Method for finding the lateral position of the fovea in an SDOCT image volume
Embodiments of the present invention provide methods for finding the lateral position of the fovea in an OCT image volume. In one instance, a cost function is developed whose minimum is located at or near the foveal center. This cost function includes one or more measures of retinal layer thickness and/or measures of distance from blood vessels or a priori locations.
1. A method of determining the location of the fovea within an image of an eye, said image being obtained with an optical coherence tomography (OCT) system, said OCT system including a light source generating a beam of light, a sample arm a reference arm and a detector for measuring light combined from the sample and reference arms, said method comprising the steps of:
scanning the beam of light over a region of the eye;
combining the light from the sample and reference arms;
measuring the combined light to generate three dimensional image information;
analyzing the image information to determine the location of the fovea within the image, said analyzing step being performed by segmenting the image information and assigning values across the image, said values corresponding to the integrated intensity as a function of depth, said segmenting being selected so that the integrated intensity reaches an extremum as the likelihood of that location being at or near the center of the fovea increases; and
storing or displaying the determined foveal location.
2. A method as recited in the claim 1 wherein the integrated intensity is evaluated in a region near the inner limiting membrane (ILM).
3. A method as recited in claim 1 wherein the determined foveal location is indicated by indicia on a display of the image information.
4. A method as recited in claim 1 further including the step of calculating thickness of the macular layer in the region of the determined foveal location.
5. A method as recited in claim 1 wherein the analyzing step further includes evaluating a second, different location dependent image quantity that reaches an extremum as the likelihood of that location being at or near the center of the fovea increases and wherein the results of the evaluations of the two different quantities are combined in order to determine the foveal location.
6. A method as recited in claim 5 wherein the second location dependent image quantity relates to the location of blood vessels in the image information.
7. A method as recited in claim 5 wherein the second location dependent image quantity relates to the lateral distance from the center of the scanned region in the plane of the scan.
8. A method as recited in claim 5 wherein the second location dependent image quantity relates to the distance from the inner limiting membrane (ILM) to inner plexiform layer (IPL).
9. A method as recited in claim 5 wherein the second location dependent image quantity relates to local curvature of the inner limiting membrane (ILM).
10. A method of determining the location of the fovea within an image of an eye, said image being obtained with an optical coherence tomography (OCT) system, said OCT system including a light source generating a beam of light, a sample arm a reference arm and a detector for measuring light combined from the sample and reference arms, said method comprising the steps of:
scanning the beam of light over a region of the eye;
combining the light from the sample and reference arms;
measuring the combined light to generate three dimensional image information;
segmenting the image information to isolate a region wherein the integrated intensity of the image information within the region reaches a minimum as the likelihood of that location being at or near the center of the fovea increases, said integrated intensity information being computed as a function of intensity information over depth;
analyzing the integrated intensity image information to determine the location where the intensity has reached a minimum; and
storing or displaying the determined foveal location.
11. A method as recited in claim 10 wherein the segmented region corresponds to a region beginning at the inner limiting membrane (ILM) and extending to a predetermined depth below the ILM.
12. A method as recited in claim 10 wherein the segmented region corresponds to a region beginning at the inner limiting membrane (ILM) and extending to a depth below the ILM, said depth being determined as a function of the distance from the ILM to the retinal pigment epithelium (RPE).
13. A method as recited in claim 10 wherein the analyzing step further includes evaluating a different location dependent image quantity that reaches an extremum as the likelihood of that location being at or near the center of the fovea increases and wherein the results of the evaluations of both the integrated intensity image information and the second quantity are combined in order to determine the foveal location.
14. A method as recited in claim 13 wherein the different quantity relates to the location of blood vessels in the image information.
15. A method as recited in claim 10 wherein the determined foveal location is indicated by indicia on a display of the image information.
16. A method as recited in claim 10 further including the step of calculating thickness of the macular layer in the region of the determined foveal location.
17. A method of determining the location of the fovea within an image of an eye, said image being obtained with an optical coherence tomography (OCT) system, said OCT system including a light source generating a beam of light, a sample arm a reference arm and a detector for measuring light combined from the sample and reference arms, said method comprising the steps of:
scanning the beam of light over a region of the eye;
combining the light from the sample and reference arms;
measuring the combined light to generate three dimensional image information;
analyzing the image information to determine the location of the fovea within the image, said analyzing step including evaluating a quantity associated with each of at least two different independent indicators of fovea location, said two different indicators being combined and weighted, wherein one of said indicators of foveal location relates to the level of integrated intensity across the image, said integrated intensity being measured as a function of depth; and
storing or displaying the determined foveal location.
18. A method as recited in claim 17 wherein the integrated intensity is evaluated in a region near inner limiting membrane (ILM).
19. A method as recited in claim 17 wherein one of said indicators of foveal location relates to the location of blood vessels in the image information.
20. A method as recited in claim 17 wherein the relative weighting of the indicators is adjusted based on the level of noise associated with the respective measurements.
21. A method as recited in claim 17 wherein the determined foveal location is indicated by indicia on a display of the image information.