Changes in optic disc in ocular hypertension and glaucoma.

Most ophthalmologists use subjective methods to evaluate the optic disc for abnormalities and changes that occur in ocular hypertension and glaucoma. We have developed new techniques that allow more accurate evaluation of the blood supply to the optic disc and of changes in disc cupping and pallor. To evaluate the blood supply we use the technique of fluorescein angiography of the optic disc. With this technique, we have found that fluorescein defects commonly appear in open-angle glaucoma and ocular hypertension and are more frequent and larger in glaucomatous and ocular hypertensive discs than in normal optic discs. Fluorescein angiography demonstrates distinct changes in the blood supply to the optic disc in the glaucomatous or ocular hypertensive eye. Cupping of the optic disc is measured by photogrammetry from stereophotographs, which provide three-dimensional measurements not only of the volume of the cup, but of the depth, the slopes of the walls of the optic cup, and the area of the surface opening. This technique also allows us to determine a volume profile of the cup: that is, its cross-sectional area from top to bottom. The volume profile characterizes the shape of the optic cup and shows distinct differences in shape between normal, ocular hypertensive and glaucomatous cups. Pallor is measured by computerized image analysis. This technique allows us to determine the percent area of pallor of the optic disc. These three techniques permit us not only to evaluate abnormalities, but to measure changes over time in the optic disc in ocular hypertension and glaucoma, thereby increasing our diagnostic capability and improving patient management.