Detecting an ellipse in a glaucoma photo?

For glaucoma diagnosis it is common to determine a "cup to disk ratio" which compares the diameter of the optic disk (VDD) and optic cup (VCD). The optical disk is visible as a circular red feature (red channel) and the optic cup shows up as a yellow circle (green channel). How can I calculate the diameter ratio between optic disk and optic cup?

I am able to detect the optic disk with canny edge detection, but I have not found a way to calculate the cup to disk ratio. How might I do that?

Answer 1

[Image Analyst]

There is no glaucoma toolbox so you're going to have to look to the literature for the algorithm. Start your search here http://www.visionbib.com/bibliography/contentsmedical.html#Medical%20Applications,%20CAT,%20MRI,%20Ultrasound,%20Heart%20Models,%20Brain%20Models and look up papers on retina image processing. You'll probably find something if someone has done it before. Then code it up.

[Indra Ginanjar A.T]

ya i have already doing it before.searh paper, journal and other. my program have already detect the optic disk with canny edge detection, but i have not found a way to calculate the diameter of optic disk and optic cup. from the paper was i read the way for calcute diameter optic disk and cup is using ellipse fitting. but I have not been able to find thats way.

[Image Analyst]

I can't help you write the algorithm from the paper. edge() does have a "Canny" option.