NL2005486C2

NL2005486C2 - Intra ocular lens.

Info

Publication number: NL2005486C2
Application number: NL2005486A
Authority: NL
Inventors: Bernardus Franciscus Maria Wanders; Walter Bernardus Johannes Wolterinck
Original assignee: Oculentis B V
Priority date: 2010-10-08
Filing date: 2010-10-08
Publication date: 2011-09-20
Also published as: NL2005486A

Description

Intra ocular lens

Background 5

The present invention relates to an intra ocular lens (IOL) comprising a posterior surface and an anterior surface.

The emulation of human eye functionality is a challenge to modem medicine and 10 technology. The human eye substantially has four optic elements: cornea, iris, crystalline lens and retina. The cornea provides a catching of a raw image of the environment. Due to the difference between the refractive index of air and of the cornea (nc « 1.376), the cornea with its refractive power of about 40 dpt contributes the main part of the refractive power of the eye. Next optical element in the human eye is the 15 iris. The iris or iris diaphragm has two functions: (i) The regulation of light intensity, and (ii) regulation of depth of field or depth of focus. Its functioning is based upon a delicate interaction with the accommodation of the crystalline lens and thus provides good and clear vision of the healthy eye. Behind the iris, the crystalline lens provides the optical fine tuning in terms of precise imaging. Dependent on vision range, the 20 crystalline lens varies its shape and in that way images the raw image, delivered by the cornea, to the retina precisely. This effect is referred to as accommodation. The ability of accommodation starts decreasing at an age of about 40 years and will usually be more are less lost at the age of about 60. With advancing age, the crystalline lens often becomes hazy, which process often ends in a more or less complete loss of vision, 25 diagnosed as cataract. Finally, light will be received on the retina. The sensitivity of the retina is comparable to an ultra wide range optical film of about 10 to 40 DIN. It conducts electro-optical signals to the brain, where the image is interpreted.

It is common practise in IOL design to describe all these high precise and interacting 30 functions by using a quite simple model consisting of two thick lenses. Furthermore, the crystalline lens exact purpose and function was long time underestimated. Maybe it is due to its smaller amount to refractive power (about 19 dpt) in comparison to the cornea, or because of the more or less complete loss of its dynamic function in case of 2 cataract patients. Meanwhile, several variations in lens shape, i.e. equiconvex, biconvex, plano-convex, equiconcave, biconcave, plano-concave, meniscus and aspheric lens designs for enhancing the imaging quality are commonly in use. The state of the art for IOL design is the so called optimisation of IOL parameters by using ray 5 tracing programs. This calculation is based on a two thick lens eye model, in which the lens shape is an input parameter.

Numerous optical models of the human eye have been developed up to now. Following L. Thibos (Thibos LN, Ye M, Zhang X, Bradley A., A new optical model of the human 10 eye. Optics and Photonics News 1993;4:12.), these models can conditionally be divided into anatomically-accurate models and analytical models. The goal of an anatomical model is to match gross anatomy of the human eye and to at least model the paraxial geometrical optics of the eye’s thick lens system. Due to the complexity of implementation, an accurate anatomical model is hardly suitable for simulations of 15 visual performance. To the contrary, by avoiding anatomical details, i.e. by treating the eye as an equivalent system of refracting surfaces with the appropriate aberrations, apertures, reflection and absorption coefficients, an analytical model can be obtained that ignores the eye anatomy completely. Analytical models are suitable in cases when the optical performance of the eye should be estimated with high accuracy irrelevant to 20 its real structure. An acceptable compromise is a simplified anatomical model that comprises a physically correct description of the eye, including its dimensions and optical properties. Typical parameters of the human eye can be found in many publications, e.g. in OSA Handbook of Optics or in the well-known description of the “standard military eyeball” model MIL-HDBK-141. References to several widely-used 25 physical models of the eye are cited in: Liou HL, Brennan NA, ‘The prediction of spherical aberration with schematic eyes”, Ophthalmic Physiol Opt 1996;16:348-54, in Thibos LN, Ye M, Zhang X, Bradley A., “The chromatic eye: a new reduced-eye model of ocular chromatic aberration in humans”, Appl Opt 1992;31:3594-600, in R. Navarro, J. antamaria, and J. Bescos, “Accommodation-dependent model of the human 30 eye with aspherics”, Institute de Optica, Serrano 121, 28006 Madrid, Spain, in Larry N. Thibos and Arthur Bradley, “Modelling the Refractive and Neuro-Sensor Systems of the Eye”, School of Optometry, Indiana University. Bloomington, IN 47405, and in 3

Atchison & Smith, “Optics of the Human Eye”,, Butterworth & Heinemann publisher 2000.

In patent literature, many so called aberration free IOL designs are described.

5 Reference is made to EP1850793, EP1857077, W02004/090611 and US2006279697, which are incorporated by reference as if fully set forth. All of them describe the IOL shapes with either one or both surfaces of the IOL shapes to be aspheric and the shape is defined by a conic constant. These IOL shapes are optimised by ray tracing or iteration using a certain eye model, while considering the specific optical condition 10 behind the cornea. This method implicitly assumes that the retina is located at the back focal plane of the optical system.

Summary of the Invention 15 The invention aims provide a method for designing an intraocular lens, and a resulting IOL, that contributes almost zero or a pre-specified amount of spherical aberration to a wave front passing through the IOL.

According to a first aspect of the invention this is realized with an intra ocular lens 20 (IOL) comprising a posterior surface and an anterior surface, said posterior surface having a curvature which is optimised for providing a predefined spherical aberration, wherein said curvature is optimized using the posterior chamber depth (PCD) of an eye in which the IOL is to be inserted.

25 The invention furthermore provides a method for producing a customized IOL for an eye of a person, said IOL having an anterior side and a posterior side, said method comprising the steps of: - Measure at least one biometric value of said eye of said person from which a posterior chamber depth (PCD) of said eye can be derived; 30 - calculating the curvature of said posterior surface for said IOL for said person using said measured biometric value; - producing said IOL having said posterior surface curvature.

4

The invention provides a method which enlarges the inflexible two thick lens eye model and which introduces shape fine tuning for IOL design taking into account the optical properties of the crystalline lens separately. The invention is therewith of such 5 precision, that not only a preferred optical implant can be designed for cataract patients, but also for patients having presbyopic eyesight. The invention uses measurable parameters, the optical power and the conic constant. The refractive power of the cornea and the position of the crystalline lens behind the cornea lead to a manufacturer specific “A” constant of an IOL. However, for shape fine tuning of the IOL, the lens is 10 considered as detached optical device, separated from the two lens model. Shape fine tuning is done by taking into account third order aberration, the higher order aberration terms might be taken into consideration. The third order aberration terms are in geometric optics also known as “Seidel” aberrations, whereas the spherical aberration effects the imaging at most optical modelling of finite element surface displacements 15 using commercial software, see Keith B. Doyle, Victor L. Genberg, Gregory J.

Michels, Gary R. Bisson, SPIE publication Sigmadyne Inc., 803 West Avenue, Rochester, NY 14611. Thus the invention focuses on the effect of spherical aberration. Using the calculations mentioned above, taking into account posterior chamber depth and directed spherical aberration, the IOL power and the conic constant are determined.

20

It was found that for a biconvex IOL situated in a human eye, the spherical aberration generated by the posterior surface is many times bigger than the spherical aberration generated by the anterior surface.

25 For a biconvex IOL or more general an IOL with significant negative curvature of the posterior surface, it is found that in most cases it is sufficient to correct for the spherical aberration resulting from the posterior surface only.

Using the current method, it is also possible to correct for the anterior surface by taking 30 in account the optical power of the posterior surface.

The amount of spherical aberration generated by the posterior surface of a biconvex lens can be corrected on the posterior surface itself or on the anterior surface.

5

The amount of spherical aberration generated by the anterior surface of a biconvex lens can be corrected on the anterior surface itself or on the posterior surface.

5 The posterior chamber depth can be found by direct measurement by using for example a commercial available instrument to perform the biometry of the eye such as the IOLMaster, Zeiss Germany, Lenstor LS900, Haag Streit, Switzerland or a Acoustic method called A-scan or by applying statistical found correlations between the required optical power of the IOL and the posterior chamber depth. By examination of large sets 10 of biometric data, surprisingly a strong correlation, in fact, a linear correlation, was found between the calculated required optical power for the IOL implant and the posterior chamber length. The method according this invention integrated into the biometry software of the above mentioned instruments will pave the way to efficient and fast customized IOL calculation without complicated ray tracing and use of model 15 eyes. The system would then calculate the specific conic constant or coefficient needed to minimize the spherical aberration for said IOL for said patient.

In an embodiment, the curvature is a mathematical function of the PCD.

20 In an embodiment, the mathematical function is defined as or is equivalent to r2/R2 l + ^jl-(l + k)r2 /R2 ’ with h = niR3 (1__1 x2(fli+fl2 n2

n; R PCD PCD R

in case of zero additional spherical aberration or, when a specified amount of spherical 25 aberration should be added, with , n7R3 .1 1 72,n,+n7 H,, 8R3 k = -L1-(---) (—-1—-) +-<7 , n\ R PCD PCD R nx-n2

In which equations the used parameters are: k = -e2 conic constant, R Radius of curvature, 30 r radial distance from optical axis, 6 z height or sagitta of refracting surface, nx refractive index of the material of the IOL, n2 refractive index of the vitreous body of the eye, PCD Posterior chamber depth, 5 a Coefficient specifying additional spherical aberration.

In an embodiment, said curvature is optimised using ray-tracing using the PCD as a parameter.

10 In an embodiment, the PCD is obtained using a biometric measurement on an eye from which values relating to the size of the measured eye can be derived.

In an embodiment, the PCD is obtained using a predetermined relation between PCD values determined for persons in a population and calculated power for the IOL for the 15 persons that population. Thus, when determining these values for each person, it was found that statistical analysis showed strong relations.

In an embodiment, the method comprises the step of calculating a nominal IOL power of a lens for said eye from said biometric value using Haigis, SRK, Holladay or similar 20 formula’s. Using these methods, it is possible to calculate the optical power, in dioptre, of an eye from biometric values, like size o the eye or even PCD. In an embodiment thereof, the method further comprises the step of determining said PCD of that person using an obtained statistical relation between the nominal IOL power of a population and the PCD values of that population. In an embodiment thereof, the statistical relation 25 is expressed in a regression formula. Thus, from measurements on a set of persons, a statistical relation was found. And, in fact, a simple linear relation already showed a useful result in practise.

In an embodiment of the method, the biometric value is said PCD of said person.

30

In an embodiment, the method further comprises the step of calculating the curvature of the anterior surface based upon the calculated curvature of said posterior surface, said calculation of said anterior surface using ray-tracing.

7

In an embodiment, the method further comprises the step of inserting said IOL in the eye of said person.

5 The invention further relates to a method for providing a person with an IOL, said method comprising the steps of: -providing a set of IOL’s according to claim 1, said IOL’s having stepwise increasing dioptre values; - Measure at least one biometric value of said eye of said person from which a dioptre 10 value of an existing lens in said eye can be derived; - selecting that IOL from said set of IOL’s which has a dioptre closest to the determined dioptre of said person.

Thus a set of largely standardized IOL’s can be provided which correct for both optical 15 power (dioptre) and spherical aberration. Thus, the optical quality could be significantly improved.

The invention further relates to a computer program product for engineering a curvature of the posterior surface of an IOL, said computer program product, when 20 running on a processor, performs steps comprising obtaining a parameter from which a posterior chamber depth (PCD) value of a human eye can be derived, obtaining a predetermined set value for a spherical aberration of said IOL, and calculating the height of the posterior IOL surface as a function of: - the distance from an optical axis of said IOL, 25 - said parameter from which said posterior chamber depth value can be derived, and - said predetermined set value for a spherical aberration of said IOL.

In an embodiment, the computer program product is further arranged for performing the steps of one or more of the method described above. In particular, the equations and 30 calculation method of this description can be implemented n the computer program product. The computer program product can be implemented on a data carrier, in a computer memory, but also hardware implemented in an apparatus.

8

In an embodiment, the invention further relates to an apparatus for determining size parameters of a human eye, said apparatus comprising the computer program product of any one or the preceding claims running on said apparatus.

5 The current invention can be implemented into the controlling of IOL production devices or apparatuses, or in can be implemented into measuring devices or measuring apparatuses for measuring a biometric parameter of an eye. Furthermore, the current invention can be implemented into computer software running on a general purpose computer, on a production apparatus or on a measuring apparatus described in, but not 10 limited to, apparatuses described in this description.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Various aspects of this description may form the basis of one or more divisional applications.

15

Description of the Drawings

The invention will be further elucidated referring to an embodiment of an IOL explained in the attached drawings, showing in: 20

Figure 1 a schematic human eye;

Figure 2 the human eye of figure 1 with an IOL;

Figure 3 an example of an IOL in front view;

Figure 4 definition of the posterior chamber depth, PCD; 25 Figure 5 definition of PCD, when neglecting the lens thickness;

Figure 6 rays diffracted on a spherical surface of refractive index transition;

Figure 7 graph showing PCD as function of Dioptre and statistical regression line.

Detailed Description of Embodiments 30

In figure 1, a schematic view of a human eye 100 with its natural lens 106 is shown. The eye has a vitreous body 101 and cornea 102. The eye has an anterior chamber 103, iris 104 and ciliary muscle 105 which hold the lens. The eye has a posterior chamber 9 107. In figure 2, the eye 100 is shown with an intra ocular lens 1 replacing the original lens 106.

In figure 3, an embodiment of an intra ocular lens (IOL) 1 is shown which has haptics 2 5 and a lens zone or lens part 3 in front view, showing the anterior surface of the IOL 1. The lens part 3 is the actual optically active part of the IOL 1. The haptics 2 can have a different shape. In this embodiment, lens part 3 has a central part 6 which is usually substantially circular. It may deviate a little from an absolute circle, but in most embodiments it is as round or circular as possible in the specific further lens design.

10 The lens part 3 further has a meridian part in a recess area. This recess is below the surface of the curved surface of the remaining lens part 4 of lens part 3.

First, a theoretical basis for the invention is provided. It can be shown that up to the fourth order the primary aberrations for a spherical surface or thin lens is given by 15 W(r,6,h) = assr4 + acshr3 cos(0) + aash2r2 cos(0)2 +adsh2r2 +a0/z3rcos(0) (1)

The first term is called spherical aberration: 20 Wspherical(r) = assr4 (2)

It can be shown that the aberration for a spherical refractive surface is (“Aberrations Theory Made Simple ”, Virendra N. Mahajan, SPIE Optical engineering Press, 1991): 25 W„,IM(r) = ~”2( V”') (| - VAT - <3>

8 n{ K SZ K SZ

See figure 6, with R radius of curvature of the refracting surface, (sign convention: R < 0 for convex 30 surfaces, R>0 for concave surfaces) nx refractive index of media left of refractive surface 10 n2 refractive index of media right of refractive surface S2 image distance r distance from the optical axis 5 This equations shows that the amount of spherical aberration is dependent on the refractive indexes, the radius of curvature of the refractive surface and the image distance S2. For an IOL implanted in human eye the image distance S2 is equal to the distance between the posterior surface of the IOL and the retina. If this distance is different the implanted IOL has the wrong optical power: 10 W (r)= ~n2(n2 ~ni)( 1 1 \2(n2 ni+n2} 4 ,a}

sphericaA ’ 8^2 R PCD R PCD K

Using this equation it was found that in the amount of spherical aberration introduced by a convex surface (R<0) is much larger than the amount of aberration introduced by a 15 concave refractive surface (R>0). In general, for a biconvex IOL the amount of aberration introduced by the posterior surface of the IOL is therefore much larger than the amount of aberration introduced by the anterior surface of the IOL. For most cases it is therefore sufficient to consider only the spherical aberration generated by the posterior surface.

20

It is also possible to account for both the spherical aberration generated by the posterior and anterior surface. By applying the formula for the generated spherical aberration both for the anterior and posterior surface. Note that by applying the formula on the anterior surface a virtual PCD should be used. By the refracting power of the posterior 25 surface a different PCD is seen by the anterior surface.

Aberration added by a conical surface

Spherical surfaces are conical surfaces with zero eccentricity. A conical surface can be 30 described by equation (5): r2/R2 z =-1 — (5) l + yll-(l + k)r2/R2 11 with : k = -e2 conic constant (6) R Radius of curvature 5 r radial distance from optical axis z height k is the conic constant. The conic constant is less than -1 for hyperbolas, -1 for parabolas, between -1 and 0 for ellipses, 0 for spheres, and greater than 0 for oblate 10 ellipsoids

For an eccentricity of zero, the spherical aberration introduced by a conic refractive surface is equal to the amount of spherical aberration introduced by a spherical refractive surface. For eccentricity value other than zero it can be shown that the 15 additional spherical aberration is equal to: (7)

oK

The total amount of spherical aberration generated by conic surface can now be 20 calculated by :

spherical \ (R pCD^R ptf) ^2 l\RS

So by choosing the conic constant k the amount of spherical aberration introduced by the refracting surface can set to a desired value.

25

Example conic surface with zero spherical aberration: W (r)=-»2(»2-»l)(l__L)V^_R1+fl2V4+(|i _w)^r4=0 sphencA ) 8^2 iR p^^p ƒ>££) 1 30 (9) 12

Gives: _ n2R 1 1 +»2 _^2_\ no) /¾2 i? PCD { PCD R} { 5 When desired it is also possible to add a specified amount of spherical aberration <7 • r4 to the wave front.

ttt s \ (^2 ),1 1 ..2 "t" \ 4 / \ 4 /i i\ sphencaA ) ^ 2 ^ pC£) R ƒ>££>' 10 With cr • r4 is the term specifying the additional spherical aberration. Solving this equation gives: k = tP l_J_ 2 nLvn^_n^ n2x R PCD PCD R nx-n2 15 Obtaining the Posterior Chamber Depth with a regression formulae

By analysing large amount of biometric data (preoperative anterior chamber depth, axial length and corneal radius), it was discovered that a strong statistical correlation exists between the calculated refractive power for the IOL implant (Calculation 20 according to HAGIS from the biometric data) and the posterior chamber depth. The posterior chamber depth is herein defined as the distance between the posterior surface of the implanted IOL and the retina (see figure 4).

The correlation can be obtained in the following way.

25

Step 1

From the preoperative anterior chamber depth and axial length measured with for example ultrasound and the corneal radius measured with for example a topographer the required IOL optical power can be calculated using a suitable IOL optical power 13 calculation formula. For example with HAIGIS, SRK/T, Holladay or similar, formula. When using the HAIGIS formula the required optical IOL optical power D is calculated by: 5 D = —----— (13) ALpr nlz — d

With: z = DC +-c£— DC = S^i

1 -refdBC RC

D refractive power of the IOL 10 DC refractive corneal power RC corneal radius

nC (Fictitious) refractive index of the cornea dBC vertex distance between cornea and glasses d optical ACD

15 AL (Preoperative) axial length n refractive index of aqueous and vitreous (1.336) ref desired (residual) refraction after implant, normally 0 dioptres

Step 2 20

From the same biometric data of step 1, the optical anterior chamber depth d for the IOL to be inserted is calculated with the Haigis regression formula: d = aO + a\ VKpr + a2 ALpr (14) 25

With: aO = ACDconst-a\-MW(VKpr)-a2-MW(ALpr) (15) ALpr The preoperative axial length measured with for example ultrasound 14 VK The pre-operative anterior chamber depth ACDconst ACD constant from manufacturer MW(AL) Means of the pre-operative axial length -23.39 mm MW (VKpr) Means of the pre-operative anterior chamber depth -3.37 mm 5

Step 3 10 From the anterior chamber depth determined in step 2, the posterior chamber depth can be calculated by subtracting the found anterior chamber depth from the measured axial length of the eye. If the lens thickness can be neglected we get: PCD = ALpr - d (16) 15 with: PCD Posterior chamber depth ALpr Preoperative axial length 20 d Optical Anterior Chamber Depth

If the lens thickness cannot be neglected a additional fraction of the lens thickness should be subtracted from the preoperative axial length.

25 Note: It is also possible to use the pre-operative chamber depth directly to calculate the posterior chamber depth. This is however likely to be less accurate.

Step 4 30 This calculation was repeated for many measurements of different patients eyes. Using statistical methods on the obtained dataset, a correlation was found between the calculated optical power of step 1 and the posterior chamber depth of step 3.

15

In an embodiment, a linear equation was surprisingly found to be accurate enough to fit the dataset, using: 5 PCD = bO + bb® (17) with PCD Posterior Chamber Depth in mm bO coefficient (typical 23.868 mm) 10 bl coefficient (typical-0.262 mm/Dioptre) d) calculated power for IOL in Dioptre

Advantages

15 The required conic constant to correct the spherical aberration generated by the IOL

surface(s) requires only one additional biometric parameter, the Posterior Chamber Depth (PCD).

Standard IOL

20 It is shown that the required conic constant to correct for the spherical aberration of the IOL is depending only on the PCD, paraxial radius of the posterior surface of the IOL, and the IOL material. It is also shown that the PCD has a strong correlation with the optical power of the IOL (Figure 7). The paraxial radius of curvature of the IOL results from the optical power of the IOL and the shape of the IOL. (distribution of the optical 25 power between the anterior and posterior surface). This means that when producing IOL’s in mass production the amount of needed correction for spherical aberration can be estimated accurately on the basis of the optical power of the IOL.

In fact, this dependency and calculation method allows several methods and IOL 30 designs which show a better performance than IOL’s made so far. First, it is possible to produce mass production IOL with a set spherical aberration, usually zero. A set of IOL’s can thus be made, each having a designed dioptre and corrected to a set spherical aberration.

16

In another method, resulting in an IOL with a different design, it allows easy production of a custom made IOL which is optimised to the eye of a particular patient. In this case the PCD is not determined with a regression formulae but calculated from the measured biometric data of the patient eye only (step 1,2 and 3. Step 4 not needed), 5 or may even be measured directly. The PCD can be accurately calculated from for example the biometric measurement which is performed with a specific type of ultrasound or optical measurement system. An example of such a system is given above. From this measurement the PCD of a specific patient could be determined and the optimal IOL with the optimal correction for spherical aberration can be calculated.

10

The current invention is based on the insight that it can be advantageously to correct the spherical aberration on the same surface where the spherical aberration is generated.

Examples

15 Equiconvex IOL

In this example the conic constant for the posterior surface of an equiconvex IOL is calculated. The optical power calculated according to Haigis is 22 Dioptre with zero spherical aberration.

20 For the calculation of the correcting conic factor we need the posterior radius of the IOL. The radius of the posterior lens surface can be easily calculated from the IOL power and shape factor and refractive indexes. For a equiconvex IOL, the optical power is equally distributed between the posterior and anterior surface. The optical power of the posterior surface is therefore 11 dioptre. From the paraxial power we calculate the 25 posterior radius rb: = nlZn1_ b ¢,- posterior with ttjthe refractive index of IOL and /?2 the refractive index of vitreous body of the 30 eye. Selecting 17 ® posterior = 22''2 DioPtre /7, = 1.46 n2 = 1.336 5 rh = -11.3 mm (Negative sign )

The PCD calculated from eq. 17: 10 PCD = 23.868-0.262-22= 18.1 mm.

k = _n2rL(L__1 \2 ,n2 nx+n2

n\ rh PCD rh PCD

When inserting the calculated PCD into this equation, it follows that: , l.336 —ll.33 l l ,2,1.336 1.46 + 1.336, ^ 15 k =--5-(---)(---) = -5.06 1.462 —11.3 18.1 -11.3 18.1

Table 1 Calculated values for the conic constant k . With index n of IOL=1.46

Optical power Anterior radius Posterior radius PCD Conic constant (Dioptre) (mm) (mm) (mm) k ® r/ rt TÖ 24.800 -24.800 Hi -13.5 ~L2 20.667 -20.667 2Ö7 -10.3 IT 17.714 -17.714 Hi Ha

16 15.500 -15.500 191 ^7T

"Ï8 13.778 -13.778 19Ï HÏ

20 12.400 -12.400 ÏN6 H

22 11.273 -11.273 Ï8T Hi

24 10.333 -10.333 1Ï6 H

26 9.538 -9.538 Ï7T H

28 8.857 -8.857 Ï6Ï H

18 3Ö 8.267 -8.267 16.0 TTÖ

Plano-Convex IOL

Next, correction on posterior surface for an plano-convex IOL with a calculated power 5 according to Haigis of 22 dioptre and zero spherical aberration will be demonstrated.

For a plano-convex IOL the optical power is fully situated on the posterior surface. The optical power of the posterior surface is therefore 22 dioptre. From the paraxial power of the posterior surface we calculate the posterior radius: 10 n9 —n, rh ~ posterior

When inserting into this equation the following values: ® posterior = 22 Dioptre

Wj = 1.46 15 «2=1.336

We calculate: rb = -5.6mm (Negative sign!)

The PCD calculated from equation 16 will now be used. Note : The found correlation 20 applies for a specific ACD constant of the IOL. Therefore, the correlation for a planoconvex lens and a equiconvex lens can be slightly different. We thus use: PCD = 23.868-0.262-22 = 18.1mm 25 When inserting the above determined values into equation (10): k = _rhrL(]___1 ,2 (n2 nx+n2

n\ rb PCD {rb PCD

We get: 19 1.336--5.63 1___1 2 1.336 1.46 + 1.336 1.462 -5.6 18.1 -5.6 18.1 ~

Adding spherical aberration 5

Suppose we want a to add spherical aberration of 1 pm at a distance of 1.5 mm from the optical axis. That is the aberration of the wave front with respect to the Gaussian reference sphere is 1 pm at a distance of 1.5 mm from the optical axis after refraction by the posterior surface. It thus follows from equation (11): 10 cr l.54 = MO 3

And thus <7 = 0.000197530 15 When using n2=1.336, nl=1.46, R=-11.22, andPCD=18.1 in equation (12) , n0R3 .1 1 \2,n,+n0 n0. 8i?3 k = -^-(---)(--1—-) +-cr n2, R PCD PCD R nt-n2 20 It follows that k = - 23.0

When using a spherical aberration of -1 pm in the same calculation, we get 25 /1 = 13.0

Backward ray tracing 30 The posterior surface of the IOL can also be constructed and optimised by ray tracing. From geometrical optics it is known that ray path’s are reversible. So it is possible to 20 start the ray tracing from the image and construct the posterior surface of an IOL in such a way that zero or a specified amount of spherical aberration is added by the refracting posterior surface.

5 It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person which are within the scope of protection and the essence of this invention and which are obvious combinations of prior art techniques and the disclosure of this patent.

10

Claims

1. Een intra oculaire lens (IOL) omvattende een posterior oppervlak and an anterior oppervlak, het posterior oppervlak voorzien van een kromming die is 5 geoptimaliseerd voor het verschaffen van een voorafbepaalde sferische aberratie, waarbij de kromming is geoptimaliseerd onder gebruikmaking van de posterior kamer diepte (posterior chamber depth, PCD) van een oog waarin de IOL moet worden geimplanteerd.An intraocular lens (IOL) comprising a posterior surface and an anterior surface, the posterior surface provided with a curvature optimized to provide a predetermined spherical aberration, the curvature optimized using the posterior chamber depth (posterior chamber depth, PCD) of an eye into which the IOL is to be implanted.

2. De IOL van conclusie 1, waarbij de kromming een mathematische functie is van de PCD.The IOL of claim 1, wherein the curvature is a mathematical function of the PCD.

3. De IOL van conclusie 2, waarbij de mathematische functie gedefinieerd is als, of equivalent is aan, K r2/R2 15 z--, = , 1 + ^1-(1 + k)r2/R2 met k = mV__,nx+n2 _ nL n2 KR PCD K PCD R in geval van een additionele sferischcal aberratie nul is of, wanneer een specifieke sferische aberratie zou moeten worden toegevoegd, met 20 k = ^-(—--—fCi+”-L--^)+ 8i?3 g , n2 R PCD PCD R n,-n2 Waarin de gebruikte parameters zijn: k = -e2 conische constante, R kromtestraal, r radiale afstand van de optische as, 25. hoogte of sagitta van het refracterende oppervlak, brekingsindex van het materiaal van de IOL, n2 brekingsindex van het glasachtige lichaam van het oog, PCD Posterior kamer diepte (Posterior chamber depth), cr Coefficient die de toegevoegde sferische aberratie specificeert. 30The IOL of claim 2, wherein the mathematical function is defined as, or equivalent to, K r 2 / R 2 z 2, =, 1 + ^ 1- (1 + k) r 2 / R 2 with k = mV__, nx + n2 _ nL n2 KR PCD K PCD R in case of an additional spherical cal aberration is zero or, if a specific spherical aberration should be added, with 20 k = ^ - (----— fCi + ”- L - ^ ) + 8i? 3 g, n2 R PCD PCD R n, -n2 where the parameters used are: k = -e2 conical constant, R radius of curvature, r radial distance of the optical axis, 25. height or sagittta of the refractive surface, refractive index of the material of the IOL, n2 refractive index of the glassy body of the eye, PCD Posterior chamber depth, cr Coefficient that specifies the added spherical aberration. 30

4. De IOL van conclusie 1, waarbij de kromming is geoptimaliseerd onder gebruikmaking van ray-tracing met de PCD als een parameter.The IOL of claim 1, wherein the curvature is optimized using ray tracing with the PCD as a parameter.

5. De IOL volgens één of meer der voorgaande conclusies, waarbij de PCD is 5 verkregen onder gebruikmaking van een biometrische meting aan een oog waaruit waarden die betrekking hebben op de afmeting van het gemeten oog kunnen worden afgeleid.5. The IOL according to one or more of the preceding claims, wherein the PCD is obtained using a biometric measurement on an eye from which values relating to the size of the measured eye can be derived.

6. De IOL volgens één of meer der voorgaande conclusies, waarbij de PCD is 10 verkregen onder gebruikmaking van een vantevoren bepaalde relatie tussen PCD waarden die bepaald zijn voor personen in een populatie en berekend sterkte van de IOL voor de personen in die populatie.6. The IOL according to one or more of the preceding claims, wherein the PCD is obtained using a predetermined relationship between PCD values determined for persons in a population and calculated strength of the IOL for the persons in that population.

7. Een werkwijze voor het produceren van een op maat gemaakte IOL voor een oog 15 van een person, met de IOL voorzien van een anterior zijde en een posterior zijde, waarbij de werkwijze de stappen omvat van: - Meten van ten minste één biometrische waarde van het oog van de persoon waaruit een posteriore kamerdiepte (posterior chamber depth, PCD) van het oog afgeleid kan worden; 20. berekenen van de kromming of het posteriore oppervlak voor de IOL voor de persoon onder gebruikmaking van de gemeten biometrische waarde; - produceren van de IOL met de posteriore oppervlakte kromming.A method for producing a customized IOL for an eye of a person, the IOL having an anterior side and a posterior side, the method comprising the steps of: - Measuring at least one biometric value from the eye of the person from which a posterior chamber depth (PCD) of the eye can be derived; 20. calculating the curvature or posterior area for the IOL for the person using the measured biometric value; - producing the IOL with the posterior surface curvature.

8. De werkwijze van conclusie 7, omvattende de stap: 25. berekenen van een nominale IOL sterkte van een lens voor het eye uit de biometrische waarde onder gebruikmaking van Haigis, SRK, Holladay, of soortgelijke formules.The method of claim 7, comprising the step of: 25. calculating a nominal IOL strength of a lens for the eye from the biometric value using Haigis, SRK, Holladay, or similar formulas.

9. De werkwijze van conclusie 8, verder omvattende de stap van het bepalen of de 30 PCD van de persoon onder gebruikmaking van een verkregen statistische relatie tussen de nominale IOL sterkte van een populatie en de PCD waarden van die, in het bijzonder omvattende de stap van het bepalen van de optische sterkte of dioptrie van een lens in een oog van de persoon, en het gebruiken van de statistische relatie en de bepaalde optische sterkte voor het bepalen van de PCD.9. The method of claim 8, further comprising the step of determining whether the person's PCD using a obtained statistical relationship between the nominal IOL strength of a population and the PCD values of that, in particular comprising the step of determining the optical strength or diopter of a lens in an eye of the person, and using the statistical relationship and the determined optical strength to determine the PCD.

10. De werkwijze van conclusie 9, waarbij de statistische relatie is uitgedrukt in een regressie formule. 5The method of claim 9, wherein the statistical relationship is expressed in a regression formula. 5

11. De werkwijze van conclusies 7-10, waarbij de biometrisch waarde de PCD van de persoon is.The method of claims 7-10, wherein the biometric value is the person's PCD.

12. De werkwijze van conclusie 7-11, verder omvattende de stap van het berekenen van 10 de kromming van het anteriore oppervlak op basis van de berekende kromming van het posteriore oppervlak, waarbij de berekening van het anteriore oppervlak gebruik maakt van ray-tracing.12. The method of claims 7-11, further comprising the step of calculating the curvature of the anterior surface based on the calculated curvature of the posterior surface, wherein the computation of the anterior surface uses ray tracing.

13. De werkwijze van conclusie 7-12, verder omvattende de stap van het implanteren 15 van de IOL in het oog van de persoon.The method of claims 7-12, further comprising the step of implanting the IOL into the eye of the person.

14. Een werkwijze voor het voorzien van een persoon van een IOL, waarbij de werkwijze de stappen omvat: - verschaffen van een set IOL’s volgens conclusie 1, de IOL’s voozien van 20 stapsgewijs oplopende dioptrie waarden; - Meten van ten minste één biometrische waarde van het oog van de persoon waaruit de dioptrie waarde van een bestaande lens in het oog kan worden afgeleid; - het selecteren van die IOL uit de set IOL’s die een dioptrie heeft die het dichtst ligt bij de vastgestelde dioptrie van die persoon. 25A method of providing an IOL to a person, the method comprising the steps of: - providing a set of IOLs according to claim 1, providing the IOLs with stepwise ascending diopter values; - Measuring at least one biometric value of the eye of the person from which the diopter value of an existing lens in the eye can be derived; - selecting that IOL from the set of IOLs that has a diopter that is closest to the person's established diopter. 25

15. Een computer programma produkt voor het construeren van een kromming van het posteriore oppervlak van een IOL, waarbij het computer programma produkt, wanneer werkend op een processor, de stappen uitvoert omvattende het verkrijgen van een parameter waaruit een posteriore kamerdiepte (PCD) waarde van een 30 menselijk oog kan worden bepaald, het verkrijgen van een voorafbepaalde set waarden voor een sferische aberatie van de IOL, en berekenen van de hoogte van het posteriore IOL oppervlak als een functie van: - de afstand van een optische as van de IOL, - de parameter waaruit de posteriore kamer diepte waarde kan worden bepaald, en - de bepaalde set waarden voor een spherische aberratie van de IOL.A computer program product for constructing a curvature of the posterior surface of an IOL, wherein the computer program product, when operating on a processor, performs the steps of obtaining a parameter from which a posterior chamber depth (PCD) value of a human eye can be determined, obtaining a predetermined set of values for a spherical aberration of the IOL, and calculating the height of the posterior IOL surface as a function of: - the distance of an optical axis from the IOL, - the parameter from which the posterior chamber depth value can be determined, and - the determined set of values for spherical aberration of the IOL.

16. Het computer programma product van conclusie 15, verder ingericht voor het 5 uitvoeren van één of meer van de werkwijze stappen van de voorgaande werkwijze conclusies.16. The computer program product of claim 15, further adapted to perform one or more of the method steps of the preceding method claims.

17. Een inrichting voor het bepalen van afmetingsparameters van een menselijk oog, waarbij de inrichting omvat het computer programma product volgens één van de 10 voorgaande conclusies werkend op de inrichting. -o-o-o-o-o-o-A device for determining size parameters of a human eye, the device comprising the computer program product according to any of the preceding claims operating on the device. -o-o-o-o-o-o-