Topography module for ophthalmological devices with a distance-independent keratometer and method for the use thereof

Abstract

A module for ophthalmological devices which enables ophthalmological devices to carry out keratometry and topography measurements of the eye. The proposed topography module is provided for ophthalmological devices with a distance-independent keratometer. The topography module, which is used to generate the luminous pattern, is arranged in a fixed or moveable manner in the beam path between the ophthalmological device and the eye. A control unit is provided to control the topography module for generating luminous patterns. The provided evaluation unit is also suitable to carry out keratometric as well as topographic evaluations of the reflection images of an eye, captured and transmitted by the detection unit. The invention enables ophthalmological devices, which are equipped with a distance-independent keratometer, to carry out additional topographical measurements on the eye.

Claims

1. A topography module for ophthalmological devices that have a distance-independent keratometry measurement device having a detection beam path including including elements for distance independent keratometry measurement, elements for illumination and detection, as well as elements for control and evaluation, wherein: the topography module generates a luminous pattern, and the topography module is disposed, in a stationary or moveable manner, in a beam path between the ophthalmological device and the eye, wherein the topography module transmits a keratometry beam, and includes devices that facilitate placement of the topography module at a definite position in the beam path between the ophthalmological device and the eye, wherein an existing control unit of the ophthalmological device is adapted for controlling the topography module appropriately for generating light patterns, wherein an existing evaluation unit is suitable for evaluating the reflected images of an eye recorded and transmitted by the detection unit in both a keratometric as well as topographic manner; and wherein the topography module is transparent, and for generation of the light pattern necessary for topography measurements, has local light decoupling inhomogeneities in a volume thereof or structures on its surface, or an opto-electronic coating.

2. The topography module according to claim 1, wherein the detection beam path of the distance-independent keratometry measurement device is telecentric.

3. The topography module according to claim 1, wherein the topography module has a disk-shaped, planar, conical or similar form.

4. The topography module according to claim 1, further comprising rings, grids, points, bars that are used as the light pattern for topography measurements.

5. The topography module according to claim 1, further comprising a lighting unit that is disposed, for illumination of the local light decoupling inhomogeneities in its volume, or the structures on its surface, such that light is laterally introduced into a peripheral surface or surfaces of the topography module.

6. The topography module according to claim 5, wherein the lighting unit is composed of numerous light sources distributed over the circumference.

7. The topography module according to claim 1, wherein the local diffusing inhomogeneities in the volume thereof, or the structures in or on the surface thereof are disposed such that both the beams of the keratometer light sources as well as the telecentric detection beam path are not affected.

8. The topography module according to claim 1, further comprising a coating in the form of an OLED film that is used as the opto-electronic coating for generating the light pattern for topography measurements.

9. The topography module according to claim 8, wherein the OLED film is capable of depicting luminous light patterns through an appropriate activation by the control unit, such that there is no need for a lighting unit.

10. The topography module according to claim 9, wherein arbitrary dynamic light patterns can be depicted with the OLED film, depending on activation thereof, and wherein the light patterns can be varied in terms of color and contrast.

11. The topography module according to claim 9, wherein, in addition to the light patterns necessary for the topography measurement, additional light points for fixation can be depicted with the OLED film, depending on the activation thereof.

12. The topography module according to claim 1, further comprising appropriate coatings and/or covers for reducing effects of diffused light.

13. A method for keratometric and topographic measurement of a cornea of an eye using a topography module for ophthalmological devices, comprising: illuminating and detecting the eye distance-independently for a keratometric measurement, and positioning the topography module in a beam path; integrating the topography module into a control and evaluation logarithm of the ophthalmological devices; b) recording a second image, in which a fixation light and a light sources for the keratometric measurement are switched on, c) recording a third image, in which the fixation light and the light sources for the topographic measurement are switched on, and e) evaluating the recorded images, and outputting the results wherein, to determine the greatest possible consistency, first curvature radii at keratometric measurement points are compared with the second curvature radii determined based on the topographic data, at the keratometry measurement points and wherein the topographic data can be varied if necessary.

14. The method according to claim 13, further comprising: f) recording a first image, in which only the fixation light is switched on, g) recording a fourth image, in which the fixation light and an infrared lamp are switched on.

15. The method according to claim 14, wherein the steps a) to d) can be repeated numerous times, to obtain a greatest possible consistency between the topographic data and the keratometric data, and outputting a result thereof.

16. The method according to claim 13, wherein the steps b) and c) can be executed simultaneously.

17. The method according to claim 13, wherein the topographies are determined for different distances between the cornea and measurement device in order to vary the recording or recordings made in step c).

18. The method according to claim 13, wherein evaluation of the images recorded with keratometric lighting in step e) are based on a spherical model.

19. The method according to claim 13, wherein evaluation of the images recorded with topographic lighting in step e) are based on a toric model.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention shall be explained in greater detail below, based on exemplary embodiments. Therein:

(2) FIG. 1: depicts cross sections of disk-shaped, planar topography modules,

(3) FIG. 2: depicts the front views of two topography modules,

(4) FIG. 3: depicts a cross section of a topography module having an expanded measurement range,

(5) FIG. 4: depicts the fundamental construction of a 6 point keratometer with a topography module,

(6) FIG. 5: is a graph illustrating the dependency of the determined radius on the actual distance between the eye and the measurement device, and

(7) FIG. 6: is the schematic depiction of three variations of a scaled topography.

DETAILED DESCRIPTION

(8) The topography module according to example embodiments of the invention is intended for ophthalmological devices, which have a distance-independent keratometry measurement device with a detection beam path and the necessary units for this, for illumination, detection, as well as control and evaluation.

(9) In accordance with example embodiments of the invention, the topography module used for the generation of luminous patterns is disposed in a stationary or moveable manner in the beam path between the ophthalmological device and the eye, for which it has devices that ensure placement at a defined position in the beam path. The existing control unit is capable of controlling the topography module in order to generate the light patterns. Furthermore, the existing evaluation unit is suitable for evaluating the reflected images of an eye recorded and transmitted by the detection unit, both keratometrically as well as topographically.

(10) The topography module has a disk-shaped, planar, partially conical, or similar shape.

(11) Although for the topography module, a planar shape is preferred, at least in its center, it may have other geometries extending outward, such as a conical or similar shape, for example.

(12) According to a first design, the topography module is transparent and is composed of, for example, glass or plastic.

(13) In accordance with the invention, the topography module has local diffusing or reflecting inhomogeneities in its volume, or structures in or on its surface, or a luminous opto-electronic coating, for generating the light pattern necessary for the topography measurements. Typically, well known patterns, such as rings, grids, points, bars, etc. are used as the light pattern for topography measurement. Preferably, the sizes of the diffusing structures can be varied such that the generated patterns exhibit a uniform brightness or illumination level.

(14) In accordance with a first example design, a lighting unit is disposed on the topography module for illuminating the local diffusing inhomogeneities in its volume, or the structures on its surface, such that the light is introduced laterally into its peripheral surface(s).

(15) The light coupled via the peripheral surface(s) is conducted through total reflection over the entire disk cross section, and is diffused or decoupled at the inhomogeneities or structures, respectively, toward the eye.

(16) For this, FIG. 1 shows disk-shaped, planar topography modules in a cross section. While the topography module TM on the left-hand side has local diffusing inhomogeneities SS.sub.in in the interior of the disk volume, the topography module TM illustrated on the right-hand side has structures on its surface SS.sub.out. A number n of topography light sources TB.sub.n are disposed on the topography module TM for lighting the internal or external diffusing structures SS.sub.in or SS.sub.out, which represent the lighting unit as a whole. The light of the topography light sources TB.sub.n is introduced into the end surface of the topography module TM. The topography module TM for example has no diffusing structures surrounding the optical axis OA in the central region, because this region forms the telecentric detection beam path DS.sub.tz.

(17) As can be seen in FIG. 2, the lighting unit is composed of numerous lighting elements distributed over the circumference, for example in the form of light emitting diodes. The topography module does not necessarily have to have a rotationally symmetrical shape thereby.

(18) Furthermore, the local diffusing inhomogeneities in its volume, or the structures on its surface are disposed such that both the beams of the keratometer light sources as well as the telecentric detection beam path are not affected, or only to a slight extent.

(19) For this, FIG. 2 shows the front view of two topography modules TM with topography light sources TB distributed over the circumference thereof. The central region of the topography module TM is designed as an opening, or at least has no diffusing structures. As a result, it is ensured that the telecentric detection beam path DS.sub.tz is not affected by the local diffusing inhomogeneities SS.sub.in. By way of example, structures are shown here, which generate light patterns in the form of a ring system that is similar to that of a Placido disk. The effect on the beam paths for the keratometer light sources KB.sub.n can be prevented in different ways.

(20) The surface of the topography module TM in the upper drawing is divided from the inside toward the outside, such that following the telecentric detection beam path DS.sub.tz, there is a first region, which contains local diffusing inhomogeneities SS.sub.in for generating the light pattern for the topography measurement, a second region, provided for the keratometer light sources KB.sub.n, and a third region, which again contains local diffusing inhomogeneities SS.sub.in for generating the light pattern for the topography measurement.

(21) In contrast thereto, with the topography module TM in the lower drawing, the local diffusing inhomogeneities SS.sub.in are simply interrupted at the locations of the beam path for the keratometer light sources KB.sub.n. This may be necessary, in particular with an increasing density of the inhomogeneities SS.sub.in.

(22) In accordance with a second design, the topography module has an opto-electronic coating, with which the light pattern needed for the topography measurements is generated. Preferably, transparent OLED films are used thereby for the coating.

(23) By application of an appropriate electrical activation, the OLED film is capable of depicting luminous patterns, such that no additional lighting unit is needed. Arbitrary, static and dynamic light patterns can be depicted thereby, depending on the type and manner of activation, which can be varied in terms of color and contrast.

(24) Thus, the spacing and dimensions of the light structures can be adjusted in a variable manner. Each possible pattern structure can thus be generated: annular, punctiform, reticulate, or a combination thereof. The light pattern can for example be adapted to the anatomy as well as to the surface function that is to be optimized. A temporal adaptation of the structure formed during the measurement is also possible thereby. In this manner, the lighting structure can be adapted in an optimal manner to the individual anatomy of the eye that is to be measured. This is important for patients, in particular, whose corneas have scar tissue resulting from operations or accidents, which lead to strong distortions of the pattern projected onto the eye.

(25) This is because it is important, for the measurement of reflected patterns for determining the topography of an eye, that the respective light source can be assigned distinctly to each measurement point. This is difficult in particular with deformed, pathological anatomies, because an overlapping or overtaking of the image points may occur. In this context, OLED films furthermore offer the advantage that light structures can be generated, which can be varied in terms of the color, contrast or sequencing thereof. As a result, the measurement points can also be distinctly assigned to the relevant light sources in the case of strong distortions. With the use of OLED films of this type, there is also the possibility of being able to depict additional light points for fixation with the topography module, in addition to the light patterns necessary for the topography measurement.

(26) Another advantage can be seen in the flexibility of the OLED films. As a result, it is possible to realize non-planar geometries as well, in order to make optimal use of the available space in an ophthalmological device.

(27) A possible source of interference signals in the construction described above is diffused light, which is emitted from the topography disk toward the device. This light illuminates the surface of the device, and thus reduces the contrast between the diffusion structures and the background in the image.

(28) In accordance with an additional design aspect, the affect of this diffusion beam can be minimized through various approaches: in which the device housing located behind the topography module has a dark and/or matte surface, in which the diffusion structure is not located directly in front of the housing, and in which the topography module has appropriate coatings and/or coverings.

(29) The regions of the beam paths of the keratometer light sources as well as the telecentric detection beam path are, thereby, excluded from the coating. Optical openings that cannot reflect light already exist in ophthalmological devices.

(30) If different wavelengths are used for the keratometer and topography light sources, the coatings for reducing the diffused light effects are to be adapted accordingly.

(31) FIG. 3 depicts a topography module having an expanded measurement region, in a cross sectional view. The topography module TM here also has diffusing inhomogeneities SS.sub.in in the interior of the disk volume, for the illumination of which, a number n of topography light sources TB are disposed on the topography module TM, which represent the lighting unit as a whole.

(32) The central region of the topography module TM, which has a coplanar form herein, contains both the telecentric detection beam path DS.sub.tz as well as the region for the keratometry beams. As a result, a distortion of the keratometry beams can be prevented in the transmission, or at least minimized. A larger measurement region on the cornea can be covered by the conical region adjoining it at the periphery.

(33) FIG. 4 shows the fundamental construction of a 6 point keratometer having the topography module according to the invention.

(34) The 6 point keratometer K is composed thereby of the telecentric detection beam path DS.sub.tz, having an imaging lens AO, a telecentric aperture B.sub.T and an image sensor BS, as well as the beam paths KS.sub.n for the keratometer light sources KB.sub.n having a pinhole aperture B.sub.Ln and a plano-convex lens L.sub.PKn. The topography module TM, having the local diffusing inhomogeneities SS.sub.in and the topography light sources TB.sub.n is disposed between the eye A and the 6 point keratometer K, preferably directly in front of the 6 point keratometer.

(35) It can be seen in FIG. 4 that the topography module TM has no local diffusing inhomogeneities SS.sub.in in either the region of the telecentric detection beam path DS.sub.tz, or in the region of the beam paths KS.sub.n of the keratometry light sources KB.sub.n, that could affect them.

(36) The light sources KB.sub.n and TB.sub.n are preferably designed such that the emission of light occurs in the near infrared spectral range, in order to avoid interfering with the patient's ability to maintain a specific line of sight.

(37) Because the keratometry structures are projected onto the eye from the infinite, in general they will have a slightly different focusing plane in the imaging on the camera chip than the topography structure. This is caused by the reflected imaging on the cornea surface (or on the precorneal tear film). This difference can be compensated for when the two emission wavelengths differ from one another in a defined manner. In this case, the focusing planes are displaced against one another through the chromatic aberration of the imaging lens, and via an appropriate alignment of the two light source wavelengths and the imaging lens, the desired result can be obtained.

(38) It is particularly preferred therefore that the emission wavelengths are selected such that at an optimal measurement distance, both the keratometer as well as the topography structures are sharply focused on the camera sensor.

(39) In another design, the topography module is not transparent, wherein there are two variations for this.

(40) If the non-transparent topography module is to remain in the beam path, then corresponding openings are to be provided for the keratometer light sources, a potentially existing slit lamp, and the detection beam path. This results, however, in a reduction in the amount of available data.

(41) These openings are not necessary if the non-transparent topography module is subsequently inserted in the beam path, i.e. only for the topography measurement. This is possible using a fold-down or sliding mechanism. The consequences of this, however, are that the sequential measurements require substantially more time.

(42) In this variation it is even conceivable that the topography module is mechanically entirely separate, and can be attached to the ophthalmological device by means of magnets, for example. It should be noted, however, that a precisely reproducible positioning of the topography module in the measurement position is necessary, which can be ensured by means of appropriate stops or snap-in devices.

(43) Embodiments for non-transparent add-on modules of this type are well known to the person skilled in the art, from diverse commercial devices and patent applications, such that these are only mentioned here for the sake of completeness.

(44) For an exact determination of the topography of the cornea of an eye by use of individual light structures or Placido ring systems, it is absolutely necessary, due to the type of light source, to know or determine the distance between the eye, or cornea, respectively, and the measurement device.

(45) For this, FIG. 5 shows the effect of the actual distance between the eye and the measurement device for determining the radius based on a spherical model. The correct radius R.sub.Kugel of 8.35 mm is established at a measurement distance D.sub.m of 70 mm between the eye and the measurement device. With a deviation in the measurement distance D.sub.m of only 0.5 mm, the established radius R.sub.Kugel already deviates by more than 0.06 mm from the correct radius R.sub.Kugel.

(46) With the disclosed method, it is not necessary to determine the actual distance between the eye and the measurement device, because the established keratometric data are taken into account in the evaluation of the topographic data, and the distance is established indirectly thereby.

(47) The method according to example embodiments of the invention for the keratometric and topographic measurement of the cornea of an eye using a topography module for ophthalmological devices, in which the keratometric measurement of the eye is illuminated and detected in a distance-independent manner, and in which the topography module is positioned in the beam path in a first step, and is integrated into the control and evaluation logarithm, is characterized by the following steps: b) recording of a second image, in which the fixation light and the light sources for the keratometric measurement are switched on, c) recording of a third image, in which the fixation light and the light sources for the topographic measurement are switched on, e) evaluation of the recorded images and outputting the results.

(48) The keratometric and topographic measurement of the cornea of an eye in the proposed method can be improved even more by the following steps: a) recording of a first image, in which only the fixation light is switched on, and d) recording of a fourth image, in which the fixation light and an infrared lamp are switched on.

(49) In step a), the reflections striking the cornea from the surroundings are recorded under measurement conditions, i.e. when the eye is directed at the fixation light, in order to be able to eliminate them from the recordings in the evaluation. In contrast, the recordings made in step d) help in distinguishing the edge of the iris from the annular structures of the keratometer light sources.

(50) The measurement sequence for keratometry and topography for example occurs such that numerous recording cycles are carried out with this set sequence. In this case, the keratometry and topography measurements are to be regarded as simultaneous, and it is thus avoided that possible deviations need to be taken into account in calculating the consistency of the measurement data.

(51) In order to accelerate the method, steps b) and c) can be carried out simultaneously.

(52) In accordance with the invention, the steps a) to d) are repeated numerous times, in order to obtain the greatest possible consistency between the topographic data and the keratometric data, and to output this as the result. In order to determine the greatest possible consistency thereby, the curvature radii at the keratometric measurement points are compared with the curvature radii at these measurement points, established on the basis of the topographic data, and varied if necessary.

(53) The comparison, or a necessary variation, respectively, occurs thereby based on the images recorded in steps a) to c), as follows.

(54) The curvature radius R.sub.K of the cornea is absolutely precisely determined from the (keratometric) image recorded in step b). The topography of the cornea can be determined from the image recorded in step c), although its simulated curvature radius R.sub.T may not be correct, because the distance between the cornea and the measurement device is unknown.

(55) The curvature radii R.sub.K and R.sub.T are then compared. If both curvature radii are identical, or the deviation lies within an acceptable tolerance, then the results can be output in step e). Otherwise, in the evaluation of the topography data, they are varied until the curvature radii R.sub.K and R.sub.T are identical, or their deviation lies within an acceptable tolerance.

(56) For this, FIG. 6 shows a schematic depiction of three variations of a varied topography T.sub.1, T.sub.2, T.sub.3 with their curvature radii R.sub.T1, R.sub.T2, and R.sub.T3, as well as the curvature radius R.sub.K determined from the keratometric imaging based on a spherical model M.sub.K. It can be derived from FIG. 6 that the curvature radius R.sub.K most closely resembles the varied topography T.sub.2 having the curvature radius R.sub.T2.

(57) The variation occurs thereby, such that the topography for various (but not known) distances between the cornea and the measurement device are determined from the recording made in step c).

(58) The working distance, for example, for which diffusion structures are imaged in a normal eye at maximum sharpness on the image sensor, can be selected as the starting value.

(59) The variation can occur, for example, in that the topography are scaled accordingly, directly at the points of the keratometer measurement, or on a surface function fitted to the topography. This can be achieved with both radii data as well as gradient data.

(60) The evaluation of the images recorded with keratometric lighting according to step e) can be based thereby on a spherical model or a toric model.

(61) Fundamentally, it is also possible to use the proposed topography module for ophthalmological devices that also have a distance measurement device or a distance setting device. In this case, the evaluation of the topography data can occur without direct reference to the keratometry data.

(62) Here as well, however, the greatest possible consistency between the topographic data and the keratometric data is established, and this is output as the result. The necessarily present distance measurement device is used to indicate possible faulty measurements. If the deviations between the two measurement methods exceed an established tolerance, a warning message is issued. The measurement must then be repeated.

(63) A solution is provided with the present invention, which makes it possible for ophthalmological devices that have a distance-independent keratometry measurement device, to also implement topographic measurements on an eye, and this being without knowing or having to determine the distance between the cornea and the measurement device.

(64) The solution thus unites the advantages of keratometric and topographic measurements of an eye with limited technical expenditure. The present invention suitable both as an alternative add-on module, and also, with the appropriate adjustments, as a retrofitting module, for ophthalmological devices already in use. In particular, embodiments of the invention suitable for use in distance-independent 6 point keratometers.