this limit comprises a portion of the limbus; an interpolation circuit, to interpolate the measured light energy; and a displacement circuit, to displace the annular path to coincide with the position of the eye.
19. 19. The eye tracker of claim 15, further comprising: a laser for generating an ablative laser energy beam; a mobile laser beam path, which is variablely displaced from a reference position; in that the controller determines a tracker axis of the mobile eye, this axis of the eye tracker can be moved by the controller, so as to coincide with the position of the eye, the tracker axis of the eye can also be moved independently in relation to the route of the laser beam; and a laser system controller, for moving the laser beam path according to a position of the eye tracker axis and the value of a laser treatment table.