HK1221519B - Method and system for determining an eyeglass prescription - Google Patents

Description

Method and system for determining an eyeglass prescription

Technical Field

The present disclosure relates to systems and methods for determining an eyeglass prescription, particularly for a visual aid.

Background

Ametropic human eyes have refractive errors that can be described in terms of spherical, cylindrical, and axial orientations in a first approximation. This is based on the following assumptions: the visual defect can be approximately corrected by a lens having a simple surface such as a toroidal surface and a spherical surface. This approximation is sufficient to correct refractive errors of the light rays entering the center of the pupil of the eye.

Although the refractive error of the human eye is usually determined by relying on the subjective refraction of the patient being examined when presenting a plurality of optotypes to the patient by means of lenses having different refractive powers, so-called subjective refraction or dominant refraction, the possibility of measuring the refractive error of the eye has been available (available) for many years (objective refraction). Furthermore, it is possible to measure the optical power of the eye over the entire pupil and thus in particular also in the peripheral region of the pupil. Measurable errors include, for example, spherical aberration, coma, trefoil error (trefoil error), high order spherical aberration, and the like. In some embodiments, the objective refractive method is based on determining the wavefront of a propagating light beam. The functional principle of a wave front refractometer is described in document US6382795B1, which is incorporated herein by reference and whose feature protection can be sought, and also includes a summary of a number of different variants.

The refractive or imaging error of the human eye can be described mathematically by means of so-called Zernike polynomials. The error of the eye about sphere, cylinder and axis near the center of the pupil can be described, for example, by a second order Zernike polynomial. Therefore, these errors are often referred to as second order errors. The error away from the center can be described by higher order Zernike polynomials. Therefore, these errors are often referred to as higher order errors. The information obtained from the wavefront refractometer can be used in the formation of an improved typoscope or an improved vision correction method. A well-known example of a vision correction method is the process of wavefront-guided refractive surgery. In this process, a volume of any desired geometry is subtracted from the surface of the cornea to correct refractive errors, including those of higher order. Typically, to determine a lens prescription for a visual aid, an eye care professional determines a number of parameters. For example, in the case of ophthalmic lenses, the most relevant parameters are: the refractive index is generally given in the form of a sphere, cylinder and axis; assembly parameters such as pupil distance, assembly height, panoramic angle, etc.; and for example a near vision addition (near vision addition) in the case of progressive lenses. For contact lenses, the set of parameters typically includes at least a refractive value, similar to an ophthalmic lens, and a corneal curvature.

Conventionally, the determination of refractive value involves the use of subjective refractive techniques. Typically, this is performed by establishing a first set of (sphere, cylinder, axis) values as a starting point for the optimization. For example, the starting point may be provided, for example, by retinoscopy (autorefractometer measurement) by means of measurement of the currently worn ophthalmic lens, or other methods. An iterative optimization process is then started in which different refractive corrections, i.e. sets of (sphere, cylinder, axis) values, are provided to the patient until he/she reaches a visual acuity maximum on the eye chart. An example for determining the subjective refraction of an eye is provided in document US8226238B2, which is incorporated herein by reference and whose feature protection can be sought.

While newer and advanced objective refractive techniques are available, they have not achieved widespread adoption because many eye care professionals are reluctant to change from a proven and trusted subjective refraction.

Furthermore, it has been found that current methods for providing objective refractive techniques result in lens prescriptions that deviate from those obtained for the same eye by subjective refractive techniques. Of course, providing a lens prescription determined by objective refractive techniques that does not comply with lens prescriptions obtained via subjective refractive techniques is undesirable and therefore may not be considered optimal by the patient.

Disclosure of Invention

It is therefore an object of the present invention to provide a system and method for determining an ophthalmic lens prescription for a patient's eye in an automated manner or via an objective refractive technique that more closely complies with ophthalmic lens prescriptions obtained via subjective refractive techniques.

Thus, according to a first aspect of the present invention, there is provided a method for determining an eyeglass prescription for an eye, in particular by using a non-transitory computer readable medium, the method comprising the steps of: providing a measurement indicative of a refractive property of the eye, in particular a wavefront or a measurement representative of a wavefront; establishing an optimization space corresponding to a plurality of possible eyeglass prescriptions for the eye; determining a merit function, wherein the value of the merit function corresponds to the visual function of the eye when corrected using one of the plurality of possible lens prescriptions within the optimization space, wherein the merit function comprises a term that depends on the magnitude of the corrective astigmatism of the one of the plurality of possible lens prescriptions and that results in a value of the merit function that is less optimal the higher the magnitude of the corrective astigmatism and/or the higher the magnitude of the difference between the corrective astigmatism and the subjective corrective astigmatism; and determining the eyeglass prescription by optimizing the value of the merit function.

It has been found that the present method for determining an eyeglass prescription from wavefront aberrations using objective refraction systematically estimates, on average, higher magnitude astigmatism corrections compared to subjective refraction of the same eye. It has been found that this indicates a systematic error in the objective measures (metrics) used to determine the best prescription. Thus, the merit function includes a term that depends on the magnitude of the corrective astigmatism of one of the plurality of possible lens prescriptions and results in the value of the merit function being less than optimal the higher the magnitude of the corrective astigmatism. Alternatively or additionally, the merit function includes a term that depends on the magnitude of the corrective astigmatism of one of the plurality of possible lens prescriptions and that results in the value of the merit function being less than optimal the higher the magnitude of the difference between the corrective astigmatism and the subjective corrective astigmatism. The subjectively corrected astigmatism may be provided by subjective refraction, in particular by known subjective refraction techniques, in particular via earlier measurements. Alternatively, the subjective refraction can also be provided as a numerical value, in particular a fixed numerical value, in particular as a data set.

The term "merit function" is well known to those skilled in the art. The merit function (also referred to as a figure of merit function) is a function that measures the agreement between the best and fitted model (here, the apparent function) for a particular selection of parameters. In other words, the merit function evaluates the parameter selection by providing a value, i.e., the value of the merit function. The merit function may become smaller as it approaches the optimum. However, it can also be designed in such a way that it becomes larger for a better choice of parameters. During optimization, the parameters are adjusted based on the value of the merit function until an optimal value (maximum or minimum) is obtained, thus producing a best fit or optimal value with the corresponding parameter given the optimal value of the merit function.

It is therefore proposed to add to the metric or merit function a term which penalizes (punish) a potential or possible lens prescription based on its magnitude of corrected astigmatism, expressed for example by the "cyl" value of the lens prescription. Thus, as will be explained in more detail below, such a modified measure will not only result in a solution with less astigmatism to be preferred in the case of two solutions providing the same optimal value for visual function, but it will also result in a statistically specified smaller astigmatism value. The present invention therefore takes into account the negative effects of distortion due to the patient perceived corrective astigmatism of the optimal prescription.

The basic idea of the invention is therefore to add a term that penalizes a metric based on the magnitude of the corrected astigmatism.

The step of providing a measurement indicative of a refractive property of the eye may in practice be carried out, for example, by wavefront measurement using a wavefront aberrometer. However, the step of providing a measurement indicative of a refractive property of the eye may also be carried out simply by providing a data set indicative of a refractive property of the eye. The data set may then have been previously obtained, in particular at another location, or may have been manually set to represent the refractive properties of a real or fictitious eye.

According to a second aspect of the invention, there is provided a method for manufacturing a viewing aid, the method comprising the steps of: providing a measurement indicative of a refractive property of the eye, in particular a wavefront or a measurement representative of a wavefront; establishing an optimization space corresponding to a plurality of possible eyeglass prescriptions for the eye; determining a merit function, wherein the value of the merit function corresponds to the visual function of the eye when corrected using one of the plurality of possible lens prescriptions within the optimization space, wherein the merit function comprises a term that depends on the magnitude of the corrective astigmatism of the one of the plurality of possible lens prescriptions and that results in a value of the merit function that is less optimal the higher the magnitude of the corrective astigmatism and/or the higher the magnitude of the difference between the corrective astigmatism and the subjective corrective astigmatism; and determining a lens prescription by optimizing the value of the merit function and manufacturing a vision aid from the lens prescription.

According to a third aspect of the present invention there is provided a system for determining an eyeglass prescription for an eye comprising: a processing unit configured to receive information about the measured wavefront from the wavefront aberrometer, establish an optimization space corresponding to a plurality of lens prescriptions for the eye, determine a merit function, wherein a value of the merit function corresponds to a visual function of the eye when corrected with one of a plurality of possible lens prescriptions within the optimization space, wherein the merit function comprises a term that depends on a magnitude of a corrective astigmatism of the possible lens prescriptions and that results in a value of the merit function being less optimal the higher the magnitude of the corrective astigmatism and/or the higher the magnitude of the difference between the corrective astigmatism and the subjective corrective astigmatism, and determine the lens prescription by optimizing the value of the merit function.

According to a fourth aspect of the present invention, there is provided, in particular by making use of a non-transitory computer readable medium, a computer program product, in particular non-transitory, comprising program code means for performing the steps of a method for determining an ophthalmic lens prescription, in particular when the computer program product is run on a computer, the method comprising the steps of: providing a measurement indicative of a refractive property of the eye, in particular a wavefront or a measurement representative of a wavefront; establishing an optimization space corresponding to a plurality of possible eyeglass prescriptions for the eye; determining a merit function, wherein the value of the merit function corresponds to the visual function of the eye when corrected using one of the plurality of possible lens prescriptions within the optimization space, wherein the merit function comprises a term that depends on the magnitude of the corrective astigmatism of the one of the plurality of possible lens prescriptions and that results in a value of the merit function that is less optimal the higher the magnitude of the corrective astigmatism and/or the higher the magnitude of the difference between the corrective astigmatism and the subjective corrective astigmatism; and determining the eyeglass prescription by optimizing the value of the merit function.

The method according to the second aspect of the invention, the system according to the third aspect of the invention and the computer program product according to the fourth aspect of the invention provide the same advantages as the method according to the first aspect of the invention.

In a refinement of the method according to the first aspect, establishing the optimization space comprises defining a range of one or more parameters characterizing the prescription.

Thus, as a result of the optimization process, the parameters characterizing the ophthalmic prescription can be directly obtained as a result of the optimization process.

In another refinement, the one or more parameters characterizing the ophthalmic lens prescription include one or more parameters selected from the group consisting of sphere, cylinder, axis, M, J₀And J₄₅Selected from the group of (1). In particular, the parameter may be spherical, cylindrical and axial, or may be M, J₀And J₄₅。

Of course, additional parameters may be possible, such as a second order Zernike polynomial. For example, establishing an optimization space may include defining ranges for one or more parameters characterizing a prescription.

The optimization space can be a single space, such as, for example, a space having three or more dimensions. The three or more dimensions can include spherical, cylindrical, and axial or M, J₀And J₄₅. In some embodiments, the optimization space includes two or more subspaces. One of the subspaces can include dimensions for a sphere. Another of the subspaces can include a dimension for a cylinder and a dimension for an axis. In some embodiments, one of the subspaces can include a dimension for M, while another of the subspaces includes a dimension for J₀And for J₄₅Of (c) is calculated.

Regardless of whether the parameters can be set to spherical, cylindrical and axial or M, J₀、J₄₅Or may even be set to second order Zernike coefficients, may depend on the apparent function used to determine the merit function or any other preference. All parameters or parameter combinations may be utilized equally. As those skilled in the art will readily appreciate, the set of parameters comprising sphere, cylinder and axis can be recalculated to provide M, J₀And J₄₅The parameter set of (1):

where α designates the axis, cyl designates astigmatic power in diopters and sph designates spherical power in diopters₀And J₄₅To determine the cylinder and axis components:

further, the second order Zernike coefficients are calculated using the following equationAndcan be used as a parameter set. However, even these Zrenike coefficients can be derived from parameter set M, J using the following equations₀And J₄₅Is obtained in which r_PIs the radius of the pupil:

in a further refinement, optimizing the value of the merit function includes iteratively determining a correction wavefront indicative of the refractive properties of the eye and a corresponding possible eyeglass prescription.

Thus, a correction wavefront is determined based on each possible lens prescription. Based on the corrected wavefront, the corresponding value of the merit function is calculated. The value of the merit function depends on which visual function of the eye is used to construct the merit function and provide the corresponding value of the merit function.

Different kinds of optimization metrics and merit functions for providing the results of objective refractive techniques have been conceived and are well known to those skilled in the art. For example, the contents of each of the documents US7857451B2 "System and Method for optimizing the clinical optical descriptions", US2012/0069297a1 "eyeglass description Method", US2005/0110946a1 "Objective management recovery", WO03/092485a1 "imaging Method for vision quality", US2008/0100800a1 "eyeglass description Method", US2009/0015787a1 "Apparatus and Method for determining an eyeglass description for a vision layer" and US8205987B2 "Method for optimizing the visual components for the vision layer" may be referred to and protected by the disclosure of each of these documents, and the contents of each of these documents may be referred to and referred to by the disclosure of each of these documents, and the disclosure of each of these documents may be made in combination with the features of each of these documents. In case of conflict, the present specification will control.

In a further refinement, the lens prescription is determined by optimizing the value of the merit function to a maximum value, and wherein it is determined that the higher the magnitude of the corrective astigmatism of one of the plurality of possible lens prescriptions, the smaller the value.

Alternatively, the lens prescription is generated by optimizing the value of the merit function to a minimum value, and wherein the higher the magnitude of the corrective astigmatism of one of the plurality of possible lens prescriptions, the greater the value of this term.

The optimum may be a minimum or a maximum depending on the merit function and depending on the apparent function that the merit function is describing. Accordingly, this term must induce the opposite direction in order to "penalize" the optimization process for utilizing corrected astigmatism with a high magnitude. Thus, in the case of finding the maximum, if the astigmatism magnitude is high, the term must be smaller (or more negative). Further, in the case of finding the minimum, if the magnitude of the correction astigmatism is high, the term must become large (or more positive).

In a further development of the method according to the first aspect, the visual function is expressed in units, which are diopters.

In this way, the magnitude of the astigmatism can be directly implemented into the merit function in a uniform manner. For example, the magnitude of astigmatism can be expressed as the cylindrical component (cyl) of the eyeglass prescription and thus the unit is diopters. Therefore, it would be most consistent if the merit function would also be equal to the value in diopters.

In a further development of the method according to the first aspect of the invention, the visual function, when corrected, is a sensitivity value of the eye.

Alternatively, for example, the visual function may be a blur value of the eye when corrected.

Possible merit functions for visual function using image sensitivity values or blur values are suggested, for example, in the literature as provided above, and are incorporated herein by reference, and feature protection thereof may be sought. Such merit functions without the additions suggested by the present invention are therefore generally known to those skilled in the art.

Further, both the sensitivity value and the blur value are expressed in diopters as units thereof. Thus, the magnitude of astigmatism can be directly implemented into the merit function.

In a further refinement of the method according to the first aspect of the invention, the term is proportional to the magnitude of the correction astigmatism.

Thereby, a simple implementation of correcting the magnitude of astigmatism into a merit function may be provided. For example, the proportionality constant may be adjusted by comparing the results of a predicted eyeglass prescription determined via an objective refraction technique with objective refraction techniques for a large set of tested eyes. Examples of this are given further in the following disclosure.

In another example, the term may have the form C-MOA, where MOA is the magnitude of the corrected astigmatism for one of a plurality of possible eyeglass prescriptions in diopters, and C is a proportionality constant of +0.15 or-0.15.

It has been found that this implementation of this term results in a simple and consistent merit function that empirically fully complies with the results of subjective refraction techniques.

In a further refinement, the term can also have the form:

wherein MOA is the magnitude of the corrective astigmatism of one of the plurality of possible eyeglass prescriptions, n is an order constant, and C_iAre coefficients of each order. By such a polynomial, even more complex forms of terms or objective refractive outcome deviations can be implemented into the merit function, thereby providing the patient or wearer with an empirical method for influencing the outcome developed by the objective refractive technique for finding the most appropriate lens prescription.

In another alternative, the term may have the form:

±C·e^MOA

where MOA is the magnitude of the corrective astigmatism for one of the plurality of possible eyeglass prescriptions, e is a mathematical constant e, and C is a scaling factor.

Thus, the magnitude of astigmatism can be penalized in a more rigid, ultra-protective manner, and based on statistical analysis can provide a suitable method of correction that takes into account the inconveniences considered by the wearer.

In a further development of the method, a measurement of the wavefront indicative of the refractive properties of the eye is provided by a measurement with a wavefront aberrometer.

For example, the wavefront aberrometer may be a Hartmann-shack sensor, a Chernen (Tschening) aberrometer, a Talbot aberrometer, or a dual-pass aberrometer.

In a further development of the method according to the first aspect of the invention, the method further comprises the step of outputting an eyeglass prescription.

The output device may include an electronic display or a printer. However, the outputting step may also be carried out by storing the eyeglass prescription on a storage device, in particular a non-transitory storage device, or by transmitting the eyeglass prescription to the manufacturing location via a data network.

In a further development of the method, the step of providing a measurement of the wavefront is carried out at a first location, and wherein the steps of establishing an optimization space, determining a merit function and determining a lens prescription from the value of the merit function are carried out at a second location remote from the first location, and wherein the provided measurement is transmitted from the first location to the second location via a data network.

Thus, a relatively high amount of computing power may be provided to numerous eyeglass stores, ophthalmologists, and the like. The advantages of the proposed method can thus be more easily provided to all wearers. The wavefront aberration data provided via the aberrometer can be sent to a computing or processing unit via a data network. Here, calculation of the optimum eyeglass prescription can be performed. The results of the determined eyeglass prescription can then be sent back to the location where the aberrometer is positioned. Alternatively, the data may also be sent to a third entity or location that produces the final ophthalmic lens. Of course, the ophthalmic lens can also be manufactured at the second position of the calculation unit or at the first position of the aberrometer.

In a further refinement of the system according to the third aspect of the invention, the system further comprises a wavefront aberrometer configured to measure a wavefront indicative of a refractive property of the eye. Again, the wavefront aberrometer may be a hartmann-shack sensor, a cherning aberrometer, a talbot aberrometer, or a dual-pass aberrometer.

In a further refinement, the wavefront aberrometer is located at a first location, wherein the processing unit is located at a second location, and wherein the first location and the second location are connected via a data network.

As demonstrated above, this may enable a single processing unit to serve numerous eyeglass stores each having a wavefront aberrometer. Thus, a single second location at which the processing unit is located may be connected to a multitude of first locations via a data network. This avoids the necessary computing power being located directly at each first location or at the glasses shop, for example.

In another refinement, the system includes an output device configured to output the determined eyeglass prescription.

As already demonstrated above, the output device may be an electronic display or a printer. Further, the output device may be a storage medium storing an eyeglass prescription.

It goes without saying that the features mentioned above and the following features can be used not only in the combination provided but also in different combinations or individually without departing from the scope of the invention.

Drawings

Other features and advantages of the present invention will be apparent from the detailed description that follows. Unless defined otherwise, all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the drawings:

FIG. 1 illustrates one embodiment of a method for determining an eyeglass prescription for an eye;

FIG. 2 illustrates one embodiment of a method for manufacturing a viewing aid;

FIG. 3 shows a chart explaining the advantages of the present invention;

FIG. 4 shows another graph explaining the advantages of the present invention;

FIG. 5 illustrates one embodiment of a system;

FIG. 6 illustrates another embodiment of a system; and

fig. 7 shows another embodiment of the system.

Detailed Description

Referring to FIG. 1, one embodiment of a method 100 generally includes a number of steps, as shown in a flow chart. In a first step 110, the optical phase error of the patient's eye is measured using an objective method. Typically, this involves measuring the wavefront reflected from the eye using a suitable sensor. Examples of sensors include various wavefront aberrometers, such as Hartmann-Shack wavefront sensors, Chechering aberrometers, Talbot aberrometers, and double-pass aberrometers. The functional principle of a wavefront aberrometer is described in DE60121123T2, which also includes a summary of a number of different variants.

The measurement data is used as input to a processing unit, which typically comprises an electronic processor (e.g. a computer). The processing unit establishes a multi-dimensional optimization space (step 120) for which the processing unit calculates a merit function corresponding to, for example, the visual acuity of the eye. The dimensions of the optimization space typically correspond to the sphero-cylindrical corrections characterizing the ophthalmic prescription (e.g., sphere, cylinder, and axis). The range of each dimension of the optimization space may be set by the eye care professional or preset by the processing unit. For example, the algorithm used to establish the optimization space can default within a certain range of each dimension, or the default can be rejected by the eye care professional based on the professional experience with the patient. The values of the sphero-cylindrical correction in each range may be established as desired. For example, each dimension may include a number of preset numbers of values (e.g., 10 or more, 100 or more), so incremental changes between values are determined by range. Alternatively, or in addition, incremental changes between values may be preset, in which case the number of values per dimension is determined by setting a range. In some embodiments, the values may correspond to stock lens (stock lens) values within a range in each dimension.

As an example, an optimization space can be established based on a patient's pre-existing prescription, where the range for sphere and cylinder is set to-5 diopters to +5 diopters near the sphere and cylinder values of the pre-existing prescription. For example, within each range, these values may be incremented by 0.25 diopters.

Typically, the result is an optimization space consisting of a finite number of (sphere, cylinder, axis) or (mean power ('M'), J₀，J₄₅) Coordinate composition for which the merit function may be evaluated.

In some embodiments, the optimization space consists of a single space. For example, each point in the optimization space may be three component vectors, e.g., having components corresponding to a sphere, cylinder, and axis, or alternatively, a Jackson cylinder (M, J)₀，J₄₅) The component (c). In a particular embodiment, the optimization space is divided into a plurality of optimization subspaces, e.g., two optimization subspaces. For example, each point in the first subspace may be a value for sphere correction or defocus, while the component of the midpoint in the second subspace may be a component for cylinder and axis or Jackson's cylinder (J)₀，J₄₅) The value of (c). In a third step, in either case, a surface representing the wavefront for optical correction for each coordinate in the optimization space or subspace is created and subtracted from the original wavefront, which produces a series of corrected wavefronts (step 130).

Then, in step 4, a merit function is calculated for each of those wavefronts (step 140), which is associated with visual acuity, contrast sensitivity, or with another measure thereof of visual efficacy, or with a combination of those measures of visual efficacy.

In general, when the optimization space is divided into more than one subspace, the correction of the first subspace (e.g., sphere) should be determined first, and then subtracted from the measured wavefront before determining the correction of the second subspace (e.g., cylinder and axis).

To calculate data for each point in the optimization space, a corresponding correction wavefront is calculated. The corrected wavefront is the measured wavefront corrected by the corresponding spherical correction value. In particular, in particular embodiments, the sphere (referred to herein as a sphere correction value) is increased depending on the point in the optimization space. The shape of such a sphere at any radial position, i.e. r in millimeters, is given by the following equation:

wherein r is₀Is the pupil radius in millimeters and

where D is a point in sphere power (sphere power) optimization subspace in diopters.

Then, a merit function value for each of the generated correction wavefronts is calculated. In general, the merit function values may be calculated in a variety of ways. In certain exemplary embodiments, the merit function may be calculated according to the METHOD disclosed in U.S. patent application Ser. No. 11/840,688, entitled "APPATUS AND METHOD FOR DETERMINING AN EYEGLASSPRESCRIPTION FOR A VISION DEFECT OF AN EYE," filed on 8, 17.2007, which is hereby incorporated by reference in its entirety AND whose feature protection may be sought.

For example, in some embodiments, at least two sub-metrics can be determined for one of the sets of parameters in different stages of light propagation through the optical system represented by the eye and the optical component corresponding to the eyeglass prescription. In other words, the light passes through the optical system represented by the eye and the optical component. Now, consider the deviation of a ray from the ideal when it has passed through (propagated through) the system represented by the eye and by the correction of different travel distances, as expressed by a quality metric (sub-metric). Propagation in the opposite direction, e.g. directed towards the object from the system represented by the eye and the optical component, is likewise conceivable. The propagation considered here is not with a fixed direction through the system represented by the eyes and the correction, but can be implemented for any desired number of directions (e.g. in the general direction of the line of sight).

For example, these sub-metrics can include a light quality metric, such as a metric that measures the energy of a Strehl ratio (Strehl ratio) or a point image wash-out (washout) function included in an Airy disc (Airy disc).

An overall metric, in particular reflecting the quality of caustic ("caustic metric"), can be determined from the weighted sum of the previously determined sub-metrics. In some embodiments, all sub-metrics are given equal weight in the determination of the total metric (the caustic metric). In particular embodiments, the sub-metrics of a preferred propagation phase are weighted more heavily than the sub-metrics in the propagation phases before and/or after this preferred propagation phase. If sub-metrics are used that, for example, take into account the image quality of different planes, the sub-metrics of the image on the retina (which correspond to the sub-metrics in the preferred propagation phase) will preferably be given more weight than the sub-metrics of the image before or after the retina of the eye. The weight ratio may be, for example, 60/40. A detailed description of an example of such a possible metric is given in document US2010/0039614a1, the disclosure of which is incorporated herein by reference and whose feature protection can be sought.

According to the invention, the merit function comprises a term that takes into account the magnitude of the correction astigmatism found in the optimized solution of the lens prescription. Thus, this so-called "penalty term" results in that the higher the magnitude of the possible prescription and/or the higher the magnitude of the difference between the corrected astigmatism and the subjectively corrected astigmatism provided by the subjective refraction, the less optimal the outcome of the visual function. The subjective corrective prescription including the subjective corrective astigmatism may be provided as a fixed number or may have been measured via an earlier subjective refraction technique. Thus, a solution with a lower magnitude of astigmatism or a lower magnitude of deviation from subjectively corrected astigmatism would be preferred. For example, visual function may be effectively blurred and such visual function may become minimized during optimization. This term can then be set to be proportional to the magnitude of the corrected astigmatism. Thus, as will be shown in more detail below, this term may be +0.15 times the magnitude of astigmatism of a possible lens prescription. All units are diopters and a lower astigmatism solution would therefore be preferred.

As an example, it may be assumed that the merit function is the squared refractive difference between the paraxial curvature of the measured wavefront and the objective prescription. Considering only Zernike aberrations through the fourth order, such merit function may be given by:

whereinIs the Zernike coefficient, r is the pupil radius, and m, j₀And j₄₅Is a trial refraction single component. In this case, the optimal refraction single component M, J₀、J₄₅Are those that minimize the merit function and are given by:

as an example of a modified merit function, namely metric', penalizing the magnitude of astigmatism, in particular the deviation of the objective cyl from that obtained by subjective refraction would be

metric′＝metric+k((j₀-J₀)²+(j₄₅-J₄₅)²)。

Wherein J₀And J₄₅Is the cyl component of the subjective refraction and k is a constant that controls the magnitude of the penalty. Maximizing the new metric of cyl component J'₀And J'₄₅Simply given by:

it should be noted that for this simple metric, the final cyl component is simply a weighted average of the component found with the metric and the component from the subjective refraction.

As a numerical example, one may assume that a patient with a pupil diameter of 4mm has-2 diopters of cyl at 0 degrees (negative cyl agreement) and +1 diopter of sphere, or equivalently, M ═ 1.00, J₀1.00 and J₄₅The measurement of the prescription of 0. Further, in the present invention,and all other Zernike coefficients are equal to 0. Using the metric to combine theseNumber input to M, J₀And J₄₅Is 1.00, J₀1.25 and J₄₅0. M ' is given 1.00, J ' using the result of the modified metric with k 0.5 '₀＝1.17、J′₄₅＝0。

In this simple example, the modified metric pushes the objectively derived cyl closer to the desired subjectively specified cyl. For more complex merit functions and eye aberrations, the additional cyl penalties may also be systematically scaled down away from the specified local optimum of cyl, allowing the algorithm to locate the local optimum closest to the subjective result.

Finally, in step 160, the eyeglass prescription is determined as a result of the optimization process.

Fig. 2 illustrates one embodiment of a method 200 of manufacture. This manufacturing method may start in a start step 205. The method 100 of determining a corresponding eyeglass prescription can then be implemented. Then, in step 170, a vision aid, such as an ophthalmic lens, may be manufactured. The method then ends in step 210.

Alternatively, after the lens prescription is determined in step 100, the lens prescription may be output in step 180. The output may be on an electronic display, through a printer, or may be an output storage device that stores the eyeglass prescription. The method then ends in step 215.

In fig. 3, graph 220 shows the distribution of the difference between the calculated astigmatism and the astigmatism prescribed by the subjective refraction for just over 9000 eyes. The "no term" curve represents the difference with a known metric, while the "with term" curve shows the distribution after proportionally adding a so-called "rubber band" penalty based on the magnitude of the astigmatism. In this data set, all eyes whose prescribed astigmatism is exactly zero (about 10% of the original set) are removed, as they will bias the results.

The penalty term is set to 0.15 times the magnitude of the astigmatism. In other words, rather than minimizing the effective blur, the blur estimate plus 0.15 times the estimated astigmatism are in diopters. Therefore, a lower astigmatism solution is advantageous.

The median difference from the conventional measure of the data set, which has a higher astigmatism value than the subjective refraction, is 0.11 diopters. With the modified metric, the median difference is eliminated; to 0.00. At the same time, the width of the distribution is not significantly affected by the offset. For the conventional metric, the 25 to 75 percent difference is-0.059 to 0.301 diopters for a width of 0.360, while for the modified metric, the range is more symmetric-0.168 to 0.178 for a width of 0.348 diopters.

In fig. 4, the before and after curves for the magnitude of the astigmatism difference (versus the difference in cyl magnitude) are shown. Here, the distribution of the modified metrics is slightly narrower. For eyes whose cyl is shifted more than 0.01 diopters, eyes shifted closer to the subjective refraction prescription outnumber those shifted further away by a ratio of about 2: 1.

Fig. 5 shows an embodiment of the system 10 according to the invention. The system 10 for determining a lens prescription for an eye comprises a processing unit 14 configured to receive information about measurements indicative of a refractive property of the eye, establish an optimization space corresponding to a plurality of lens prescriptions for the eye, determine a merit function, wherein a value of the merit function corresponds to a visual function of the eye when corrected with one of a plurality of possible lens prescriptions within the optimization space, wherein the merit function comprises a term that depends on a magnitude of a corrective astigmatism of said possible lens prescription and results in a higher magnitude of the corrective astigmatism, the less optimal the value of the merit function, and determine the lens prescription by optimizing the value of the merit function.

Fig. 6 shows another embodiment of the system 10 according to the invention. The optical wavefront aberration of a patient's eye having a wavefront aberration can be determined by the aberrometer 12. Further, the subjective refraction may also be determinable. The calculation of the eyeglass prescription is then carried out on the processing unit 14. The processing unit 14 may comprise a computer program product 15 storing executable program code to perform the method explained above. The system 10 may then further include an output device 16, which may be a display, a printer, or a storage device that outputs the determined eyeglass prescription to the output device 16. The aberrometer 12 is connected to the processing unit 14 via a line 18. The processing unit 14 is connected to the output device 16 via a line 20. Lines 18 and 20 are each a wired or wireless connection for data transfer between the processing unit 14 from or to the aberrometer 12 and the output device 16.

Thus, the system 10 is able to automatically determine an eyeglass prescription based on data provided via the aberrometer. However, instead of the aberrometer 12, data which is the basis for the optimization procedure may also be obtained via line 18 from a storage device which stores a plurality of patient data obtained in advance.

In fig. 7, another embodiment of the system 10' is shown. The aberrometer 12 may be located at a first position 26. The processing unit 14 is located at a second location 28. The output device 16 may be located at the third location 30 or may also be located at the first location 26. Further, a manufacturing unit 32 from the manufacturing of the viewing aid may be present at the third location 30 or the first location 26.

The first, second and third positions 26, 28, 30 are remote from one another. The first location 26 is connected to the second location 28 via the data network 22. The second location 28 and the third location 30 are connected via the data network 24. Thereby, it may be possible that refractive data provided via the aberrometer 12 can be sent to the processing unit 14. Further, the subjective refraction, in particular the subjective correction astigmatism, may also be sent to the processing unit 14, e.g. from the first location 26 or any other location. Further, for example, the determined eyeglass prescription may then be sent back to a first location, such as an eyeglass store, for identification by an ophthalmic professional and provided to a potential wearer, for example. Further, the determined eyeglass prescription may also be forwarded to a remote manufacturing unit for manufacturing a corresponding vision aid. The manufacturing unit may also be located at the first location 26. In this case, the data of the aberrometer are transmitted via connection 22 to processing unit 14 at second location 28, and the calculated eyeglass prescription is then transmitted back to first location 26 and its possible manufacturing unit 32. Alternatively, from the second location 28, the determined eyeglass prescription may be transferred to a third location 30 having a possible manufacturing unit 32 to manufacture the viewing aid. Finally, it is possible that from this third location 30, the manufactured viewing aid is then shipped to the first location 26 as indicated by arrow 34.

Although the preceding discussion relates to implementations for correcting up to second order aberrations, in general, the invention is not limited to second order aberrations. For example, in some embodiments, the method may be extended to allow refraction using higher order aberrations. In such cases, the optimization space is extended by one or more additional dimensions, e.g., for higher order aberrations such as spherical aberration and/or coma. This higher order refraction can then be used by the eye care professional to specify an eye correction that includes higher order corrections by changing the phase of the incident wavefront in the plane of the pupil according to the specified higher order aberration correction.

Additionally, although the embodiments discussed above refer to a spectacle typoscope, in general, the techniques can be applied to determine contact lenses for what should be considered a "typoscope" or also an prescription for refractive surgery. Various embodiments have been described. Other embodiments are within the claims.

Claims (16)

1. A method (100) for determining an eyeglass prescription for an eye, the method comprising the steps of:

providing (110) a measurement indicative of a refractive property of the eye;

establishing (120) an optimization space corresponding to a plurality of possible eyeglass prescriptions for the eye;

determining (130,140) a merit function, wherein the value of the merit function corresponds to the visual function of the eye when corrected with one of a plurality of possible lens prescriptions within the optimization space, wherein the merit function comprises a term that depends on the magnitude of the corrective astigmatism of the one of the plurality of possible lens prescriptions and that results in a value of the merit function that is less optimal the higher the magnitude of the corrective astigmatism and/or the higher the magnitude of the difference between the corrective astigmatism and the subjective corrective astigmatism; and

determining (160) the eyeglass prescription by optimizing (150) the value of the merit function.

2. The method according to claim 1, wherein establishing (120) an optimization space comprises defining ranges of one or more parameters characterizing the ophthalmic prescription.

3. The method according to claim 1 or 2, wherein optimizing (150) the value of the merit function comprises iteratively determining a correction wavefront indicative of the refractive properties of the eye and the corresponding possible lens prescription.

4. Method according to claim 1 or 2, wherein the lens prescription is determined by optimizing the value of the merit function to a maximum value, and wherein the higher the magnitude of the corrective astigmatism of one of the plurality of possible lens prescriptions, the smaller the value of this term, or the lower the value of the corrective astigmatism of one of the plurality of possible lens prescriptions, and wherein the higher the magnitude of the corrective astigmatism of this term, the larger the value of this term.

5. The method according to claim 1 or 2, wherein the visual function is a acuity value of the eye when corrected or a blur value of the eye when corrected.

6. A method according to claim 1 or 2, wherein said term is proportional to the magnitude of said corrected astigmatism.

7. A method according to claim 1 or 2, wherein the term is of the form:

wherein MOA is the magnitude of the corrective astigmatism of one of the plurality of possible ophthalmic lens prescriptions, n is an order constant, and C_iAre coefficients of each order.

8. A method according to claim 1 or 2, wherein the term is of the form:

±C·e^MOA

wherein MOA is a magnitude of corrective astigmatism for one of the plurality of possible lens prescriptions, e is a mathematical constant e, and C is a scaling factor.

9. The method according to claim 1 or 2, further comprising the step of outputting (180) the eyeglass prescription.

10. The method according to claim 1 or 2, wherein the step of providing (110) a measurement is carried out at a first location (26), and wherein the steps of establishing (120) an optimization space, determining (140) a merit function, and determining (160) the lens prescription by optimizing the value of the merit function are carried out at a second location (28) remote from the first location (26), and wherein the provided measurement is transmitted from the first location (26) to the second location (28) via a data network.

11. The method of claim 1, wherein the method is performed by utilizing a non-transitory computer readable medium.

12. A method (200) for manufacturing a visual aid, the method comprising the steps of:

determining (100) an eyeglass prescription according to the method of any of claims 1-11; and

manufacturing (170) the visual aid according to the lens prescription.

13. A system (10) for determining an eyeglass prescription for an eye, comprising a processing unit (14), the processing unit is configured to receive information about measurements indicative of refractive characteristics of the eye, establish an optimization space corresponding to a plurality of eyeglass prescriptions for the eye, determine a merit function, wherein the value of the merit function corresponds to the eye's visual function when corrected with one of a plurality of possible eyeglass prescriptions within the optimization space, wherein the merit function includes a term that depends on the magnitude of the corrective astigmatism of the possible lens prescription, and results in a higher magnitude of the corrected astigmatism and/or a higher magnitude of the difference between the corrected astigmatism and the subjectively corrected astigmatism, the less optimal the value of the merit function, and determining the eyeglass prescription by optimizing the value of the merit function.

14. The system according to claim 13, wherein the wavefront aberrometer (12) is located at a first location (26), wherein the processing unit (14) is located at a second location (28), and wherein the first location (26) and the second location (28) are connected via a data network (22).

15. The system according to claim 13 or 14, wherein the system (10) further comprises an output device (16) configured to output the determined eyeglass prescription.

16. A non-transitory computer-readable medium having stored thereon program code that, when executed, causes a computer to perform the method according to one of claims 1 to 10.