Optic disc histomorphometry in normal eyes and eyes with secondary angle-closure glaucoma. I. Intrapapillary region.

The intrapapillary region of the optic disc shows ophthalmoscopical changes in glaucoma. In search of a histological correlate, this region was examined histomorphometrically in serial sections of 21 human eyes with secondary angle-closure glaucoma and 28 control eyes with malignant choroidal melanoma. The lamina cribosa was significantly (P less than 0.05) thinner, the optic cup deeper and wider, the peripapillary scleral ring finer, and the corpora amylacea count was lower in glaucoma eyes than in control eyes with normal optic nerves. There was no significant difference in optic disc diameter. The decrease in lamina cribrosa thickness may be one of several factors leading to glaucomatous optic nerve fiber loss. Due to a decrease in the relative height the inner limiting membrane should not be taken as the reference level for optic-cup-depth measurement. A high corpora amylacea count may point to a normal optic nerve fiber population.