Patent EA-004236-B1 (EA)
Title: System and method for the non-contacting measurement of the axis length, and/or cornea curvature, and/or anterior chamber depth of the eye, preferably for intraocular lens calculation
Inventor: BARTH ROLAND
IPC: A61B3/15
Filed: 1999-12-10
Abstract: 1. Combined device for non-contacting determination of axial length (AL) and a radius of cornea curvature (14), having: a) interferometer system (1-6) with adjustable path length difference, b) first beam splitter cube (8) projecting radiation of interferometer system (14), c) photodiode (17) on which the light beam components reflected from cornea and retina are moving out, while measuring axial length through the second beam splitter cube (15) and focusing element (16), d) several concentrically and symmetrically arranged to the optic axis of the eye(14) light sources(10), each illuminating the eye on the angle to optic axis for measuring of cornea curvature, forming pixel pattern, and e) camera (23), on which the Purkinje images are projected while measuring the cornea curvature through the first and second beam splitter cubes(8, 15)representing the reflection of pixel light sources from cornea, f) part of radiation of interferometer system, reflected by cornea and retina, is projected for observation on the camera. 2. Combined device according to claim 1 wherein the camera is CCD -camera (23). 3. Combined device according to claim 1 or 2 comprising six concentrically and symmetrically arranged to the optic axis of the eye light sources light-emitting diodes (10), their radiation being collimated by image optics. 4. Combined device according to any of claims 1-3, comprising concentrically arranged to the optic axis of the eye light sources (24), forming on the cornea the projected on the camera pixel images to bring the eye (14) in required position, wherein said light sources serves simultaneously for illumination and for bringing the eye in required position. 5. Combined device according to any of claims 1-4, comprising a light source (1, 1a) serving for radiation input in interferometer, light source being provided for eye (14) fixing, wherein the photodiode perceives the light reflected from cornea when the eye (14) is placed exactly on the optic axis of combined device, and produces a continuous stress signal, the level of it serving as a criteria of precision of bringing the eye (14) in required position. 6. Combined device according to claim 4, wherein the light sources are infrared light-emitting diodes (24), which are placed annually in each case between the light sources (10), provided for measuring of the radius of cornea curvature. 7. Combined device according to any of claims 1-6, comprising a system for measuring anterior chamber depth (VKT) of the eye (14) with slit-shaped illumination source (12, 12a) radiated lateral to the eye at an angle via image optics. 8. Combined device according to claim 7, wherein imaging optics (13) is anamorphotic, preferably as a cylindrical optics, and is provided with light-emitting diode (12) and for slit diaphragm. 9. Combined device according to claim 7 or 8, wherein the light scattered by different layers of the eye (14) from slit-shaped illumination source (12, 12a) is detected on a camera of image optics (8, 15, 18, 19). 10. Combined device according to claim 9, in which said optics has first and second beam splitter cubes (8, 15) and achromatic lens (18, 19) and the scattered light is projected on camera used for measuring of radius of cornea curvature. 11. Combined device according to claim 9, in which telecentric diaphragm (21) being swiveled out and limiting the aperture to increase the accuracy of measurements before camera (23), and being swiveled out achromatic lens (22). 12. Combined device according to any of claims 1-11, comprising wherein a laser diode is provided to input the radiation in interferometer system (1-6). 13. Combined device according to claim 1 or 2, comprising quarter-wave plate (P1), placed between the first and the second beam splitter cubes (8, 15), both beam splitter cubes (8, 15) being made as polarizing light splitter. 14. Combined device according to any of claims 1-13 in combination with claim 7, having the controller (C) for controlling the measuring process, that operates with the camera (23) and several light sources while measuring the cornea curvature or with camera (23) and slit-shaped illumination source (12, 12a), turning on and turning off said light sources (10), correspondingly slit-shaped illumination source (12, 12a), camera (23) in synchronization with that process makes bright image at turned on light sources, correspondingly at turned on slit-shaped illumination source, and dark image -at turned off light sources, correspondingly at turned off slit-shaped illumination source. 15. Combined device according to any of claims 1-13, comprising the controller (C), realizing the central control of regulating by position elements and optic components of that device, and calculating the focal power of intraocular lens implanted into the eye. 16. Combined device according to claim 15, having a memory, in which the design formulas, called by corresponding request are stored. 17. Combined device according to claim 15 or 16, allowing to further determine the anterior chamber depth of the eye. 18. Combined device according to claim 17, which determines the axial length at the beginning, then radius of cornea curvature and after that anterior chamber depth, or at the beginning determines the radius of cornea curvature, and then axial length and after that anterior chamber depth of the eye. 19. Combined device for non-contacting determination of axial length and a radius of cornea curvature and/or anterior chamber depth of human eye, having the interferometer system (1-6) with adjustable optic path length difference and beam splitter cube (8, 15), having high transmission factor in visible and nearest infrared range of the specter and high reflection factor of linearly polarized radiation, coming from interferometer system as a laser radiation. 20. Combined device according to claim 19, in which beam splitter cube (8) has high transmission factor for the radiation reflected from the eye. 21. Combined device according to claim 19, in which beam splitter cube (8) has quarter-wave or half-wave plate. 22. Method of determining the radius of cornea curvature and/or anterior chamber depth of human eye using the device according to any of claims 2-18, characterized in that the eye is illuminated, important subimages are projected on CCD-camera, the illumination is turned on and off in a synchronized manner with video pulses of the CCD camera and every time at turned on illumination the light image is received using CCD-camera, and the dark image - when the illumination is off. 23. Method according to claim 22, in which at receiving of differential image for noise suppression the dark image is subtract from the light image in successive images, correspondingly frames. 24. Method according to claim 23 for determining the anterior chamber depth of the eye, characterized in that the eye is illuminated with slit image projected on it, the pupil and the fixation point in the pupil are detected in the dark image, the edge shape of the scatter images of the slit illumination is determined in the differential image, the distance X of the front edges of the cornea and lens scatter images, on the base of said distance X the anterior chamber depth is calculated.