HK1174521A - Purkinjie image-based alignment of suction ring in ophthalmic applications - Google Patents

Description

Purkinje image based alignment of suction ring in ophthalmic applications

This application claims the benefit of priority from U.S. provisional application No. 61/300,125 entitled "purkinje Image-based alignment of an inhalation Ring in purkinje images in Ophthalmic Applications," filed 2010, 2/1 (e) (1), said provisional application being incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a method and system for aligning and attaching a suction ring to a patient's eye during ophthalmic applications.

Background

An important factor in achieving optimal refractive results during intraocular lens (IOL) implantation, particularly for accommodating or pseudo-accommodating IOLs, IOLs that correct for spherical aberrations, or toric IOLs, is a well centered anterior capsule incision. This is because the surgeon uses the location of the capsular bag opening as a visual marker for centering the IOL. Centering is important in both optical and mechanical terms. Optically, if the IOL, cornea and fovea are not properly aligned with respect to their centers of curvature, image quality can be aberrated, while mechanically, if the IOL is not centered with respect to the lens capsule equator, the lens may tilt or become more easily displaced over time, causing optical aberrations or requiring a secondary procedure to implant or recenter the IOL.

Currently, the anterior capsule opening is manually torn using a procedure known as Continuous Circular Capsulorhexis (CCC). The opening can also be centered as done manually, using the enlarged pupil as a reference, without any other visual markings. Since, in general, the pupil is known to enlarge significantly asymmetrically, current procedures, if successfully completed, tend to systematically decenter the IOL relative to the eye's line of sight and optical axis.

Ideally, the IOL would be centered on the visual axis; however, this cannot be determined intra-operatively. An alternative placement that can be determined and allows for near-natural placement of the IOL is to center the IOL such that the optical axes of the IOL and the cornea are collinear. If the anterior capsulotomy incision can be positioned concentrically around the optical axis of the cornea and lens, i.e., so that the optical axis of the eye is maintained after implantation, then an IOL implanted and centered over the capsular opening will be positioned close to optimal.

Disclosure of Invention

One aspect of the present invention relates to an alignment device that includes means for releasably attaching a suction ring and means for applying a pattern of light to a patient's eye. The alignment device further includes means for detecting light reflected from the eye and determining whether the suction ring is aligned with the eye based on the detected light.

A second aspect of the present invention relates to an alignment device, comprising: a housing having a mechanism for releasably engaging the suction ring; and a light source connected to a plurality of lights, the lights being arranged in a pattern such that the lights apply light to a patient's eye in the pattern of light. The device further includes a detector that detects light reflected from the eye and determines whether the suction ring is centered on the eye based on the detected light.

A third aspect of the invention is directed to a method of aligning a suction ring on an eye, the method comprising positioning a suction ring over a patient's eye and applying a pattern of light to the eye. The method further includes detecting light reflected from the eye and determining whether the suction ring is aligned with the eye based on the detected light.

One or more aspects of the present invention improve the visual performance of cataract surgery by enabling more precise and proper placement of the IOL, thereby reducing optical aberrations of the eye.

Drawings

The accompanying drawings are incorporated herein and constitute a part of this specification and, together with the general description given above and the detailed description given below, serve to explain features of the invention. In the drawings:

FIG. 1 is an exploded view of an embodiment of an alignment device according to the present invention;

FIGS. 2A-2I illustrate various possible off-axis images formed by the alignment apparatus of FIG. 1;

FIG. 3A shows one possible on-axis image formed by the alignment apparatus of FIG. 1; and

fig. 3B to 3D show individual images of the fourth, first and third purkinje images, respectively, formed by the alignment device of fig. 1.

Detailed Description

The present invention relates to a method and system for aligning and attaching a suction ring to a patient's eye during ophthalmic applications involving the use of laser systems. Examples of possible laser systems that may be used with the present invention are the laser systems described in the following U.S. patent applications: 11/337,127 No; 12/217,285 No; 12/217,295 No; 12/509,412 No; 12/509,021 No; 12/509,211 and 12/509,454, each of which is incorporated herein by reference in its entirety.

Such laser systems may use an associated Patient Interface Disposable (PID) device to align and immobilize the patient's eye relative to the laser, enable efficient delivery of the treatment laser to the cornea and lens, and enable images of the laser processing to be provided to the user to monitor the progress of the procedure. Like other ophthalmic ultrashort pulse lasers used to cut corneal or lens tissue, a PID has two parts: a suction ring that is manually applied to the patient's eye; and a docking portion that is first attached to the laser and then guided via a joystick-controlled three-axis motion control system to dock the laser with the suction ring on the eye.

According to the present invention, a purkinje reflection based alignment device 100 is used with a laser system, such as those previously described, that allows the suction ring 102 to be centered about the optical axis of the eye. As discussed above, such centering will allow the implanted IOL to assume optimal placement. As shown in fig. 1, the device 100 includes a two-piece handle 102 that houses a plurality of internal batteries 104 and a syringe 106 for providing vacuum to a suction ring 134. The battery 104 powers a semicircular light source that contains several light generators, such as LEDs (light emitting diodes) 112, that are activated when a switch (not shown) is turned on. Ideally, the LED 112 is infrared, so it is not visible to the patient, but visible LEDs may also be used. The holder 114 for the LED 112 has a flange 120 with a mounting hole 124 on the flange 120, which holds the LED 112 in its correct position to be aimed through the center of a conical holder 130 and a suction ring 134, which suction ring 134 is attached to the distal end of the conical holder 130 at the beginning of the procedure. The upper edge 132 of the conical holding device 134 is attached to the underside of the semi-circular housing 122 holding the LED 112. As described below, an inspection device, such as a camera 128 or inspection lens, may be used to view an image of the patient's eye. In the case of the use of the camera 128, the camera and its associated camera lens are mounted so that the axis of the camera lens is collinear with the axis defined by the center of the suction ring 134 and the center of the semicircular ring of the LED 122. Camera images of the eye as viewed through opening 116 of holder 114 and through the center of suction ring 134 are displayed on a separate monitor (not shown).

In use, the device is held by the handle 102 and positioned over the eye because the surgeon is to view an image of the eye on a monitor. If the patient does not experience a posterior bulbar block or otherwise immobilize the eye, the patient will be instructed to look straight forward or to stare at a distant fixation light (not shown) that is visually within the open circle defined by the semicircular purkinje light source but not connected to the device 100. This is to keep the patient fixed in a relatively constant orientation so that the device 100 can be properly positioned relative to the fixed orientation. If the LED 112 emits visible light, it is helpful to have the fixation light (not shown) have a different color, which may make it easier for the patient to stare at the fixation light without being distracted by the LED 112.

When the device is close enough to the eye, purkinje reflections from the posterior surface of the lens (fourth purkinje image), the anterior surface of the cornea (first purkinje image), and the anterior surface of the lens (third purkinje image) will form and be imaged on the monitor, as shown in fig. 3B-3D, respectively. When the suction ring 134 is perfectly aligned, i.e. the camera axis is in line with the optical axis of the eye, the purkinje reflections corresponding to the first, third and fourth purkinje images will occur simultaneously, as shown in fig. 3A. Each of the three purkinje reflections in fig. 3B-3D appears as a half circle. The first purkinje reflection and the fourth reflection appear as a semicircular array of reflected LEDs "facing" each other; the opposite (convex rather than concave) curvature of the cornea compared to the posterior surface of the lens is the inversion of one of the images so that the one image "faces" the other. The third purkinje image is oriented similarly to the first purkinje reflection because the direction of curvature of the two surfaces is the same. The size of the individual LED images in the various Purkinje reflections and the different diameters of the semi-circles are a function of the geometry of the measurement angles, i.e., the distances and angles between the LED 112 and the various eye surfaces and the radii of curvature of the cornea, anterior lens surface and posterior lens surface. However, it is important for the alignment to be the location and orientation of the semi-circular reflection rather than the diameter of the semi-circle or the appearance of the individual LED reflections. To figure out how the purkinje reflections help the surgeon properly align the suction ring with the eye, the purkinje reflections are depicted in fig. 2A-2I as the eye looks left, right, up, and down relative to the axis of the suction ring. By looking at the orientation and position of the purkinje reflex displayed on the camera monitor, the surgeon can empirically adjust the position and angle of the hand-held device 100 of fig. 1 so that the suction ring 134 is properly aligned with the optical axis of the eye. When the purkinje reflex of fig. 3A is shown, it is indicated that the optical axis of the suction ring 134 is collinear with the optical axis of the eye. When proper alignment is achieved, the suction ring 134 is pressed against the eye by actuating a latch (not shown) outside the body of the handle 102 to allow a spring (not shown) to actuate the spring-loaded syringe 106. Specifically, the syringe 106 is compressed (the syringe plunger is retracted all the way inside) before the latch is actuated. Upon actuation of the latch, the spring pushes the syringe plunger outward, creating a vacuum inside the syringe 106 and, through a conduit (not shown), in the suction ring 134. Creating a vacuum in suction ring 134 causes the suction ring to clamp onto the eye. The hand-held device 100 of fig. 1 is then released from the suction ring 134 and removed. If there is little friction fit between the suction ring 134 and the conical holding means 130, the release can be achieved by simply pulling the hand-held device 100 from the suction ring 134 (the suction ring 134 is now attached to the eye). Alternatively, the conical holding device 130 may include a mechanism (not shown) that releasably engages the suction ring 134. A release lever (not shown) on the handle 102 may be in mechanical communication with the release mechanism such that upon activation of the release lever, the suction ring 134 is released.

After the suction ring is aligned with and attached to the eye, the surgeon moves the joystick to interface the snap ring at the distal end of the lever arm with the suction ring 134. When the locking ring is interfaced with the suction ring 134, they together constitute a Patient Interface Device (PID). The PID aligns and immobilizes the patient's eye with the laser during treatment, and thus the PID enables the treatment laser to be effectively delivered to the cornea and lens, as well as enables images of the laser processing to be provided to the user to monitor the progress of the procedure. Examples of such PIDs are disclosed in provisional Applications filed by the Applicant at attorney docket Nos. 12212/66 and 12212/69, filed at 29/2010 and 2/2010, 1/12212/69, respectively, each entitled "Servo Controlled Docking Force Device for Use in ophthalmic Applications," which are incorporated herein by reference in their entirety.

Note that the application of a patient interface device having any form of flattening or bending affects the shape and axis of the cornea, and thus it is simply not possible to determine the optical axis of the eye once the patient interface device is applied. Therefore, if the suction ring 134 is to be applied such that it is centered on the optical axis, the optical axis must be determined before the suction ring 134 is applied.

While the above process is described in relation to a hand-held device 100, purkinje-based devices may also be built into a joystick-controlled three-axis motion optical head in an ophthalmic laser. In this case, the image of the purkinje reflection would still be used to determine when the suction ring is centered, however, the patient's eye or head and the optical head of the laser would need to be manipulated to obtain the best positioning of the suction ring on the eye.

Note that for the anterior capsulotomy cut with the laser, the location of the lens capsule must be determined because the capsulotomy cut is made transcapsulally. This determination may be made using a measurement system based on a Scheimpflug camera. The measurements can likewise be made using optical coherence tomography or other equivalent methods. If the suction ring 134 is well centered on the optical axis, the apex of the lens, i.e., the highest elevation point along the optical axis of the laser, will fall on the optical axis of the lens. A circular anterior capsulotomy cut can then be made around the apex.

If the suction ring 134 is not centered and the central region of the lens is assumed to be very spherical, the apex of the lens will not fall on the optical axis. In this latter case, there is no good way to determine where the anterior capsulotomy cut should be made. If the circular cut is centered on the apex of the lens, which is tilted with respect to the axis of the laser, the cut will be off-center with respect to the optical axis of the eye, and if the IOL is centered as is commonly done with reference to the capsulotomy, the IOL will then also be off-center.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims (3)

1. An alignment device, comprising:

means for releasably attaching a suction ring;

means for applying a pattern of light to a patient's eye; and

means for detecting light reflected from the eye and determining whether the suction ring is aligned with the eye based on the detected light.

2. An alignment device, comprising:

a housing including a mechanism to releasably engage the suction ring;

a light source connected to a plurality of lights, the lights being arranged in a pattern such that the lights apply light to a patient's eye in the pattern of light; and

a detector that detects light reflected from the eye and determines whether the suction ring is centered on the eye based on the detected light.

3. A method of aligning a suction ring on an eye, the method comprising:

positioning a suction ring over an eye of a patient;

applying a pattern of light to the eye; and

detecting light reflected from the eye and determining whether the suction ring is aligned with the eye based on the detected light.