Ocula fundus coordinate establishment

A polar coordinate system for retinal fundus image is set up based on the novel technique in the model-based, automatic localization of various landmark features of the retinal image. The technique begins with the detection of optic disk location by the Principal Component Analysis (PCA), the optic disk boundary detection by a point distribution model in combination with a modified active shape contour model (ASM), followed by main blood-vessel contour estimation, and finally the fovea localization. Thirty-five fundus images were tested successfully for fovea localization with three of them having results slightly deviated from those obtained by human observation. Once the fovea and the optic disk locations are known the coordinate system based on ETDRS recommendation can be established in a straightforward manner.