Method of eye examination by optical coherence tomography
A method of performing an OCT image scan is presented. Other images are taken and a template is formed to correct the OCT images, for example, for eye motion, blood vessel placement, and center offset. In some embodiments, video images are taken simultaneously with the OCT images and utilized to correct the OCT images. In some embodiments, a template OCT image is formed prior to acquisition of the OCT images and the template OCT image is utilized as a template from which to correct all of the OCT images.
1. A method of eye examination, comprising:
acquiring OCT images corresponding to a scan pattern, wherein the scan pattern substantially covers a nerve head region;
the scan pattern includes a plurality of concentric circles and a plurality of radial lines intersecting at the center of the concentric circles and intersecting at least one of the concentric circles;
determining optical disk boundary points from the OCT images;
matching the optical disk boundary points with the optical disk boundary determined from one or more separate template images;
correcting the optical disk boundary points; and
determining at least one nerve head morphology characterization.
2. The method of claim 1 , wherein correcting the optical disk boundary points includes performing a blood vessel correction.
3. The method of claim 1 , wherein correcting the optical disk boundary points includes determining an optical disk center.
4. The method of claim 3 , wherein determining at least one nerve head morphology characterization includes determining retinal nerve fiber layer thickness in a circle centered on the optical disk center.
5. The method of claim 1 , wherein the one or more template images are video images taken simultaneously with the OCT images.
6. The method of claim 5 , wherein correcting the optical disk boundary points includes correcting for eye movement.
7. The method of claim 1 , wherein the one or more template images is a template OCT image taken with a raster scan pattern.
8. The method of claim 7 , wherein a nerve head boundary is determined in the template OCT image.
9. The method of claim 1 , wherein the scan pattern spans an area large enough to encompass the nerve head region.
10. The method of claim 1 , wherein a retinal nerve fiber layer thickness is calculated at a particular diameter circle centered on the nerve head.
11. The method of claim 5 , wherein the video images are acquired with near IR light.
12. The method of claim 5 , further including determining an optical disk boundary in each of the video images.
13. The method of claim 12 , wherein determining the optical disk boundary is performed automatically.
14. The method of claim 12 , wherein determining at least one of the optical disk boundaries is performed by an operator.
15. The method of claim 8 , wherein the nerve head boundary is determined by
forming an enface image from the template OCT image;
determining the boundary contour from the enface image.
16. The method of claim 1 , wherein one or more of the separate template images used corresponds to a 3D data set collected using a dense OCT raster scan comprising the optical nerve head region.
17. The method of claim 16 , wherein forming an enface image further comprises:
adding data from a plurality of layers at different depths in the three-dimensional OCT scan; and
adjusting the different layers used to form the enface image to find a close correlation between the nerve head boundary contour and the retinal pigment epithelial RPE tips found in the cross sectional images obtained from the OCT scans.
18. The method of claim 15 , wherein determining the boundary from the enface image further comprises:
saving the boundary contours as a baseline; and
using a cross correlation algorithm to register a new OCT scan with the enface image having a baseline boundary contour.