Ophthalmologic visualization system

• US 20110019150A1
• Filed: 06/21/2010
• Published: 01/27/2011
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Carl Zeiss Meditec AG (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Meditec AG (Carl-Zeiss-Stiftung)
• Inventors: Meckes, Günter, Schuhrke, Thomas, Thornton, Keith, Gräber, Stefan
• Granted Patent: US 8,662,667 B2
• Time in Patent Office: Days
• US Class Current: 351/206
• CPC Class Codes: A61B 3/11 for measuring interpupillary distance or diameter of pupils
• CPC Class Codes: A61B 3/111 for measuring interpupillary distance
• CPC Class Codes: A61B 3/112 for measuring diameter of pupils
• CPC Class Codes: A61B 3/14 Arrangements specially adapted for eye photography apparatus or arrangements for taking photographs per se G03B
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

A method determines the position and/or radius of the limbus and/or the position and/or radius of the pupil of a patient eye. In the method, an image of the patient eye is obtained and a plurality of different ring-shaped comparison objects having respective radii and respective centers are provided. The image is correlated with the plurality of comparison objects to yield a local best match between the image and the comparison objects when there is a coincidence of one of the ring-shaped comparison objects and a ring-shaped jump in brightness in the image having the same radius and the same center. The comparison objects having a local best match with the image are determined. Thereafter, the position of the center of the comparison object having a local best match with the image is selected as the position of the center of the limbus and/or the position of the center of the pupil.

Claims

1. A method for determining the position and/or radius of the limbus and/or the position and/or radius of the pupil of a patient eye, the method comprising the steps of:

obtaining an image of the patient eye;

providing a plurality of different ring-shaped comparison objects having respective radii and respective centers;

correlating said image with said plurality of said comparison objects to yield a local best match between said image and said comparison objects when there is a coincidence of one of said ring-shaped comparison objects and a ring-shaped jump in brightness in said image having the same radius and the same center;

determining said comparison objects having a local best match with said image; and

,

selecting the position of the center of the comparison object having a local best match with said image as the position of the center of the limbus and/or the position of the center of the pupil.

2. The method of claim 1, wherein the radius of the comparison object having the local best match with said image is selected as the radius of the limbus and/or the radius of the pupil.

3. The method of claim 2, wherein the radii of said comparison objects are different.

4. The method of claim 3, wherein:

(a) the radius of that comparison object, which has the largest radius and has a local best match between said image and said comparison objects, is selected as the radius of the limbus; and

/or,

(b) the radius of the comparison object having the second largest radius and having the local best match between said image and the comparison object is selected as the radius of the pupil; and

/or,

(c) the center of the comparison object having the largest radius and having the local best match between said image and said comparison objects is selected as the position of the center of the limbus; and

/or,

(d) the center of the comparison object having the second largest radius and having the local best match between said image and said comparison objects is selected as the position of the center of the pupil.

5. The method of claim 1, wherein the radii of the ring-shaped comparison objects are the same.

6. The method of claim 1, wherein a red color component of a digital image of the patient eye, which corresponds to the red color channel, forms the basis of the correlation of the ring-shaped comparison objects with said image.

7. The method of claim 1, wherein one of said ring-shaped comparison objects comprises two concentric ring-shaped components.

8. The method of claim 1, wherein one of said ring-shaped comparison objects is configured as a polygon.

9. The method of claim 1, wherein one of said ring-shaped comparison objects comprises segments.

10. The method of claim 1, wherein one of said ring-shaped comparison objects is configured as a ring.

11. The method of claim 1, wherein one of said ring-shaped comparison objects is configured as a disc.

12. The method of claim 1, wherein one of said ring-shaped comparison objects is configured as a part ring.

13. The method of claim 12, wherein said image of said patient eye is a digital image having an edge region;

and, said digital image is correlated at said edge region with ring-shaped comparison objects configured as part rings.

14. The method of claim 1, wherein said ring-shaped comparison objects are closed ring filters or part ring filters;

and, a filter response (A) of said ring filters is computed for said image of the patient eye as a measure for the correlation of said image of the patient eye and said ring filters.

15. The method of claim 14, wherein each of said ring filters comprises an inner filter ring and an outer filter ring.

16. The method of claim 15, wherein the inner and the outer filter rings of said ring filter each contribute to said filter response with a different sign.

17. The method of claim 14, wherein a local maximum filter response (A) is determined with respect to said ring filters;

and, the position of the center and the radius of the ring filter, on which said filter response (A) is based, is selected as the position of the center of the limbus of the patient eye and as the radius of the limbus; and

/or, as the position of the center of the pupil of the patient eye and the radius of the pupil.

18. The method of claim 15, wherein the radius of said inner filter ring is smaller than the radius of the pupil of the patient eye and the radius of the outer filter ring is greater than the radius of the pupil of the patient eye;

or, the radius of the inner filter ring is smaller than the radius of the limbus of the patient eye and the radius of the outer filter ring is greater than the radius of the limbus of the patient eye.

19. The method of claim 17, wherein said filter response (A) is computed in a computer unit via a convolution of a digital image of the patient eye with a filter function for said ring filters;

and, said computer unit determines a filter function having at least one local maximum filter response from the computed filter responses.

20. The method of claim 19, wherein the radius of the ring filter having the local maximum filter response is selected as the radius of the pupil or the limbus of the patient eye;

and, the position of the center of said ring filter is selected as the position of the center of the pupil or of the limbus of the patient eye.

21. The method of claim 1, wherein a measure (A) for the correlation of said image of the patient eye and the ring-shaped comparison object, which has the local best match with the image of the patient eye, is compared to a measure for the correlation of a reference image having a ring-shaped comparison object.

22. The method of claim 20, wherein the ring-shaped comparison object is a ring filter;

and, the criterion for the local best match with the image of the patient eye is an at least local maximum filter response of the ring filter for the image of the patient eye and for the reference image.

23. The method of claim 22, wherein a quantity (Z) is generated as a measure for the reliability of a determined radius of the pupil and/or of the limbus of the patient eye and/or of a determined position of the center of the pupil and/or of the limbus of the patient eye from the deviation of the measure for the correlation of the image of the patient eye from the measure for the correlation of a reference image with the comparison object.

24. The method of claim 23, wherein said measure for the reliability is indicated by an indicator unit.

25. The method of claim 24, wherein the indication is effected acoustically or optically.

26. The method of claim 25, wherein the indication is reflected into the optical beam path.

27. The method of claim 1, wherein the method comprises the further steps of:

detecting a digital image of the patient eye;

convoluting the detected image of the patient eye with ring-shaped filters having mutually adjacent rings and the filters having different radii;

forming the difference of filter responses of two different mutually adjacent rings;

determining local maximum differences and the radii corresponding to the filters having these differences; and

,

determining a smaller of the determined radii as the radius of the pupil of the patient eye and/or the position of the center of the filter having a smaller determined radius as the position of the center of the pupil of the patient eye.

28. The method of claim 1, wherein the method comprises the further steps of:

detecting a digital image of the patient eye;

convoluting the detected image of the patient eye with ring-shaped filters having mutually adjacent rings and the filters having different radii;

forming the difference of filter responses of two different mutually adjacent rings;

determining local maximum differences and the radii corresponding to the filters having these differences; and

,

determining a larger of the determined radii as the radius of the limbus of the patient eye and/or the position of the center of the filter having the largest determined radius as the position of the center of the limbus of the patient eye.

29. The method of claim 1, wherein the method comprises the further steps of:

determining a favorable radius for the ring-shaped comparison objects; and

,

determining the position of the center of the limbus of the patient eye and/or the position of the center of the pupil of the patient eye by correlating sequentially detected digital images of the patient eye during an eye treatment with said favorable radius and ring-shaped comparison objects having different centers.

30. The method of claim 29, wherein a camera detects the digital images of the patient eye;

and, the favorable radius is automatically adjusted when there is a change in the recording mode of said camera.

31. The method of claim 29, wherein the favorable radius is the radius of a comparison object selected as the radius of the limbus or as the radius of the pupil of the patient eye.

32. A computer program for a method for determined the position of the limbus and/or the pupil of a patient eye according to claim 1.

33. An arrangement for determining the position and/or the radius of the limbus and/or of the pupil of a patient eye, the arrangement comprising:

a video camera for recording a digital image of at least one detail of a patient eye; and

,

a computer unit for holding a computer program of claim 32.

38. The system of claim 33, wherein the radii of the ring-shaped comparison objects are the same.

39. The system of claim 33, wherein a red color component of a digital image of the patient eye, which corresponds to the red color channel, forms the basis of the correlation of the ring-shaped comparison objects with said image.

40. The system of claim 33, wherein said ring-shaped comparison objects are closed ring filters or part ring filters;

said filter have an inner filter ring and an outer filter ring; and

, a measure for the correlation of the image of the patient eye and said comparison objects is determined by computing the filter response of a ring filter for the image of the patient eye.

41. The system of claim 39, wherein the inner and outer filter rings of said ring filter each contribute to said filter response with a different sign.

42. The system of claim 40, wherein a first measure (A) for the correlation of the image of the patient eye and of the comparison object in form of the ring filter having at least local maximum filter response is compared to a second measure for the correlation of a reference image and a comparison object in the form of a ring filter having an at least local maximum filter response;

a quantity (Z) is generated from the deviation of the first measure from the second measure with said quantity (Z) being a measure for the reliability of a determined radius of the pupil or of the limbus of the patient eye or a determined position of the center of the pupil or of the limbus of the patient eye; and

, said quantity (Z) is indicated by an indicating unit.

34. An opthalmologic visualization system for eye surgery, the system comprising:

an apparatus for determining the position and/or radius of the limbus and/or the position and/or radius of the pupil of a patient eye;

means for obtaining an image of the patient eye;

a plurality of different ring-shaped comparison objects having respective radii and respective centers;

means for correlating said image with said plurality of said comparison objects to yield a local best match between said image and said comparison objects when there is a coincidence of one of said ring-shaped comparison objects and a ring-shaped jump in brightness in said image having the same radius and the same center;

means for determining said comparison objects having a local best match with said image; and

,

means for selecting the position of the center of the comparison object having a local best match with said image as the position of the center of the limbus and/or the position of the center of the pupil.

35. The system of claim 34, wherein the radius of the comparison object having the local best match with said image is selected as the radius of the limbus and/or the radius of the pupil.

36. The system of claim 35, wherein the radii of said comparison objects are different.

37. The system of claim 36, wherein:

(a) the radius of that comparison object, which has the largest radius and has a local best match between said image and said comparison objects, is selected as the radius of the limbus; and

/or,

(b) the radius of the comparison object having the second largest radius and having the local best match between said image and the comparison object is selected as the radius of the pupil; and

/or,

(c) the center of the comparison object having the largest radius and having the local best match between said image and said comparison objects is selected as the position of the center of the limbus; and

/or,

(d) the center of the comparison object having the second largest radius and having the local best match between said image and said comparison objects is selected as the position of the center of the pupil.