Method of corneal analysis using a checkered placido apparatus

• US 6,450,641 B2
• Filed: 04/09/2001
• Issued: 09/17/2002
• Est. Priority Date: 06/02/1992
• Status: Expired due to Fees

• Current Assignee: Lasersight Technologies Inc. (Xianding Weng)
• Original Assignee: Lasersight Technologies Inc. (Xianding Weng)
• Inventors: Wakil, Youssef S., Sarver, Edwin J., DʼSouza, Henry M.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US09/828,148
• Publication Number:
  US 20010055095A1
• Time in Patent Office: 526 Days
• Field of Search: 351/200, 351/205, 351/206, 351/211, 351/212, 351/221, 351/246, 351/247, 356/124, 606/4, 606/5
• US Class Current: 351/212
• CPC Class Codes: A61B 3/107 for determining the shape or measuring the curvature of the cornea
• CPC Class Codes: G01B 11/255 for measuring radius of curvature measuring diameter G01B11/08

Abstract

A method for analysis of the curvature of the surface of a cornea using a checkered placido comprises, projecting the image of the checkered placido onto a patient'"'"'s cornea, detecting the image of the checkered placido reflected off of the cornea, detecting a plurality of nodal points from the reflected image, determining the mean curvature at a plurality of nodal points and analyzing the mean curvature at a plurality of nodal points in order to produce a graphic display of the estimated actual curvature of the cornea.

Claims

1. A method of corneal analysis using a webbed placido comprising:

projecting an image of a spider-webbed placido onto a cornea;

detecting a reflected image of said spider-webbed placido reflected off of said cornea;

detecting a plurality of nodal points from said reflected image of said spider-webbed placido;

determining a plurality of surface normals to a surface of said cornea at corresponding ones of said plurality of nodal points; and

analyzing said plurality of surface normals to estimate an actual curvature of said cornea.

2. The method of corneal analysis using a webbed placido according to claim 1, further comprising:

using said plurality of surface normals to determine a plurality of planes which define a multi-faceted surface area that is indicative of a radius of curvature of said cornea.

3. The method of corneal analysis using a webbed placido according to claim 2, further comprising:

smoothing said multi-faceted surface to represent an actual contour of said cornea.

4. The method of corneal analysis using a webbed placido according to claim 3, further comprising:

determining a mean curvature at a point where said actual curvature is known.

5. The method of corneal analysis using a webbed placido according to claim 4, wherein:

said point is determined from said step of analyzing said plurality of surface normals.

6. The method of corneal analysis using a webbed placido according to claim 3, wherein said smoothing comprises:

an integration of said multi-faceted surface.

7. The method of corneal analysis using a webbed placido according to claim 1, further comprising:

producing a graphical display of said estimated actual curvature of said cornea.

8. Apparatus for analyzing a cornea, comprising:

means for projecting an image of a webbed placido onto a cornea;

means for detecting a reflected image of said webbed placido reflected off of said cornea;

means for determining a plurality of nodal points from said detected, reflected of said webbed placido;

means for determining a plurality of surface normals to a surface of said cornea at corresponding ones of said plurality of nodal points; and

means for analyzing said plurality of surface normals to estimate an actual curvature of said cornea.

9. The apparatus for analyzing a cornea according to claim 8, further comprising:

a display to show said estimated actual curvature of said cornea.

10. The apparatus for analyzing a cornea according to claim 8, wherein:

said webbed image of said placido is a spider-webbed image.

11. The apparatus for analyzing a cornea according to claim 10, further comprising:

a display to show said estimated actual curvature of said cornea.

12. The apparatus for analyzing a cornea according to claim 8, wherein:

said webbed image of said placido is a spider-webbed image.

13. The apparatus for analyzing a cornea according to claim 8, further comprising:

means for using said plurality of surface normals to determine a plurality of planes which define a multi-faceted surface area that is indicative of a radius of curvature of said cornea.

14. The apparatus for analyzing a cornea according to claim 10, further comprising:

means for smoothing said multi-faceted surface to represent an actual contour of said cornea.

15. The apparatus for analyzing a cornea according to claim 14, further comprising:

means for determining a mean curvature at a point where said actual curvature is known.

16. The apparatus for analyzing a cornea according to claim 15, wherein:

said means for analyzing determines said point.

17. The apparatus for analyzing a cornea according to claim 14, wherein said means for smoothing comprises:

means for integrating said multi-faceted surface.

18. Apparatus for analyzing a cornea, comprising:

a webbed placido image to be projected onto a cornea;

a detector to detect a reflected image of said webbed placido reflected off of said cornea; and

a processor adapted to estimate an actual curvature of said cornea form a plurality of normals to a surface of said cornea at corresponding ones of a plurality of nodal points determined form said detected, reflected image of said webbed placido.

19. The apparatus for analyzing a cornea according to claim 18, wherein;

said processor is further adapted to use said plurality of surface normals to determine a plurality of planes which define a multi-faceted surface area that is indicative of a radius of curvature of said cornea.

20. The apparatus for analyzing a cornea according to claim 19, wherein:

said processor is further adapted to determine a mean curvature at a point where said actual curvature is known.

21. The apparatus for analyzing a cornea according to claim 19, wherein:

said processor integrates said multi-faceted surface to accomplish said smoothing.

22. The apparatus for analyzing a cornea according to claim 18, wherein:

said processor is further adapted to smooth said multi-faceted surface to represent an actual contour of said cornea.