Digital stereo optic disc image analyzer for monitoring progression of glaucoma

This paper describes an automated 3-D surface recovery algorithm for consistent and quantitative evaluation of the deformation in the ONH (optic nerve head). Additional measures, such as the changes in the volume of the cup and the disc as an improvement to the traditional cup to disc ratios, can thus be developed for longitudinal follow-up study of a patient. An automated computerized technique for stereo pair registration and surface visualization of the ONH is proposed. Power cepstrum and zero mean cross correlation are embedded in the registration and a 3-D surface recovery technique is developed. Preprocessing, as well as an overall registration, is performed upon stereo pairs. Then a coarse to fine feature matching strategy is used to reduce the ambiguity in finding the conjugate pair of the same point within the constraints of the epipolar plane. A cubic B-spline interpolation smoothes the representation of the ONH obtained, while superimposition of features such as blood vessels is added. Studies show high correlation between traditional cup-to-disc measures derived from manual segmentation by ophthalmologists and computer generated cup-to-disc volume ratio. Such longitudinal studies over a large population of glaucoma patients are currently in progress for validation of the surface recovery algorithm.