Ophthalmic lens and method for customizing defocus in myopia control

Abstract

Computer-implemented method for customizing defocus for designing an ophthalmic lens (18, 19) for myopia control for the purposes of using the design for the production of an ophthalmic lens (18, 19) According to the method, an accommodative eye model (11) is provided, comprising at least one input eye parameter and at least one accommodation adjustment, wherein the accommodative eye model (11) outputs a distance-viewing focal plane (8) and a near-viewing focal plane (9). A defocus model is provided, wherein a defocus magnitude is defined based on a difference between the distance-viewing focal plane (8) and the near-viewing focal plane (9). A defocus magnitude (25) of a patient is derived, wherein at least one individual eye parameter of the patient is provided as input (22), wherein the patient is of an age group. An ideal age-specific defocus magnitude (24) is derived, wherein at least one ideal eye parameter specific to the patient's age group is provided as input (22). A compensation basic magnitude (26) is derived based on a difference between the defocus magnitude (25) of the patient and the ideal age-specific defocus magnitude (24).

Description

CZVG033PW00228.08.2025 / USOphthalmic lens and method for customizing defocus in myopia control

[0001] The invention relates to a product comprising an ophthalmic lens for myopia control and a computer-implemented method for customizing defocus for designing an ophthalmic lens for myopia control for the purposes of using the design for the production of an ophthalmic lens for myopia control.

[0002] Myopia correction with a single-vision lens may result in peripheral hyperopic defocus while the central retina is in focus. As eye growth is regulated by the peripheral retina, peripheral hyperopic defocus may cause the eyeball to grow longer along the optical axis, increasing the degree of myopia. Ophthalmic lenses with peripheral myopic defocus are used for the purpose of slowing down the axial growth of the eyeball in children as a means of controlling myopia progression.

[0003] Accommodation of the eye is the process of adapting the optical power of the eye to focus on an object in a given distance between the far point and the near point. To this end, the shape of the eye lens as well as the shape of the cornea are modified by a mechanism involving muscles and fibers in the eye.

[0004] From WO 2018 / 138140 A2 it is known to establish geometric and optical properties of an eye model which includes personalized refraction data.

[0005] From T. Liu, L.N. Thibos, "Customized models of ocular aberrations across the visual field during accommodation", Journal of Vision (2019) 19(9) :13, 1-24, an individual eye model is known which reproduces measurements of wavefront aberrations across the visual field at different accommodative states .

[0006] From CN114980800A, WO 2021 / 184452 Al it is known to capture a series of images at different focus positions and to find the optimal focus position, translating the focus position into a refraction determination.

[0007] From CN112068331A it is known to customize defocus lenses based on peripheral defocus obtained from 10 discrete retinal locations between 10 to 30° at four major meridians.

[0008] From CN202310359969 it is known to reconstruct a 3D defocus image plane based on corneal biometrics and the retinal shape for optimization of orthokeratology lens fitting.

[0009] From EP2628441A1, WO 2012 / 049343 it is known to extract the defocus from aberration data obtained by an open-view Hartmann-Shack wavefront sensor. A basic scanning protocol allows the estimation of refraction in a circular retinal patch of 50° diameter, or ±25° from central fixation, in 3 seconds.

[0010] It is the object of the present invention to provide a method for customizing peripheral defocus while accounting for accommodation, and an ophthalmic lens produced on the basis of the determined peripheral defocus.

[0011] A first aspect of the invention is a computer-implemented method for customizing defocus for designing an ophthalmic lens for myopia control for the purposes of using the design for the production of an ophthalmic lens for myopia control comprising the steps of: a) Providing an accommodative eye model comprising at least one input eye parameter and at least one accommodation adjustment, wherein the accommodative eye model outputs a distance-viewing focal plane and a near-viewing focal plane, wherein the distance-viewing focal plane is based on the at least one input eye parameter,wherein the near-viewing focal plane is based on the at least one input eye parameter and the at least one accommodation adjustment; b) Providing a defocus model based on the accommodative eye model, wherein a defocus magnitude is defined based on a difference between the distance-viewing focal plane of the accommodative eye model and the near-viewing focal plane of the accommodative eye model; c) Deriving a defocus magnitude of a patient based on the defocus model, wherein at least one individual eye parameter value of the patient is provided as the at least one input eye parameter of the accommodative eye model, wherein the patient is of an age group; d) Deriving an ideal age-specific defocus magnitude based on the defocus model, wherein at least one ideal eye parameter value specific to the patient's age group is provided as the at least one input eye parameter of the accommodative eye model; e) Deriving a compensation basic magnitude of the ophthalmic lens for myopia control based on a difference of the defocus magnitude of the patient from the ideal age-specific defocus magnitude, wherein the compensation basic magnitude (26) is proportional to the difference between the defocus magnitude (25) of the patient and the ideal age-specific defocus magnitude(24) .

[0012] First, some terms used in the context of the invention are defined.

[0013] The accommodative eye model may be a computational model of an eye with the purpose of simulating optical properties of the eye . It may comprise a representation of an optical system which approximates a human eye . To this end, the accommodative eye model may comprise structural and optical parameters of refractive surfaces . The parameters may be taken from biological literature disclosing parameters of normal human eyes .

[0014] An optical axis of the eye may be defined in the accommodative eye model . To determine optical properties of the accommodative eye model , ray tracing may be performed by modelling light transport through the eye model . This way, a retinal image may be simulated . It may also be possible to determine wavefront aberrations based on the accommodative eye model . Ray tracing may be performed computationally, for example by Zemax ray tracing .

[0015] The at least one input eye parameter of the accommodative eye model may be a structural parameter of the accommodative eye model . Preferably, it may be at least one of a corneal curvature , a central lens thickness , a curvature of an anterior lens surface and / or a curvature of a posterior lens surface . Further types of eye parameters may be the obj ect distance in mm, the corneal thickness in mm, the anterior corneal curvature in mm, the posterior corneal curvature in mm, the corneal refraction index, the aqueous humour in mm, the aqueous humour refraction index, the pupil si ze in mm, the radius of anterior lens surface in mm, the length of lens equatorial plane in mm, the radius of the posterior lens surface in mm, the lens volume in mm3, the lens refraction index, the vitreous chamber depth in mm, the vitreous refraction index, the axial length in mm and / or the overall refraction power in diopter .

[0016] The distance-viewing focal plane may be determined by ray tracing from a distant point through the accommodative eye model . To determine the distance-viewing focal plane , the fovea may be ensured to be always in focus . Additionally or alternatively, the Strehl ratio of a point spread function may be at a maximum . The ray tracing may comprise central and peripheral rays . Preferably, the ray tracing for determining the distance-viewing focal plane may comprise rays which are close to the optical axis of the eye . To determine the distanceviewing focal plane , the value of the input eye parameter of the accommodative eye model may be a value corresponding to the relaxed eye . Preferably, an accommodation adj ustment may not be applied .

[0017] The near-viewing focal plane may be determined by ray tracing from a near point through the accommodative eye model . To determine the near-viewing focal plane , the fovea may be ensured to be always in focus . Additionally or alternatively, the Strehl ratio of a point spread function may be at a maximum . To determine the near-viewing focal plane , the changes in the input eye parameters in near-viewing conditions for di fferent accommodation demands may be considered . To this end, the at least one accommodation adj ustment may be applied in the accommodative eye model to the at least one input eye parameter of the accommodative eye model . This way, the input eye parameter may be modi fied to reflect the changes due to an accommodation state of the eye . The accommodation adj ustment may be derived from the di f ference of the values of the input eye parameter between the relaxed eye and the eye in the accommodation state .

[0018] The accommodation adj ustment used in the accommodative eye model may be a function of an input eye parameter . It may be a ratio relative to the input eye parameter . The accommodation adj ustment may preferably be an accommodation adj ustmentof the corneal curvature , the central lens thickness , the curvature of an anterior lens surface and / or the curvature of a posterior lens surface .

[0019] The peripheral defocus increases from distance-viewing to near-viewing . In other words , it depends on the accommodation state of the eye . The inventors of the present invention have recogni zed that this can be used to define a defocus magnitude . A defocus magnitude may be defined as a di f ference between the distance-viewing focal plane and the near-viewing focal plane . The defocus magnitude may be calculated at di fferent distances from the optical axis of the eye .

[0020] By providing the individual eye parameter value of the patient , the defocus magnitude derived according to the invention has the advantage of being customi zed to the patient . By taking into account the accommodation adj ustment for determining the near-viewing focal plane , accommodation of the eye is taken into account .

[0021] In a defocus model provided according to the invention, the peripheral defocus magnitude may be obtained through optical simulation . Changes in lens geometry with accommodation and eye growth which may af fect the magnitude of peripheral defocus may be considered, particularly in the peripheral areas which may be blocked by the iris and contribute signi ficantly to peripheral defocus . Since the image plane is set by the optical power of the cornea and the lens together, the lens refraction may be included in the optical simulation . The cornea has been shown to undergo small changes with age , but to remain constant in refraction power for most subj ects throughout li fe , whereas lens power experiences an abrupt loss of compensatory changes at the onset of myopia .

[0022] The at least one individual eye parameter value of the patient provided as the at least one input eye parameter of the accommodative eye model , which is provided by the invention to derive the defocus magnitude of the patient , may be based on ocular biometrics of the patient . It may comprise a corneal curvature , a central lens thickness , a curvature of an anterior lens surface and / or a curvature of a posterior lens surface . The value of the individual eye parameter may be obtained from measuring the corresponding parameter of the patient ' s eye . The patient may have myopia . The patient ' s age group may be known to the day and / or to the month and / or to the year and / or to a period of 3 years . The patient may be a child or adolescent .

[0023] The at least one ideal eye parameter value speci fic to the patient ' s age group provided as the at least one input eye parameter to the accommodative eye model , which is provided by the invention to derive the ideal age-speci fic defocus magnitude , may be based on ocular biometrics . It may comprise a value of a corneal curvature , a central lens thickness , a curvature of an anterior lens surface and / or a curvature of a posterior lens surface . The value of the ideal age-speci fic eye parameter may be obtained according to the literature about emmetropic children and / or according to previous measurements of emmetropic children, wherein the children are of the same age group as the patient . The value of the ideal agespeci fic eye parameter may comprise a median or average value of the measurements of the emmetropic children of the same age group as the patient .

[0024] The compensation basic magnitude derived based on a deviation of the defocus magnitude of the patient from the ideal age-speci fic defocus magnitude may be a magnitude at a distance from the optical axis of the eye . It may be defined as the di f ference between the defocus magnitude of the patientand the ideal age-speci fic defocus magnitude . This takes into consideration that some amount of defocus is present also in emmetropic children . Alternatively or additionally, the compensation basic magnitude may be defined according to the di fference between the defocus magnitude of the patient and the ideal age-speci fic defocus magnitude multiplied by a proportionality factor . The proportionality factor may be between 0 . 5 and 2 .

[0025] A compensation target may be defined . The compensation target may correspond to the compensation basic magnitude of the patient . Alternatively or additionally, the compensation target may correspond a factor of 1 . 5 of the compensation basic magnitude of the patient . This has the advantage of providing a safety margin for myopia control .

[0026] The invention overcomes the limitation of the prior art which cannot measure the amount of peripheral defocus in near viewing because the light is blocked by the constricted pupils at near fixation . The peripheral lens geometry may be reconstructed based on a large sample of children who are experiencing the process of emmetropi zation to myopia onset to calculate the age-speci fic ideal defocus magnitude .

[0027] In one embodiment , providing an accommodative eye model comprises cross validating the accommodative eye model using data of normal adults for the at least one input eye parameter . The data of normal adults may comprise the types of eye parameters described above . Through cross validation, it may be confirmed that the accommodation adj ustment leads to the correct modelling for near vision . In particular, it may be validated that the near-vision parameters are reproduced for the normal adults data using the accommodative eye model with accommodation adj ustment . This way, a normal defocus magnitude may be defined and a defocus model may be established .

[0028] Each eye parameter in the data of normal adults may have a value for the accommodation states of distance viewing, intermediate viewing, and / or near viewing . The value of the eye parameter for distance viewing may be the value of the eye parameter in the relaxed state of the eye . The distance of the obj ect to the eye defining distance viewing may be 1 m to1000 , preferably 1 . 5 m to 3 m . The value of the eye parameter for intermediate viewing may be its value in an accommodation state corresponding to intermediate distance viewing . The distance of the obj ect to the eye defining intermediate distance viewing may be 20 cm to 1 m, preferably 25 cm to 50 cm . The value of the eye parameter for near viewing may be its value in an accommodation state corresponding to near viewing . The distance for near viewing may be 5 cm to 20 m, preferably 10 cm to 15 cm .

[0029] In an embodiment , only two accommodation states are considered, in particular only the distance viewing and near viewing accommodation states . Alternatively or additionally, more than three accommodation states of the eye may be taken into account , wherein a plurality of distances of the obj ect to the eye are defined and / or values of the eye parameters are given for a plurality of distances of the obj ect to the eye .

[0030] The values of the eye parameters may be the same for all accommodation states , in particular for those eye parameters which do not change based on accommodation . The values may be di f ferent for each of the accommodation states , in particular for those eye parameters on which accommodation of the eye has an impact .

[0031] A second aspect of the invention is a product comprising an ophthalmic lens for myopia control or a representation which is located on a data medium in the form of computer- readable data and is of the ophthalmic lens for myopia controlwith instructions for the production thereof , wherein the ophthalmic lens for myopia control comprises a compensation basic magnitude derived according to the inventive method according to the first aspect of the invention .

[0032] A third aspect of the invention is a computer program having program code for carrying out all method steps of the inventive method according to the first aspect of the invention when the computer program is loaded in a computer and / or executed in a computer .

[0033] A fourth aspect of the invention is a computer-readable medium comprising a computer program according to the third aspect of the invention .

[0034] A fi fth aspect of the invention is a computer having a processor and having a data medium, on which a computer program according to the third aspect of the invention is stored and which is configured to carry out a method according to the first aspect of the invention .

[0035] A sixth aspect of the invention is a method for producing an ophthalmic lens for myopia control , comprising a method according to the first aspect of the invention, and manufacturing the ophthalmic lens for myopia control according to the design .

[0036] The ophthalmic lens for myopia control may be a spectacle lens or a contact lens . Contact lenses suitable for being used within the invention are disclosed in ISO 18369-1 : 2017 (E ) . Suitable contact lenses may be soft and / or rigid contact lenses . The ophthalmic lens for myopia control may comprise any kind of soft or rigid contact lenses , in particular "conventional" contact lenses designed to correct the vi-sion by means of their optical power as well as so-called or- thokeratological contact lenses , also referred to as "OrthoK lenses" , that are designed to influence the shape of the cornea of the eye while wearing such lenses . The ophthalmic lens may be suitable for myopia control in children and / or adolescence .

[0037] The ophthalmic lens for myopia control may be produced in such a way as to provide the defocus magnitude of the patient derived according to the inventive method . Preferably, the ophthalmic lens for myopia control may be produced in such a way as to provide a defocus corresponding to the compensation basic magnitude of the patient derived according to the inventive method . This has the advantage of the ophthalmic lens for myopia control correcting for the defocus only so far as it exceeds the age-speci fic ideal defocus found in emmetropic children . Alternatively or additionally, the ophthalmic lens may be produced in such a way as to provide a defocus corresponding to a factor of 1 . 5 of the compensation basic magnitude of the patient derived according to the inventive method . In this case a factor 1 . 5 higher defocus provides an overcorrection, which may be considered a safety margin for myopia control .

[0038] Embodiments of the invention are described with reference to the attached drawings . These drawings show :Fig . la-c : Schematically the defocus model based on the accommodative eye model ;Fig . 2a-c : Schematically the accommodation states included in an accommodative eye model ;Fig . 3 : The peripheral focus obtained according to the accommodative eye model ;Fig. 4: The steps required for deriving a compensation basic magnitude;Fig. 5a, b Schematically an embodiment of ophthalmic lens customization .

[0039] Fig. la shows schematically the elements of the defocus model comprising the following components of the accommodative eye model 11: a cornea 1, eye lens 2 with anterior lens surface 3 and posterior lens surface 4, retina 5 and optical axis 10. Ray tracing is indicated by distance viewing rays 6, which are more central than outer near-viewing rays 7. In the accommodative eye model 11, the cornea 1 has a corneal thickness, an anterior corneal curvature and a posterior corneal curvature .

[0040] Fig. lb and 1c show how the defocus model is established: The distance-viewing ray tracing illustrated in Fig. lb resulting in a distance-viewing focal plane 8 is combined with the near-viewing ray tracing illustrated in Fig. 1c resulting in a near-viewing focal plane 9. More peripheral retinal areas are involved in near viewing. In the more peripheral areas, defocus is greater.

[0041] Ray tracing through the accommodative eye model 11 yields a distance-viewing focal plane 8, which has a larger radius of curvature than the retina 5, but a smaller radius of curvature than a near-viewing focal plane 9.

[0042] Fig. 2a illustrates the ray tracing performed with the accommodative eye model 11 for distance viewing accommodation. The object has a distance of 2000 mm from the eye. The light rays have a small angle to the optical axis 10 of the eye. Theresulting distance-viewing focal plane 8 has a radius of curvature slightly larger than that of the retina 5 . The defocus is therefore small .

[0043] Fig . 2b illustrates the ray tracing performed with the accommodative eye model for intermediate viewing accommodation . The obj ect has a distance of 250 mm from the eye . The intermediate-viewing rays 12 have a larger angle to the optical axis 10 of the eye than in the case of distance viewing accommodation . The resulting intermediate-viewing focal plane 13 has a radius of curvature larger than the retina 5 and larger than the distance-viewing focal plane 8 .

[0044] Fig . 2c illustrates the ray tracing performed with the accommodative eye model for near viewing accommodation . The obj ect has a distance of 100 mm from the eye . The near-viewing rays 7 have a larger angle to the optical axis 10 of the eye than in the case of intermediate viewing accommodation . The resulting near-viewing focal plane 9 has a radius of curvature larger than the intermediate-viewing focal plane 13 .

[0045] According to the embodiments of Fig . 2a-c, the model may be cross validated based on a dataset of normal adults ' eye parameters for di f ferent accommodation states . The cross validation ensures that the accommodation adj ustment of the accommodative eye model reproduces the eye parameters of intermediate vision and / or near vision . While the inventive method is directed to myopia control in particular in children and adolescents , the model assumes that the accommodation adj ustment modelling is independent of the presence of myopia and the age of the patient . Therefore , a cross validation based on non-myopic adults is suitable . The following dataset of normal adult eye parameters is used :

[0046] The resulting defocus for the cases of distance viewing accommodation, intermediate viewing accommodation, and near viewing accommodation according to the accommodative eye model 11 in the cross validation are shown in Fig. 3. The defocus magnitude is determined as the difference between the distance-viewing focal plane and the near-viewing focal plane for each of the accommodation states. The defocus magnitude in diopters is plotted against the two-dimensional plane perpendicular to the optical axis 10 of the eye. The fovea 14 is in the center. The amount of defocus for distance viewing accommodation 15 is smallest and the amount of defocus for near viewing accommodation 17 is largest, with an intermediate amount for the defocus for intermediate viewing accommodation 16. The difference is most pronounced in the peripheral areas further away from the optical axis 10.

[0047] Fig. 4 shows the steps of inputting an age-specific emmetropic dataset 20 to the accommodative eye model 11, which results in the output 23 of an age-specific ideal defocus 24. Using data from an individual myopic eye 21 as input 22 to the accommodative eye model 11 results in an individual defocus 25 as the output 23. The difference A of the age-specific ideal defocus 24 and the individual defocus 25 is the defocus compensation 26.

[0048] Fig. 5a, Fig. 5b illustrate the customization of a spectacle lens (Fig. 5a) and a contact lens (Fig. 5b) for myopia control with the defocus compensation. In detail, Fig 5a shows the effect of a spectacle lens 18 on the peripheral defocus, Fig 5b shows the effect of a contact lens 19 with appropriate optical power on the peripheral defocus. As a third alternative (not shown) , it is possible to achieve the desired effect on the peripheral defocus by using an orthokeratologi- cal contact lens 19 with an appropriate design.List of reference symbols :1 cornea2 eye lens3 anterior lens surface4 posterior lens surface5 retina6 distance-viewing rays7 near-viewing rays8 distance-viewing focal plane9 near-viewing focal plane10 optical axis of the eye11 accommodative eye model12 intermediate viewing rays13 intermediate viewing focal plane14 fovea15 defocus for distance viewing16 defocus for intermediate viewing17 defocus for near viewing18 spectacle lens19 contact lens20 age-speci fic emmetropic dataset21 individual myopic eye data22 input to the accommodative eye model23 output of the accommodative eye model24 age-speci fic ideal defocus25 individual defocus26 defocus compensation

Claims

Claims1. Computer-implemented method for customizing defocus for designing an ophthalmic lens (18, 19) for myopia control for the purposes of using the design for the production of an ophthalmic lens (18, 19) for myopia control comprising the following steps: a) Providing an accommodative eye model (11) comprising at least one input eye parameter (22) and at least one accommodation adjustment, wherein the accommodative eye model (11) outputs a distance-viewing focal plane (8) and a near-viewing focal plane (9) , wherein the distance-viewing focal plane (8) is based on the at least one input eye parameter, wherein the near-viewing focal plane (9) is based on the at least one input eye parameter (22) and the at least one accommodation adjustment ; b) Providing a defocus model based on the accommodative eye model (11) , wherein a defocus magnitude is defined based on a difference between the distance-viewing focal plane (8) of the accommodative eye model (11) and the near-viewing focal plane (9) of the accommodative eye model (11) ; c) Deriving a defocus magnitude (25) of a patient based on the defocus model, wherein at least one individual eye parameter value of the patient is provided as the at least one input eye parameter (22) of the accommodative eye model (11) , wherein the patient is of an age group; d) Deriving an ideal age-specific defocus magnitude (24) based on the defocus model, wherein at least one ideal eye parameter value specific to the patient's age groupis provided as the input eye parameter (22) of the accommodative eye model (11) ; e) Deriving a compensation basic magnitude (26) of the ophthalmic lens (18, 19) for myopia control based on a difference of the defocus magnitude (25) of the patient from the ideal age-specific defocus magnitude (24) , wherein the compensation basic magnitude (26) is proportional to the difference between the defocus magnitude (25) of the patient and the ideal age-specific defocus magnitude (24) .

2. Method according to Claim 1, characterized in that the value of the at least one ideal eye parameter is obtained according to the literature about emmetropic children and / or according to previous measurements of emmetropic children, wherein the children are of the same age group as the patient.

3. Method according to Claim 1 or 2, characterized in that the distance-viewing focal plane (8) and / or the near-viewing focal plane (9) are determined by ensuring that the fovea (14) is always in focus and / or by ensuring that a Strehl ratio of a point spread function is at a maximum.

4. Method according to any of the Claims 1 to 3, characterized in that providing an accommodative eye model (11) comprises cross validating the accommodative eye model (11) using data of normal adults for the at least one input eye parameter .

5. Computer program having program code for carrying out all method steps according to any one of Claims 1 to 4 when the computer program is loaded in a computer and / or executed in a computer.

6. Computer-readable medium comprising a computer program according to Claim 5.

7. Computer having a processor and having a data medium, on which a computer program according to Claim 5 is stored and which is configured to carry out a method according to any one of Claims 1 to 4.

8. Method for producing an ophthalmic lens (18, 19) for myopia control, comprising a method according to any one of Claims 1 to 4, and manufacturing the ophthalmic lens (18, 19) for myopia control according to the design.

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