EP2391260A1

EP2391260A1 - Model eye for calibrating an optical measurement system or a treatment laser system

Info

Publication number: EP2391260A1
Application number: EP10706166A
Authority: EP
Inventors: Gerhard Youssefi; Birgit Lutzenberger; Julia Hoff; Hans-Joachim Polland
Original assignee: Bausch and Lomb Inc
Current assignee: Bausch and Lomb Inc
Priority date: 2009-01-27
Filing date: 2010-01-26
Publication date: 2011-12-07
Also published as: WO2010086304A1; DE102009006306A1

Abstract

The invention relates to a device for calibrating or evaluating the performance of a refractive platform, which comprises a model eye and at least one reference element. According to an aspect of the invention the reference element comprises features for identifying the calibration device, when being used in an optical measurement system and/or a treatment laser system.

Description

MODEL EYE FOR CALIBRATING AN OPTICAL MEASUREMENT SYSTEM OR A TREATMENT LASER SYSTEM

Field of the Invention

The present invention relates to the field of ophthalmic diagnostic and treatment systems. It particularly relates to a device for calibrating an optical measurement system and/or a treatment laser system or for evaluating the performance of an optical measurement system and/or a treatment laser system. The invention further relates to a method for calibrating an optical measurement system and/or a treatment laser system or evaluating the performance of an optical measurement system and/or a treatment laser system using a platform calibration device. Moreover, the present invention relates to a method for manufacturing a calibration device.

Background of the Invention

WO 02/053021 A2 relates to a lens-eye model and method for predicting in-vivo lens performance of a vision altering optic. An eye model system includes a representative cornea, a dispersion medium, and a retinal surface. The corneal surfaces provide anatomical shape, optical power, and higher order aberration content. The dispersion medium mimics chromatic dispersion in an actual eye. The retinal surface is moveable to provide selected defocus. A method is described for remotely measuring the performance of a vision altering optic to predict its performance in-vivo including making topography, wavefront, interferometry, point spread function (PSF), modulation transfer function (MTF), or other optical and/or physical measurements of the model eye system with and without the optic in combination. A variety of vision altering optics can be used in combination with a model eye system such as contact lenses, IOLs, spectacle lenses, representative crystalline lenses, inlays and onlays. WO 03/049606 A2 relates to a model eye and aberrometer calibration method. More specifically, a model eye is used as a calibration component for use in calibrating and certifying the accuracy of an ophthalmic wavefront sensor. The calibration component comprises a monolithic, plano-convex refractive optic having known amounts of one or more selected aberrations induced by the spherical, axisymmetric aspherical, or non-axisymmetric aspherical convex surface. Further described is an alignment tool along with a procedure for calibrating an aberrometer. According to an embodiment, a series of model eyes can be used for evaluating a performance of an aberrometer.

US 2008/0144035 Al relates to an optical system calibration system and a method which is particularly suited for calibrating the optical slit planes in an ophthalmic diagnostic instrument. The calibration component includes at least two separated, diffusely reflecting surfaces. Images of an exemplary slit illumination pattern projected onto the calibration component and formed on the diffusely reflecting surfaces are detected by the image receiver such as a video camera. Based upon camera image coordinates and triangulation parameters of the projector, the receiver, and the calibration component, the slit image positions on the image detector plane can be calibrated to the axially displaced, diffusely reflecting calibration component surface positions. According to an embodiment, the calibration component consists of three stacked/fused glass plates wherein each plate includes an optically diffuse front surface whereupon the diffusely scattered illumination images are formed.

Summary of the Invention

It is an object of the invention to provide a device for calibrating or evaluating the performance of an optical measurement system and/or a treatment laser system and a method for calibrating or evaluating the performance of such systems and a method for manufacturing such a device for use in a platform comprising a plurality of different systems.

This object is achieved by the features of the claims.

According to an aspect of the invention, a device for calibrating or evaluating the performance of a refractive platform comprises a model eye and at least one reference element. According to an aspect of the invention the reference element comprises features for identifying the calibration device, when being used in an optical measurement system and/or a treatment laser system.

The reference element can be a part of the model eye. Thus, the model eye comprises within its optical path the features for identifying the calibration device, i.e., the type of calibration device and/or the individual calibration device. These identifying features may be realised as an iris structure having a unique iris code. The iris code may contain data for identifying the calibration device.

According to an embodiment the reference element is a removable insert such that the model eye may be combined with different inserts, wherein said inserts may have different features and functions as described below. The insert may be made of a light-transmissive material, for example glass or plastic. The features may be printed on the insert or otherwise inscribed thereon or within the material.

According to an aspect of the invention, the reference element or the insert may comprise an iris model, which in an example comprises gray scale structures. The iris model may comprise constant landmarks such as artificial iris structures. The iris model may be used for online and/or static landmark tracking and/or for lateral and rotational eye tracking. The artificial iris structures may be similar or identical to iris structures of a real eye. As an example, the iris structure may be printed on a plate-like element. The plate-like element is transmissive for light whereas the artificial iris structure is not transmissive for light.

According to a further aspect of the invention, the reference element or insert may comprise a pupil model, wherein the pupil model comprises a pupil having a predetermined position and a predetermined pupil size similar to a real eye corresponding to a respective light condition from bright light to dark light. In other words, the pupil size may correspond to a real eye having an undilated pupil and a real eye having a dilated pupil. Furthermore, the pupil model may comprise a pupil which is off-axis with reference to the symmetry axis of the device, i.e., corresponding to a decentred pupil of a real eye. The pupil model may be used for lateral eye tracking. This pupil model may be realised by using a light-transmissive plate-like element wherein the structures of a pupil are printed on a surface thereof.

According to a further aspect, the insert may comprise a light-absorbing surface. Such a light- absorbing surface may be realised by using a plate-like element which is not transmissive to light or which substantially absorbs all light falling on the plate-like element or light which goes through the plate-like element.

The device may receive one or more inserts. If two or more inserts are combined with the model eye, the inserts may be stacked one on the other.

According to an exemplary embodiment, a reference element or an insert may combine an iris model and a pupil model. The iris model may comprise an iris structure having a unique iris code. The iris code may contain data specific for the calibration device or the insert. These data may comprise information describing the pupil size of the reference element or the insert and/or the position of the pupil for example decentration amplitude and direction. The insert may be realised by printing on a light-transmissive plate-like element artificial iris structures and the structures of a pupil. For printing the structures, any type of ink may be used or any other means to provide structures similar to the iris structures and a pupil of a real eye. Thus, the ink may have different colours and different optical characteristics.

According to an alternative aspect, the artificial iris structures and the pupil may be realised in a different manner, e.g., the insert may have other forms different from a plate. Moreover, other techniques for darkening or colouring the surface of the insert or the material of the insert may be used for preparing the above-described insert.

According to an aspect of the invention, the model eye comprises a slit, which is substantially arranged along a cross-section with reference to an optical axis of the device. The optical axis of the device is defined as the axis along which light may travel through the model eye from a front surface to a back surface of the device and reflected light may travel from the back surface to the front surface of the device. Thus, the slit is provided in the beam path of light travelling through the model eye such that an insert can be placed therein. The combination of the model eye with the insert represents a calibration device according to the present invention. According to an exemplary embodiment, the device further comprises a slider received within the slit which is moveable between an open position and a closed position. Said slider preferably comprises a holder for holding the insert in a predetermined position.

According to a further aspect of the invention, the insert can be positioned with respect to the model eye in one of a plurality of different angular positions. For example, a square-shaped plate-like element may be placed in the slider in one of four different orientations with respect to the model eye. Alternatively, a plate-like element having the form of an octagon may be positioned in eight different orientations within the slider. According to a further alternative, a circular plate-like element may be positioned in any arbitrary angular position within a respective structure of a slider. As will become clear from the below further discussion, this possibility to change the orientation of the insert with reference to the model eye provides the advantage that a rotation of the eye may be simulated and corresponding calibration of an optical measurement system and/or a treatment laser system may be performed with reference to predetermined rotation angles.

Further features of exemplary embodiments of a calibration device will become apparent from the below discussion of the invention.

Another embodiment of the invention is directed to a method for calibrating or evaluating the performance of an optical measurement system and/or a treatment laser system. This method makes use of a platform calibration device which is used for calibrating one or several optical measurement systems and one or several treatment laser systems so that a unitary calibration of the whole platform can be achieved. Moreover, the same platform calibration device can be used for evaluating the performance of the optical measurement systems and the treatment laser systems of the platform. With a calibration device according to the present invention, various devices and systems in the same platform can be calibrated and the performance of all these devices and systems can be evaluated from time to time, e.g., according to a predefined time schedule like certain inspection intervals, which may be counted in days, weeks or months. Alternatively, a calibration device may be used for each individual patient, for whom one or both eyes are analysed using one or several optical measurement systems and treatment is performed using one or several treatment laser systems. Within the concept of the present invention, a system is considered to be an autonomously operating entity such as a wavefront sensor, a topographer or a laser. Rather than using several system calibration tools for each of these systems the present invention is based on the concept of using a single platform calibration device. This has the following advantage. When using a system calibration tool, each of the systems will be calibrated within its own specifications. Thus, where a platform consists of a set of diagnostic systems like wavefront measurement system, topography system, biometry system or others and at least one laser, like an excimer laser, femtosecond laser or others, the complete platform calibration may not be achieved. This might be the case where each of the systems is within the specified calibration range, but just at a very outer limit so that a propagation of individual errors may add up to an error which is outside an acceptance criteria. Another case which represents such a scenario may be subject alignment. If a diagnostic device measures a typical ophthalmic property such as topography, the data are represented within the coordinate system of the diagnostic device. For example, the axis of the astigmatism is expressed in degrees between 0° and 180° respective to the diagnostic 0° axis. Even if the therapy system, i.e., a laser system, may have the capability of analysing the orientation, for example by using the iris information, it is not implicitly given that all cameras and raw data acquisition tools are aligned. A misalignment of the cameras in one or both systems (diagnostic system and laser system) might lead to a mistreatment.

A platform calibration and evaluation of the performance can be achieved by using a platform calibration device as defined. The platform calibration device may comprise one or several inserts when performing calibration or evaluation of the performance of each of the optical measurement systems and the treatment laser systems.

A further embodiment of the invention is directed to a method for manufacturing a calibration device. This method comprises the following steps:

Providing a cap comprising a first anterior surface, arranging a globular segment having a substantially plano-convex shape at the cap such that a posterior surface of the cap is located at the convex shaped side and the transition between said cap and the globular segment providing a second anterior surface, arranging a body at the plane side of said globular segment, arranging a backside layer at said body opposite to said globular segment for scattering incident light. The globular segment is by way of example a spherical segment or by way of another example a half-sphere. It may also be any part which has on one side a convex surface and on the opposite side a substantially plane surface.

According to an aspect of the invention, the reference element is provided between the globular segment and the body. In an exemplary embodiment the reference element is an integral part of the globular segment or the body. The features for identifying the calibration device will be directly provided on the surface of the body or preferably the plane surface of the globular segment by, e.g., printing. Similarly, the iris model and/or the pupil model may be directly provided on the surface of the body and the plane surface of the globular segment, respectively.

According to an alternative aspect, a slit is provided between the globular segment and the body. The slit is adapted to receive an insert as described herein.

According to an aspect of the invention, a cap is separately formed on the globular segment by different techniques. In one exemplary embodiment, an evaporator evaporates material on one surface of the globular segment so that a layer is provided on the globular segment. Alternatively, a plasma coater comprising at least one evaporating source is used. Two evaporating sources may be used when the first source contains a substantially transparent material and a second source contains an impurity. The amount of the impurity within the manufactured cap can be controlled by controlling the temperatures of the two evaporation sources.

According to another aspect, the cap may be manufactured by mixing a first material of a two- component glue with an impurity to get a predetermined concentration of impurities in mixing the mixture with a second part of the two-component glue and providing this mixture on one surface of a globular segment and hardening this two-component glue.

By using the before discussed techniques or any other technique, a thin film of material comprising an initial level of impurity can be provided as a cap which is attached to the convex surface of the globular segment.

The foregoing and other objects, features and advantages of the embodiments of the present invention will be apparent from the following detailed description of the embodiments, which make reference to the several drawing figures.

Brief Description of the Drawings

Figure 1 shows the cross-section of an embodiment of a calibration device according to the present invention, and

Figure 2 shows a molding apparatus for manufacturing a calibration device according to the present invention.

Figure 1 shows an embodiment of a calibration device according to the present invention which can be used in an optical measurement system or a treatment laser system of a platform. This calibration device combines a model eye with an insert (not shown). Such a calibration device will generally comprise different layers of at least two different materials. In the embodiment as shown in Figure 1 , three different materials having corresponding different refractive indexes are present. More specifically, the calibration device 1 comprises in this order a cap 3, a globular segment 5, a slit 7, a body 9 and a scatter layer 11. The globular segment may also have the form of a spherical segment or of a half-sphere. The cap which is made of material 1 having a refractive index n_l is arranged on the convex surface of the globular segment 5. Thus, the cap has an anterior surface with a predetermined outer convex shape. The posterior surface of the cap is arranged at the convex-shaped side of the globular segment. The transition between said cap and said globular segment provides a second anterior surface. Adjacent to the plane side of the globular segment, the slit 7 is provided. The slit is adapted to receive an insert like a plate-like element comprising an iris model and/or a pupil model. The globular segment is made of a material 2 having a refractive index n_2. Opposite to the plane side of the globular segment, the body 9 made of material 3 and having a refractive index n_3 is arranged. At the distal end of the body 9, a scattering layer 11 is provided. The calibration device shown in Figure 1 preferably has a round, more preferably a circular cross-section. This calibration device may be used in a diagnostic or treatment system at a position where a patient's eye is located during diagnosis or treatment. Thus, the anterior surface of cap 3 corresponds to the outer surface of a cornea of a patient's eye.

Depending on the used optical measurement system, the optical properties of the calibration device can be determined similar to a patient's eye. For example, light which is reflected from the anterior surface of the cap enables the measurement of the elevation, curvature and online anterior shape during a shape-changing procedure.

The second anterior surface between the cap 3 and the globular segment 5 will also reflect light during such measurements. The reflection depends on the difference in refractive index between both materials of the cap and the globular segment, respectively. The light signals from the first anterior surface and the second anterior surface enables the measurement of the thickness of the layer of material 1 for example by OCT measurements (OCT - Optical

Coherence Tomography). This measurement can be performed before and after the shape changing procedure. Furthermore, an online thickness measurement of material 1 can be performed during a shape changing procedure. The anterior surface of the cap may comprise hydrophilic or hydrophobic coatings. Moreover, the anterior surface may comprise several coatings with different materials to mime organic layers such as collagen etc. Alternatively, a contact lens may be positioned on the anterior surface of the cap. The material of the cap may have a similar ablation characteristic as the cornea of a patient's eye when being treated with an excimer laser.

The cap itself is made of a material which is nearly transparent for the light used in the optical measurement system or the treatment laser system. The cap preferably contains impurities of a predetermined size and having predetermined optical properties. The size of the impurities and the optical properties of the impurities, in particular the absorptive characteristics of the impurities define the angular scattering properties of the light, e.g., whether it is close to Lambertian or far away. The concentration of the impurities defines the degree of scattering and the total absorption of the light by the cap. As shown in Figure 1, the thickness of the cap is dependent on its position, e.g., in the center position the thickness is larger than at the rim of the cap. In an alternative embodiment, the thickness of a cap may be constant. The globular segment 5 in the present embodiment of Figure 1 has a plano-convex shape. It may consist of a solid material which is nearby transparent for the light used in the system with a defined convex surface opposite to a plane side. This globular segment may have a similar topography like the cornea of a patient's eye.

The slit is adapted to receive an insert. More specifically, the slit may comprise a slider which is rαoveable within the slit between an open position and a closed position. The slider is adapted to receive the insert which may be a plate-like element. This arrangement provides the opportunity to use the calibration device with different inserts. For example, an insert having an iris image with artificial iris structures may be used. Such a calibration device can be particularly used to test online or static landmark tracking, in particular lateral eye tracking and rotational eye tracking within an optical measurement system or a treatment laser system.

Alternatively, an insert having a pupil structure may be used. Then the calibration device can be used for testing the function of optical measurement systems and treatment laser systems, especially the performance of any lateral eye tracking means.

In a further alternative embodiment the insert may be a plate-like element having an absorbing surface. In that case, the absorbing surface will avoid backscattering from the scattering layer 11 during specific diagnostic measurements. In the shown embodiment the size of the slit can be adjusted mechanically with the option to close the gap between the globular segment 5 and the body 9 completely. Alternatively, the size or width of the slit is adjusted to the thickness of the plate-like element, i.e., the thickness of the insert or the thickness of the number of inserts stacked one on the other.

The body 9 of the calibration device may be made of the same material as the globular segment 5 or the cap 3, alternatively the body may be made of a different material, different from materials 1 and 2 of the cap and the globular segment. Light which is focussed onto the back surface of the calibration device serves as a point source of beams which propagates through the whole setup and therefore the light contains information about the shape of all surfaces. The outgoing light can be analysed by, e.g., a wavefront measurement device. This enables wavefront measurements and online wavefront measurements of the calibration device. The scattering layer 11 on the backside of body 9 is designed to scatter the light in a similar way as the retina of a patient's eye.

The cap 3 can be manufactured in many sophisticated ways. In the first approach the cap could be evaporated with an evaporator or plasma coater with two different evaporating sources where the first source contains the basic transparent material like plastic and the second source contains the impurity.

The percentage of the impurity could be controlled by the temperatures of the evaporation sources, e.g., if the source with the impurity material is relatively cold a resulting cap would have weak level of impurity whereas a higher temperature would lead to a higher percentage of the impurity and hence to higher light scattering of the cap.

In another implementation of this invention the cap 3 could be made of a thin film of material which has the initial level of impurity. The film could be glued to the globular surface of the base material (globular segment) or stick to it by cohesive forces.

Another implementation is realised by coloured contact lenses which are put onto the globular surface of the base material (globular segment) similar to the application of a contact lens on the cornea of the eye.

hi another implementation of this invention the cap could be made of two component glue which becomes rapidly solid after reunion of the two parts. One part of the glue could be first mixed with the impurity to get the right concentration of impurities. After mixing of the two components the mixture becomes rapidly solid.

According to an alternative embodiment the cap is fabricated by injection moulding. Part of the mould could be the basic material whereas for the other surface another mould is used. Figure 2 shows a suitable moulding apparatus.

The moulding apparatus comprises a cylinder 201 which receives at one end the basic material 109 which later forms the body. At one side of the basic material 109 a globular segment 105 is arranged. Opposite to the convex surface of the globular segment 105 a second mould 202 is positioned within the cylinder 201. The second mould 202 comprises a channel 204 or hole through which material can be provided to the cavity between the convex shape of the globular segment 105 and the concave shape opposite thereto of the second mould 202. The complete system is heated to a temperature well below the melting point of all components 109, 201 and 202 but above that of a plastic for the cap. For forming the cap 103 the fluid plastic with a defined concentration of impurities is filled into the space between the globular segment 105 and the second mould 202 through the channel 204.

After cooling the complete system and removing the second mould 202 and the cylinder 201 this calibration device should be ready. As an option the cap of the artificial model eye could be manipulated by means of laser ablation and/or mechanical milling.

The above described calibration device can be used as a platform calibration device in a method for calibrating or evaluating the performance of an optical measurement system and/or a treatment laser system. An exemplary method comprises the following steps. The platform calibration device will be positioned along an optical axis of the optical measurement system and/or the treatment laser system. Then the optical measurement system and/or the treatment laser system will perform a measurement using the respective procedures as when measuring a patient's eye. Then the measurement data will be compared with pre-stored data corresponding to the platform calibration device which is used in this method. Alternatively, the data regarding the used platform calibration device can directly be obtained from the information of the reference element or the insert. More specifically, an iris code may comprise data regarding the specific platform calibration device, e.g., information regarding the identification of the calibration device, information regarding the position of the calibration device as well as information regarding the pupil size and the position of the pupil with reference to a symmetry axis of the device, hi a further step the result of this comparison will be used for calibrating and/or evaluating the performance of the optical measurement system and/or the treatment laser system.

When using a calibration device which comprises means for receiving an insert, in particular a slit, wherein an insert may be placed, the following additional step will be present in the method. Before positioning the platform calibration device or after positioning the platform calibration device along an optical axis of the optical measurement system and/or the treatment laser system, an insert is placed preferably in a determined orientation in the calibration device. Then the before mentioned steps for the measurement, the comparison and calibration and/or evaluation the performance are performed. The method can be repeated by using a different insert in the calibration device or by placing the same insert in a different orientation in the calibration device.

Furthermore, according to an aspect of the present invention, a set of different calibration devices having different optical characteristics can be used in combination with one or several inserts among a plurality of different types of inserts.

It will be appreciated that while the foregoing is a full and complete description of the preferred embodiments of the invention, various modifications, alternate constructions and equivalence will occur to those skilled in the art. Thus, the foregoing description should not be construed as limiting the invention, which is defined by the appended claims.

Claims

1. A device for calibrating an or evaluating the performance of an optical measurement system and/or a treatment laser system, said device comprising a model eye and at least one reference element.

2. The device of claim 1, wherein the reference element is an insert being removable from the model eye.

3. The device of claim 1 or 2, wherein the reference element or the insert comprises features for identifying the calibration device and/or the insert.

4. The device of any of claims 1 to 3, wherein said reference element or insert comprises an iris model preferably comprising gray scale structures, preferably for online and/or static landmark tracking and/or for lateral eye tracking, preferably for rotational eye tracking and/or for identifying the calibration device.

5. The device of any of claims 1 to 4, wherein said reference element or insert comprises a pupil model comprising a pupil having a predetermined pupil size, said pupil being preferably decentred with reference to a symmetry axis of the device for lateral eye tracking.

6. The device of any of claims 1 to 5, wherein said insert comprises a light absorbing surface.

7. The device of any of claims 1 to 6, wherein said model eye comprises a slit for receiving said insert and preferably further comprising a slider being movable within the slit between an open position and a closed position.

8. The device of any of claims 1 to 7, wherein said insert comprises a plate-like element, wherein said plate-like element provides the iris model and/or the pupil model and the light absorbing surface, respectively.

9. The device of any of the preceding claims, wherein the model eye comprises in the following order:

- a cap comprising a first anterior surface,

- a globular segment having a substantially plano-convex shape, wherein said cap is arranged with its posterior surface at the convex shaped side and the transition between said cap and the globular segment provides a second anterior surface, - a body arranged at the plane side of said globular segment, and

- a backside layer arranged at said body opposite to said globular segment for scattering incident light.

10. The device of claim 9, wherein the reference element is provided between the globular segment and the body.

11. The device of claim 9, wherein a slit is arranged between the globular segment and the body and wherein the slit preferably has a variable size.

12. The device of any of claims 9 to 11, wherein the first anterior surface of the cap is a coating or a contact lens.

13. The device of any of claims 9 to 12, wherein the thickness of the cap is constant or varies depending on the location.

14. The device of any of claims 9 to 13, wherein the first surface of the cap comprises at least one material to mime organic layers, preferably such as collagen, and comprises hydrophilic or hydrophobic properties.

15. The device of any of claims 9 to 14, wherein the cap is made of a material which is substantially transparent for the used light, and wherein the cap preferably contains impurities with a predetermined size to define the angular scattering properties and a predetermined concentration of impurities to define the degree of scattering and the absorption of light.

16. The device of any of claims 9 to 15, wherein the globular segment comprises a solid material which is substantially transparent for the used light with a predetermined surface, preferably having a similar topography like a cornea of a human eye, wherein the topography of the half sphere preferably matches a typical topography of the posterior surface of the cornea.

17. A method for calibrating or evaluating the performance of an optical measurement system and/or a treatment laser system using a platform calibration device preferably according to any of claims 1 to 16, comprising the steps of: a) positioning the platform calibration device along an optical axis of the optical measurement system and/or the treatment laser system, b) performing a measurement with the optical measurement system and/or the treatment laser system, c) comparing measurement data of step b) with pre-stored data corresponding to the platform calibration device, d) calibrating and/or evaluating the performance of the optical measurement system and/or a treatment laser system based on the comparison result of step c).

18. The method of claim 17 comprising the further step of: placing an insert or another insert in the calibration device or placing the insert in a different orientation in the calibration device, and repeating steps b) to d).

19. The method of claim 17 or 18, wherein said reference element or said insert comprises an iris model, said iris model preferably comprises gray scale structures, the method further comprising the step of online and/or static landmark tracking and/or for lateral eye tracking, preferably for rotational eye tracking and/or for identifying the calibration device.

20. The method of any of claims 17 to 19, wherein said reference element or said insert comprises a pupil model comprising a pupil having a predetermined pupil size, said pupil being preferably decentred with reference to a symmetry axis of the device, the method further comprising the step of detecting the position of the pupil and/or for lateral eye tracking.

21. The method of claim 18, wherein said insert comprises a light absorbing surface.

22. The method of any of claims 17 to 21, wherein said calibration device comprises a model eye comprising a slit for receiving said insert and preferably further comprising the step of moving a slider within the slit between an open position and a closed position for placing said insert into the slider.

23. The method of any of claims 17 to 22, wherein said insert comprises a plate-like element, wherein said plate-like element provides the iris model and/or the pupil model and the light absorbing surface, respectively.

24. The method of claim 22 or 23 , wherein the model eye comprises in the following order: - a cap comprising a first anterior surface,

- a globular segment having a substantially plano-convex shape, wherein said cap is arranged with its posterior surface at the convex shaped side and the transition between said cap and the globular segment provides a second anterior surface,

- a body arranged at the plane side of said globular segment, and - a backside layer arranged at said body opposite to said globular segment for scattering incident light, wherein a reference element or a slit for receiving an insert is provided between the globular segment and the body.

25. The method of any of claims 17 to 24, wherein the step of performing a measurement comprises at least one of the following diagnostic measurements: performing a measurement of a curvature of the surfaces of the calibration device, preferably of the anterior and posterior surfaces of the cap, performing a measurement of an elevation data set of the calibration device, preferably of an elevation map of the cap portion of the calibration device, performing a measurement of a thickness of at least a part of the calibration device, using ultrasound, optical slit projection technology or partial coherence tomography and performing a wavefront measurement.

26. The method of any of claims 17 to 25, further comprising the step of performing a shape change using a treatment laser system for creating a desired optical effect.

27. The method of claim 26, further comprising the step of analysing the optical effect of a shape change using an optical measurement system during or after the step of performing a shape change.

28. The method of any of claims 17 to 27, further comprising checking and/or verifying alignment parameters in particular during a shape change procedure.

29. The method of any of claims 17 to 28, further comprising providing a set of different calibration devices having different optical characteristics, which are adapted to be combined with individual inserts among a plurality of different types of inserts.

30. Method for manufacturing a device for calibrating an optical measurement system and/or a treatment laser system comprising the following steps:

- providing a cap comprising a first anterior surface,

- arranging a globular segment having a substantially plano-convex shape at the cap such that a posterior surface of the cap is located at the convex shaped side and the transition between said cap and the globular segment providing a second anterior surface,

- arranging a body at the plane side of said globular segment, arranging a backside layer at said body opposite to said globular segment for scattering incident light, and - providing a reference element or a slit adapted to receive an insert between the globular segment and the body.

31. Method of claim 30, comprising the following steps for manufacturing the cap: evaporating material with an evaporator or a plasma coater comprising at least one evaporating source, preferably comprising two evaporating sources where the first source contains a substantially transparent material and a second source contains an impurity, and controlling the amount of the impurity by the controlling the temperatures of the evaporation sources.

32. Method of claim 30, comprising the following steps for manufacturing the cap: mixing a first material of a two-component glue with an impurity to get a predetermined concentration of impurities and mixing the mixture with a second part of the two-component glue.

33. Method of any of claims 30 to 32, comprising the following steps: providing a thin film of material comprising an initial level of impurity as said cap and attaching the thin film to the convex surface of the globular segment.