PHOTOGRAMMETRY OF THE OPTIC DISK IN GLAUCOMA AND OCULAR HYPERTENSION WITH SIMULTANEOUS STEREO PHOTOGRAPHY

Abstract

Stereophotogrammetric evaluations of the optic cup were performed for normal, ocular hypertensive and glaucomatous [human] eyes. Average volume, area and depth measurements were progressively larger from normal to ocular hypertensive to glaucomatous eyes, although the distributions of individual values exhibited considerable overlap among the 3 groups. Similar results were obtained for volume, area and depth asymmetry between each pair of eyes. None of these measurements distinguished accurately between normal and glaucomatous optic cups. Normal eyes showed a high correlation (r = +0.85) between area and depth of the optic cup. This area/depth relationship was reduced in ocular hypertensives (r = +0.63) and completely broke down for glaucomatous eyes (r = +0.04). Approximately 89% of the glaucomatous eyes and 47% of the ocular hypertensive eyes were beyond the range of normal area/depth correlation values. Previous attempts to quantitatively differentiate between normal and glaucomatous eyes on the basis of optic disc measurements were less accurate and implied optic disc damage usually precedes visual field loss in glaucoma. With further technical refinements such as computer image processing, stereophotogrammetry of the optic cup may become a valuable differential diagnostic technique for glaucoma.