Biostereometrics In Ophthalmology For Measurement Of The Optic Disc Cup In Glaucoma

Abstract

Glaucoma is a disease characterized by increased ocular pressure with optic nerve atrophy and loss of visual field or side vision which eventually leads to blindness. The surface of the portion of the optic nerve within the eye, the optic disc, becomes depressed and its contours are altered. The optic disc becomes more cupped with increasing progress of the disease. For measurement of the cup, retinal cameras can provide simultaneous stereo photographs of the optic disc taken through the pupil. However, the photographs have to be obtained at a narrow angle due to the limit of the size of the dilated pupil. Our studies of the geometry of the stereo photographs show a greater error in depth compared to horizontal dimensions because of this biological limit. Similarly, data for the optimal conditions for photography of the optic disc, including aperture size and magnification have been obtained. Since the changes in the optic disc can progress with increase of the desease, photogrammetric techniques for measuring relative changes in the dimensions of the cup have been developed. Both subsequent and initial photographs are measured after being similarly oriented in space. The photogrammetric measurement of changes in the optic disc cup in glaucoma has potential as a useful technique which can have wide clinical application.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.