EP4236757A2

EP4236757A2 - Method of manufacturing lenses for patients with keratoconus

Info

Publication number: EP4236757A2
Application number: EP21835429.8A
Authority: EP
Inventors: Christiaan Jacobus Hubertus FRAMBACH
Original assignee: Frambach BV
Current assignee: Frambach BV
Priority date: 2020-10-29
Filing date: 2021-10-27
Publication date: 2023-09-06
Also published as: WO2022093021A3; NL2026791B1; WO2022093021A2

Abstract

When manufacturing a pair of lenses for improving visual performance in patients with keratoconus (a lens here includes a contact lens, an intraocular lens, and a spectacle grass), the following steps are taken for each eye: determining by means of subjective refraction the most effective conventional lens, with equal spherical and cylindrical power over the entire anterior optical zone, determining by subjective refraction optimal optical parameters for a second optical zone applied to the first optical zone, wherein the patient does not have to hold his/her head in a specific position, which optical parameters are formed by the shape, size, value and course of the strength and position on the first optical zone, manufacturing a lens provided with a first and second optical zone as determined above, and repeating the determination of optimal optical parameters for the second optical zone by means of subjective refraction with the lens inserted or in front of it, and producing an adapted lens when deviating optical parameters are found. Then, in or for each eye, one of the fabricated lenses is either presented or inserted and with both eyes looking repeated the subjective refraction determination of optimal optical parameters for the second optical zones for each eye. Thereafter, a set of final lenses having a first and second optical zone as determined above is manufactured.

Description

Method of manufacturing lenses for patients with keratoconus

DESCRIPTION:

Technical field of the invention

The invention relates to a method of manufacturing lenses for improving visual performance in patients with keratoconus, comprising: for each eye: determining by subjective refraction the most effective conventional lens for that eye while covering or obscuring the other eye, the anterior optical zone of this lens forming a first optical zone of the lenses to be manufactured, determining by means of subjective refraction optimal optical parameters of a second optical zone of the lenses to be manufactured, which optical parameters comprise the sphero-cylindrical power, and manufacturing a set of lenses provided with a first and second optical zone arranged thereon as determined above.

A lens is here understood to mean a contact lens, an intraocular lens and a spectacle glass and a conventional lens here is understood to mean a lens having an optical zone (FOZ) with a sphero-cylindrical power.

Determining the most effective conventional lens by subjective refraction is done by successively holding spherical and cylindrical fitting glasses of different strength in front of each eye to determine the basic power (of the first optical zone) of the lenses to be manufactured, whereby the best base strength is the strength of the pass glass with which the eye sees best.

Background of the invention

A method according to the preamble of claim 1 is known from W02017/123091A1. In this known method the strengths of contact lenses are determined by means of subjective refraction and the optical parameters are determined at the front of the contact lens under binocular conditions. Summary of the invention

An object of the invention is to provide a method of the type described in the preamble with which a set of lenses can be manufactured in a simpler manner than with the known method, wherein the set of lenses produced in this way also improves the visual performance in patients with keratoconus more than with the set of lenses obtained by the known method. To this end, the method according to the invention is characterized in that it further comprises the following steps: for each of the two eyes repeating the determination of optimal optical parameters for the second optical zone by means of subjective refraction with the lens inserted or in front of it, and manufacturing an adapted lens when deviating optical parameters are found, inserting or holding the determined lenses in each eye and repeating with both eyes the determination by subjective refraction of optimal optical parameters for the second optical zones for each eye, and manufacturing a set of final lenses provided with a first and second optical zone as defined above, wherein in determining optimal optical parameters by subjective refraction, in addition to the strength of the optical zones and the position of the second optical zone relative to the first optical zone, furthermore the shape, size and variation of the strength of the second optical zone is determined, wherein the patient does not have to hold his/her head in a specific position during the determination of the optimal optical parameters, and wherein the anterior surface of the second optical zone is on the anterior surface of the first optical zone and thus the second optical zone is not an integral part of the first optical zone.

The measurement is performed in a subjective manner, whereby the patient does not have to adjust the head position for this. The optical portion having a different power from the first optical zone is added to the anterior optical zone (FOZ) in the form of a second optical zone and thus as such is not a complete part of the first optical zone. The added second optical zone can be varied in optical structure, location, diameter, addition and addition course. The first and second optical zones can be varied in light transmittance, wherein the zone of the filter can be varied in diameter. The parameters to be ultimately selected on the front of the contact lens are adjusted under binocular conditions, whereby the patient's head position does not have to be adjusted either.

All the options described above for adjusting the optical zones are possible for both a hard contact lens and a thick soft contact lens. When a soft contact lens for keratoconus is made so thick that it assumes a spherical or toric surface on the front of the eye, this soft contact lens, like a hard contact lens, can be provided with a second optical zone with a more positive power.

One can choose from the following options for the optical structure of the second optical zone (2nd OZ): a. Uniform strength, the strength of which can be chosen variable and more positive in strength with respect to the 1st OZ. To obtain this effect, the 2nd OZ of a contact lens material can also be made with a different refractive index. b. Radially extending strength, in which the central strength in the 2nd OZ has the highest more positive value with respect to the 1st OZ (= the addition) and can vary variably towards the periphery of the 2nd OZ, in a smooth or in zones reduced strength. In addition to the chosen addition, the addition pattern can also be varied. c. Radially extending strength, whereby the peripheral strength in the 2nd OZ has the highest more positive value with respect to the 1st OZ (= the addition) and can vary variably towards the center of the 2nd OZ, in a smooth or in zones reduced strength. In addition to the chosen addition, the addition pattern can also be varied. d. Descending strength from top to bottom, with the highest positive strength relative to the 1st OZ being the highest at the top of the 2nd OZ and can slope downwards smoothly or in zones with reduced strengths. e. Diameter ranging from 0.5mm - 15mm. f. Positioning relative to center of the 1st OZ (relative to the horizontal markings of the rotationally stabilized contact lens and distance to center).

Furthermore, the 1st OZ or the 2nd OZ of the lens can be varied in light transmittance, where there is also the possibility to vary the diameter of the filter in the region of the OZ.

An embodiment of the method according to the invention suitable for manufacturing a set of intraocular lenses is characterized in that: first the cornea of each eye of the patient is measured topographically, then the contact lenses manufactured in claim 1 are placed on the eyes of the patient, then the front of the contact lenses on the eyes are measured topographically, and finally (using software) a power map of an intraocular lens to be manufactured is determined from the difference between the power map of the topographical image of the front of the contact lens and that of the cornea, and on the basis of this a set of intraocular lenses manufactured.

An embodiment of the method according to the invention, which is suitable for manufacturing a set of intraocular lenses, is characterized in that a pin hole is added to the optimum parameters depending on the visual performance.

Furthermore, depending on the visual performance, a filter may be provided in the first and/or second optical zone.

The invention also relates to a method for determining the power of a lens for the correction of keratoconus, comprising: determining the power of a spherical and a cylindrical lens for correcting lower order aberrations using a set of spherical and a set of cylindrical fitting lenses of increasing prescription by visualizing the fitting lenses of each set one by one where the strength of that glass with which it can be seen best forms the strength for correction of lower order aberrations for that eye, and then determining the power of one or more spectacle lenses for correcting one or more of the higher order aberrations: coma, spherical aberration, secondary astigmatism and trefoil; using one or more sets of fitting glasses for each of the higher-order aberrations, by viewing the fitting glasses of the respective set one at a time whereby the strength of that lens with which it can best be seen determines the strength for correction of constitutes the specific higher order aberration for that eye.

The set of fitting glasses for correcting the eye defect coma can be built up by creating a set of fitting glasses with a positive cylindrical value in the upper half of the fitting glass and a negative cylindrical value in the lower half of the fitting glass, whereby the different fitting glasses have the the upper strength and the lower strength by 0.25 dpt.

The set of fitting glasses for correcting the spherical aberration can be built up by creating fitting glasses with a central negative power that is less negative or positive in power radially towards the periphery, or by creating fitting glasses with a central positive power that is less positive or negative in strength radially towards the periphery, with the central strength and the peripheral strength increasing by 0.25 dpt for the different glasses.

The set of fitting glasses for correcting secondary astigmatism can be built up by creating fitting glasses with a rotationally symmetrical strength pattern centrally within a zone of 2 mm: in the horizontal direction the glass has a strength of S- 0.25 dpt and in the vertical direction the glass has a strength of S+0.25 dpt, in the periphery this glass has a more positive strength in the horizontal direction compared to the central strength in the same direction and in the vertical direction a more negative strength compared to the central strength in the same direction, with the central strength increasing by 0.25 dpt for the different glasses.

The set of fitting glasses for correcting trefoil can be built up by creating fitting glasses that have negative power in three directions and positive power in three directions, with zones of 30 degrees distributed over a circle formed with an alternating a negative and a positive strength and between these zones there are gaps of 30 degrees in which the strengths of the neighboring zones gradually merge, and in which the positive and negative zones increase by 0.25 dpt for the different fitting glasses.

Detailed description of embodiments

When manufacturing a pair of contact lenses for improving visual performance in patients with keratoconus, it is first determined which eye of the patient has the least degree of keratoconus and thus is the best eye. Then, first for the best eye and then for the other eye (this order is preferred but not necessary), the following steps are taken: determining by subjective refraction the most effective conventional contact lens, with equal spherical and cylindrical power throughout the anterior optic zone, for that eye while the other eye is sufficiently nebulized or occluded, whereby the anterior optic zone of this contact lens forms a first optical zone. This is done by successively holding spherical fitting lenses of different strength in front of each eye to determine the base strength (of the first optical zone) of the contact lenses to be manufactured, the best base strength being the strength of the fitting lens with which with that eye can be seen the best, determining by subjective refraction optimal optical parameters for a second optical zone applied to the first optical zone, wherein the patient does not have to hold his/her head in a specific position, which optical parameters are formed by the shape, size, value and course of the strength and position on the first optical zone, manufacturing a fitting lens provided with a first and second optical zone as determined above, and repeating the determination of optimum optical parameters for the second optical zone by means of subjective refraction with the fitted lens inserted, and producing an adapted fitting lens when deviating optical parameters are found.

Then, one of the fabricated fitting contact lenses is inserted into each eye and, with both eyes watching, repeat the subjective refraction determination of optimal optical parameters for the second optical zones for each eye.

Thereafter, a set of final contact lenses having a first and second optical zone as determined above is manufactured.

The 1st OZ or the 2nd OZ of the contact lens can then be varied in light transmittance, where there is also the possibility to vary the diameter of the filter in the zone of the OZ.

Below, two embodiments of the method described above are described in detail.

Embodiment example 1 : A second optical zone is added to the front of a contact lens

On the front of a hard or thick soft contact lens, a second, decentered optical zone (2nd OZ) is added to the usual FOZ (1st OZ). This 2nd OZ has the following possibility of variation:

The optical structure

The diameter

The centering relative to the location of the 1st OZ The 1st or 2nd OZ is provided with a filter. The 2nd OZ is made of a contact lens material of a different refractive index.

The modified contact lens should preferably be rotation stabilized. Technically, all rotation- stabilized hard and thick soft contact lenses are suitable for this.

When a soft contact lens for keratoconus is made so thick that it assumes a spherical or toric surface on the front of the eye, this soft contact lens, like a hard contact lens, can be provided with a 2nd optical zone with a more positive power. All options for adjusting the optical zone, such as with a hard contact lens of the invention, also apply to the thick soft contact lens.

The optical structure:

1. Single In Strength:

The strength of the 2nd OZ is related to the 1st OZ and is more positive in strength than the 1st OZ. The strength of the 2nd OZ is described as an addition related to the 1st OZ. This addition can be varied in any desired strength.

The above effect can also be obtained by manufacturing the 2nd OZ from contact lens material with a different refractive index. The desired additions can be obtained by increasing or decreasing the refractive index of the contact lens material for the 2nd OZ relative to the desired measurement result.

2. Variable of Strength:

The strength of the 2nd OZ has the highest value centrally. This central value is related to the strength of the 1st OZ and is more positive in strength. If this strength development is expressed in an addition value, the central addition decreases radially towards the edge of the 2nd OZ. The addition can proceed as follows:

The centrally chosen addition decreases towards the edge to the strength equal to the 1st OZ

The centrally chosen addition slopes towards the edge and still has a more positive strength at the edge than the 1st OZ

The centrally chosen addition slopes towards the edge and has a more negative strength at the edge than the 1st OZ

The central addition can proceed smoothly in the 2nd OZ or in zones of decreasing strength. 3. Variable of Strength:

The strength of the 2nd OZ has the lowest value centrally. This peripheral value is related to the strength of the 1st OZ and is more positive in strength. If this strength development is expressed in an addition value, the peripheral addition decreases radially towards the center of the 2nd OZ. The addition can proceed as follows:

The peripherally chosen addition decreases towards the center to the strength equal to the 1st OZ

The peripherally chosen addition slopes towards the center and centrally still has a more positive strength than the 1st OZ

The peripherally chosen strength decreases towards the center and has a more negative strength centrally than the 1st OZ

The peripheral addition can proceed smoothly in the 2nd OZ or in zones of decreasing strength.

4. Descending Strength:

The 2nd OZ has the highest value at the top. This highest value is related to the strength of the 1st OZ and is more positive in strength than the 1st OZ. If this strength development is expressed in an addition value, the addition decreases more slowly from the top in the 2nd OZ to the bottom in the 2nd OZ. The addition can proceed as follows:

The chosen addition at the top of the 2nd OZ decreases downwards to an equal strength of the 1st OZ

The chosen strength at the top of the 2nd OZ tapers down and still has a more positive strength at the edge than the 1st OZ

The chosen strength at the top of the 2nd OZ slopes downwards and has a more negative strength at the edge than the 1st OZ

The addition may proceed from top to bottom, smoothly or in zones of decreasing strength.

The diameter of the 2nd OZ: The 2nd OZ can be adjusted in diameter. The diameter can be varied in all of the above optical construction variations. The diameter can be varied continuously from 0.5 mm - 15 mm.

The centering relative to the 1st OZ:

The centering of the 2nd OZ can be infinitely varied from 0.1 mm - 8 mm relative to the center of the 1st OZ.

The centering of the 2nd OZ can be infinitely varied from 0.1 - 8 mm relative to the horizontal position of the 1st OZ.

The 1st OZ as a filter:

The 1st OZ of the contact lens is designed as a filter. The filter is realized by massively coloring the material or by applying a filter on or in the material. All possible color filters can be selected for this. The filter can be selected by:

The percentage of light transmittance in the 1st OZ and ranging in diameter from 1mm - 15mm in the 2nd OZ and in diameter ranging from 0.5mm - 15mm

The 2nd OZ as a filter:

The 2nd OZ of the contact lens is designed as a filter. The filter is realized by massively coloring the material or by applying a filter on or in the material. All possible color filters can be selected for this. The filter can be selected by:

The initiation of keratoconus correction begins with the fitting of a stabilized, optically conventional contact lens.

The measurement starts in monocular, for which the other eye is sufficiently obscured. A high contrast test is started in the eye with the lowest degree of keratoconus. During this measurement, the subject does not have to specifically adjust the head position.

The adjuster determines, based on the subjective and objective results obtained, which type of optical structure and addition and addition pattern, which diameter of the 2nd OZ and what percentage of light transmittance of the filter is chosen.

The measurement is repeated in the same way with a fitting lens from the invention, the parameters of which are chosen such that they are expected to improve the measurement results. If the subjective result on the high contrast test is still unsatisfactory, this operation can be repeated again.

The use of keratoconus lenses from the patent of Frambach BV can provide insight into the choice of changes in the variations of the 2nd OZ of the passet of the invention to be selected. During the measurement with the keratoconus spectacle lenses from the patent of Frambach BV, the head position of the test subject will be an indication of the degree of change of the parameters to be selected.

With separate filter glasses, it can be tested whether the light transmittance of the filter in one of the contact lenses should be used or omitted, or whether it should be increased or decreased in light transmittance. The keratoconus lenses of the patent of Frambach B V can also be fitted with filters for this purpose.

The measurement is concluded by adjusting the parameters during a binocular measurement.

The objective and subjective measurement results on high and low contrast, under monocular and binocular conditions, can be used to determine the success of applying the selected parameters in the contact lenses of the invention.

Embodiment Example 2: Improved optics of an intraocular lens (IOL) for the correction of keratoconus.

Keratoconus is a progressive condition that develops in young people. Keratoconus causes a typical eye defect, which consists largely of higher order aberrations (HOAs). Only mild forms of keratoconus can be corrected sufficiently effectively in some cases with spherical and cylindrical prescription glasses. Keratoconus develops in young people who have relatively large pupil diameters. With large pupils, the amount of HOAs increases and visual performance decreases. Uncorrected HOAs negatively affect contrast sensitivity.

Corneal Cross-linking is a surgical procedure on the cornea, which strengthens the cornea; this can prevent further progression. Keratoconus is best corrected with hard contact lenses, for which you can choose from different lens types. Contact lens intolerance to hard contact lenses causes visual difficulties in functioning in daily activities. Temporary contact lens intolerance is common in keratoconus during seasonal episodes of allergic reactions. However, the visual performance of soft contact lenses, which can also be performed with aberration correction, is less effective than hard contact lenses and the correction of this type of contact lens is adversely affected by the necessary dexterity for a good fit.

The optical eye defect of keratoconus can also be corrected surgically with corneal intra-stromal rings. There are also technical possibilities to correct the eye defect of keratoconus with refractive surgery after stabilization of the cornea with corneal cross-linking (CXL). The thinness and associated instability of the cornea in keratoconus make the results of surgical procedures undesirable, uncertain or undone. This makes it better to have the option of optical correction for keratoconus with an IOL.

Many different types of IOLS have been developed for cataract surgery. Intraocular lenses can be used to replace your own eye lens. The optics of an IOL are able to correct spherical and cylindrical powers and to a limited extent a certain amount of spherical aberration (to better correct an eye without a ceratoconus. Various solutions have also been devised to prevent presbyopic complaints. There are also IOLs that stabilized elsewhere in the eye, for which various possibilities have been developed.

The effectiveness of contemporary IOLs for a keratoconus patient is limited to the correction of the spherical and cylindrical eye defect.

Due to risks of contact lens intolerance, visual performance for correction of keratoconus is not guaranteed. A surgical solution with an IOL specifically designed for the correction of keratoconus could optically overcome this problem, after which visual performance is assured if the keratoconus is stable. Such a solution is currently not available.

Optical Problems Of Keratoconus:

Because the pupil size varies much more in young people than in older people, visual performance varies greatly under different circumstances. A large pupil diameter develops in low light conditions, increasing the amount of HOAs from keratoconus. Visual problems are caused by a combination of a decrease in the contrast sensitivity of the eye and the lower contrast environment. Due to the ectasia in the cornea, the density of the cornea at that location decreases. Decreasing the density increases the amount of stray light, which is particularly detrimental to the contrast sensitivity.

Keratoconus can often be insufficiently corrected with spherical and cylindrical strengths. A hard contact lens addresses the optical problem where the problem originates. An IOL will have to have an optically very complex structure to be sufficiently effective to meet the visual needs of the keratoconus patient.

Keratoconus causes difficult-to-correct LOAs, HOAs and glare, often deficient in visual performance without contact lens correction. Large pupil diameters in young keratoconus patients cause greater amounts of HOAs that are unfavorable for visual performance under mesopic conditions. Stray light nuisance reduces the contrast, which in combination with HOAs can lead to dangerous situations not only during the day, but especially in the evening in traffic. Contact lenses cannot always be worn due to moments of intolerance due to the atopic complaints. The invention provides a solution for surgically restoring the visual performance of keratoconus patients, as an alternative or supplement to contact lenses.

A second, decentered optical zone of more negative power (2nd OZ) is added to the optics of an IOL. This 2nd OZ has the following possibility of variation: the optical structure the diameter the centering relative to the 1st OZ

A second more negative power is added to the optic of the spherical or toric IOL, in the form of a quadrant or a 2nd FOZ whose angle can be varied. This quadrant or 2nd FOZ has the following possibility of variation:

The chosen angle ranges from 5 to 180 degrees

The inclination varies from the horizontal from 1 to 180 degrees

The height of the segment varies from the center of the IOL

The 1st or 2nd OZ is provided with a filter.

A pin hole can be added to the optic of the IOL, whose outer rim diameter can be varied. The central clear part of the pin hole can also be varied in diameter.

Such an IOL can be provided with the correct position and inclination in the eye using all available techniques. The optical structure:

1. S ingle In S trength :

The strength of the 2nd OZ is related to the 1st OZ and is more negative in strength than the 1st OZ. The strength of the 2nd OZ is related to the 1st OZ as an addition. This addition can be varied to obtain the required vergence.

2. Single In Strength:

The strength of the quadrant or 2nd FOZ is related to the 1st OZ and is more negative in strength than the 1st OZ. The strength of the quadrant or 2nd FOZ is related to the 1st OZ as an addition. The quadrant or 2nd FOZ can be varied in angular degrees to obtain the required vergence.

3. Variable of Strength:

The strength of the 2nd OZ has the highest negative value centrally. This central value is related to the strength of the 1st OZ and is more negative in strength. In negative, if this strength development is expressed in an addition value, the central addition tapers off radially towards the edge of the 2nd OZ. The addition can proceed as follows:

The centrally chosen addition slopes towards the edge and still has a more negative strength at the edge than the 1st OZ

The centrally chosen addition slopes towards the edge and has a more positive strength at the edge than the 1st OZ

The central addition can be built up smoothly in the 2nd OZ or in zones with decreasing strength.

4. Variable of Strength:

The strength of the quadrant has the highest value at the top of the segment. The highest value is related to the strength of the 1st OZ and is more negative in strength. If this strength development is expressed in an addition value, the central addition to the base of the quadrant decreases more slowly. The addition can proceed as follows:

The chosen addition in the top of the quadrant decreases towards the base to the strength equal to the 1st OZ The chosen addition slopes towards the base and still has a more negative strength at the edge than the 1st OZ

The chosen addition slopes towards the base and has a more positive strength at the edge than the 1st OZ

The diameter of the 2nd OZ:

The 2nd OZ can be adjusted in diameter. The diameter can be varied in all of the above optical construction variations. The diameter can be varied continuously.

The centering relative to the 1st OZ:

The centering of the 2nd OZ can be varied steplessly relative to the center of the 1st OZ.

The centering of the 2nd OZ can be varied steplessly with respect to the horizontal position of the 1st OZ.

1. The 1st OZ as a filter:

The 1st OZ of the IOL is implemented as a filter. The filter is realized by massively coloring the material and possibly combining it with a polarized filter, or providing it with photochromatic properties. The filter can be selected by:

The percentage of light transmittance. the 1st OZ can be varied in diameter the 2nd OZ can be varied in diameter

2. The 2nd OZ as a filter:

The 2nd OZ of the IOL is implemented as a filter. The filter is realized by massively coloring the material and possibly combining it with a polarized filter, or providing it with photochromatic properties. The filter can be selected by:

The percentage of light transmittance the 1st OZ can be varied in diameter the 2nd OZ can be varied in diameter

Determining the IOL values for the correction of keratoconus Introduction:

To determine the strength of an IOL for patients with keratoconus, subjective refraction still seems to be the best method. Subjective refraction takes into account the adaptive capacity of the patient at the monocular and binocular level. A preoperative lens test provides the best estimate of satisfaction with subjective visual performance.

The eye defect of patients with keratoconus consists of lower-order aberrations and higher-order aberrations. The lower order aberrations can be corrected with spherical and cylindrical lenses. However, these rotationally symmetrical lenses are often insufficiently corrective to restore the visual performance of keratoconus patients. The higher-order aberrations of keratoconus patients that most affect visual performance can be divided into coma, spherical aberration, secondary astigmatism and trefoil. As with the correction of lower order aberrations using spherical and cylindrical lenses in ascending negative and positive power, a set of lenses can also be assembled to correct the higher order aberrations.

A slide that corrects the eye defect coma can be constructed optically as follows: The glass is built up by having a positive cylindrical value above the horizontal center.

The glass is built up because it has a negative cylindrical strength below the horizontal center.

For example, a passet of coma glasses can be constructed as follows:

The pass glass has a strength of blank = C+1.00 as 90 dpt on the top and a strength of blank = C-l .00 as 90 dpt on the bottom.

The axis direction can be determined with a KC glass, which is known in use by the skilled person.

The distribution of the cylinder strength can be determined with a KC glass, as the skilled person does in ordinary subjective refraction. For example, the cylinder strength at the top and bottom of the horizontal line can be determined differently, (for example, blank = C+1.00 axis 90 above and blank = C-7.00 axis 90 below). The patient looks for the best vantage point.

A passet of coma lenses can be created by increasing the power per 0.25 dpt, which allows the optometrist to systematically correct the eye defect of keratoconus similar to cylindrical lenses. In case of a sufficiently subjective result, in addition to a vision test, a contrast test can also be administered to examine the visual performance of the correction achieved.

If the result is insufficient, a set of lenses to correct the spherical aberration can be combined with the spherical, cylindrical and coma lenses.

A slide to correct spherical aberration is constructed as follows:

A slide for correcting spherical negative aberration has a negative power centrally that is less negative in power radially towards the periphery.

The slide has a strength of S-3.00 dpt centrally and slopes radially to the periphery to a less negative strength. It is also possible to reduce this strength radially to the periphery to a positive strength. In this way, the amount of spherical aberration induced by the slide can increase or decrease.

The central strength and the peripheral strength can be changed by 0.25 dpt.

Also, the pass glass centrally can have a positive strength that extends radially to the periphery to a more negative strength.

For example, a pair of lenses for the correction of negative and positive spherical aberration can be formed, with which the optometrist can systematically correct the eye defect of keratoconus, similar to spherical lenses.

In case of a sufficiently subjective result, in addition to a vision test, a contrast test can also be administered to examine the visual performance of the correction achieved.

If the result is insufficient, a set of lenses to correct secondary astigmatism can be combined with the spherical, cylindrical, coma and spherical aberration lenses.

A slide for correction of secondary astigmatism is constructed as follows:

A pass glass has a rotationally symmetrical strength pattern centrally within a zone of 2 mm: in the horizontal direction the glass has a strength of S-0.25 dpt and in the vertical direction the glass has a strength of S+0.25 dpt . This strength development is comparable to a cylindrical spectacle lens. In the periphery, however, this glass changes in the horizontal direction to a more positive strength relative to the central strength in the same direction. For example, on a slide that has a strength of S- 0.25 dpt in the horizontal direction, the strength in the periphery changes to a strength of S+0.75. With a glass that has a strength of S+0.25 dpt in the vertical direction, the strength in the periphery then changes to a strength of S-0.75.

For example, a passet with lenses for the correction of secondary astigmatism can increase per 0.25 dpt, with which the optometrist can systematically correct the eye defect of keratoconus, comparable to cylindrical lenses.

The strength development in the periphery can be selected as desired. A strength difference of three times the central value is described above, but it could just as easily be two times the value or four times the value.

If the result is unsatisfactory, a passet of lenses to correct for trefoil can be combined with the spherical, cylindrical, coma, spherical aberration and secondary astigmatism.

A trefoil correction slide is constructed as follows:

A slide has a negative strength in three directions. The negative strengths are of the size of 30 degrees and are distributed over a circle with 30 degrees spacing. This slide has a positive strength in three directions. The positive strengths are about 30 degrees and are distributed over a circle between the spaces of the negative strengths. The negative strength gradually blends into the positive strength and the positive strength gradually blends into the negative strength.

The first slide has 3 negative wedges with a strength of S-0.25 dpt, while the glass also has 3 positive wedges with a strength of S+0.25 dpt.

For example, a passet with lenses to correct for trefoil can increase per 0.25 dpt, so that the optometrist can systematically use the eye error of keratoconus, similar to a spherical and cylindrical glass, to correct the eye error.

Combining spherical and cylindrical lenses with lenses to correct for coma, spherical aberration, secondary astigmatism and trefoil will lead to the best visual performance achievable. It is not necessary to use all lenses in the correction. Improving subjective visual performance or vision will lead to the use of the particular slide in the overall recipe of the glass to be assembled. Just as separate spherical and cylindrical lenses are formed into one lens, a combination of the above lenses can also lead to one lens with the specific values used in the fitting glasses to achieve the best visual performance.

A spectacle lens as described above need not necessarily be designed as such in its entirety. For example, the spectacle lens can have the optical structure described in the center, but only spherical and cylindrical values in the periphery. The best vantage point is sought by the patient in situations where it is of value to better perceive details.

Above is described the subjective method by which the best visual performance is achieved with a specially developed lens. When the visual performance of the keratoconus patient is good with this correction, the correct IOL values can be calculated.

Because the prescription for spectacles is made up of different optical components, it is possible to calculate an IOL strength that achieves comparable results to correction of the above-mentioned composite spectacle lens.

The method of first testing a keratoconus lens and only then proceeding to correction with an IOL is a safer method than calculating and fitting the IOL directly. The prescription for glasses can easily be adjusted to the complaints that have not been solved with the correction. Correction of an implanted IOL requires a new operation, which poses risks to eye health.

The figures show four examples of a glass, where:

Figure 1 is an example of a glass with spherical aberration;

Figure 2 is an example of a Trefoil glass;

Figure 3 is an example of a glass with coma;

Figure 4 is an example of a lens that can correct secondary astigmatism.

Claims

CLAIMS:

1. A method of manufacturing lenses for improving visual performance in patients with keratoconus, comprising: for each eye: determining by subjective refraction the most effective conventional lens for that eye while covering or obscuring the other eye, the anterior optical zone of this lens forming a first optical zone of the lenses to be manufactured, determining by means of subjective refraction optimal optical parameters of a second optical zone of the lenses to be manufactured, which optical parameters comprise the sphero-cylindrical power, and manufacturing a set of lenses provided with a first and second optical zone arranged thereon as determined above, characterized in that the method further comprises the following steps: repeat the determination of optimal optical parameters for the second optical zone by means of subjective refraction for each of the two eyes with the lens inserted or in front of it, and if deviating optical parameters are found, manufacture an adapted lens, inserting in each eye or holding in front of each eye the fabricated or modified lenses and repeating with both eyes the determination by subjective refraction of optimal optical parameters for the second optical zones for each eye, and if deviating optical parameters are found, the manufacture of one or two adapted lenses if no adapted lenses have yet been manufactured for the manufactured lenses, or the manufacture of one or two further adapted lenses if adapted lenses have already been manufactured for the manufactured lenses, wherein in determining optimum optical parameters by subjective refraction, in addition to the strength of the optical zones and the position of the second optical zone on the first optical zone, furthermore the shape, size and variation of the strength of the second optical zone is determined, whereby the patient does not have to hold his/her head in a specific position during the determination of the optimal optical parameters, and where the anterior surface of the second optical zone is applied to the anterior surface of the first optical zone.

2. Method according to claim 1, for manufacturing a set of intraocular lenses, characterized in that: first the cornea of each eye of the patient is measured topographically, then the contact lenses manufactured in claim 1 are placed on the eyes of the patient, then the front of the contact lenses on the eyes is measured topographically, and finally, from the difference between the power map of the topographical image of the front of the contact lens and that of the cornea, a power map of an intraocular lens to be manufactured is determined, and on the basis of this a set of intraocular lenses is manufactured.

3. Method according to claim 1 or 2, characterized in that a pin hole is added to the optimum parameters depending on the visual performance.

4. Method according to Claim 1, 2 or 3, characterized in that a filter is arranged in the first and/or second optical zone, depending on the visual performance.

5. A method for determining the power of a lens for the correction of keratoconus, comprising: determining the power of a spherical and a cylindrical lens for correcting lower order aberrations using a set of spherical and a set of cylindrical fitting lenses of increasing prescription by visualizing the fitting lenses of each set one by one where the strength of that glass with which it can be seen best forms the strength for correction of lower order aberrations for that eye, and then determining the power of one or more spectacle lenses for correcting one or more of the higher order aberrations: coma, spherical aberration, secondary astigmatism and trefoil; using one or more sets of fitting glasses for each of the higher-order aberrations, by viewing the fitting glasses of the respective set one at a time whereby the strength of that lens with which it can best be seen constitutes the strength for correction of the specific higher order aberration for that eye.

6. Method according to claim 5, characterized in that the set of fitting glasses for correcting the eye defect coma can be constructed by creating a set of fitting glasses having a positive cylindrical value in the upper half of the fitting glass and a negative cylindrical value in the lower half of the fitting glass, whereby for the different fitting glasses the upper strength and the lower strength increase by 0.25 dpt.

7. Method according to claim 5 or 6, characterized in that the set of fitting glasses for correcting the spherical aberration can be built up by creating fitting glasses with a central negative power which radially towards the periphery is less negative or positive in power, or by creating fitting glasses with a positive power in the center that are less positive or negative in power radially towards the periphery, whereby the central power and the peripheral power increase by 0.25 dpt for the different glasses.

8. Method according to claim 5, 6 or 7, characterized in that the set of fitting glasses for correcting secondary astigmatism can be constructed by creating fitting glasses with centrally within a zone of 2 mm a rotationally symmetrical pattern of strength: in the horizontal direction the glass has a strength of S-0.25 dpt and in the vertical direction the glass has a strength of S+0.25 dpt, in the periphery this glass has a more positive strength in the horizontal direction compared to the central strength in the same direction and in the vertical direction a more negative strength with respect to the central strength in the same direction, with the central strength increasing by 0.25 dpt for the different glasses.

9. Method according to claim 5, 6, 7 or 8, characterized in that the set of fitting glasses for correcting trefoil can be constructed by creating fitting glasses having negative power in three directions and positive power in three directions, wherein divided over a circle, zones of the size of 30 degrees are formed with an alternating negative and positive strength, and between these zones there are interstices of 30 degrees in which the strengths of the neighboring zones gradually merge into each other, and in which the different fitting glasses have the positive and negative zones increase by 0.25 dpt.