Comparison of optic disc features in low-tension and typical open-angle glaucoma

This study was undertaken to identify features of optic nerve head architecture that might explain, in part, why ganglion cell loss occurs in patients with low-tension glaucoma. We compared retrospectively the disc photographs of 25 patients with low-tension glaucoma with those of 26 control patients with typical open-angle glaucoma. No differences were observed in any of the following features: pore length, shape, or size variation; cup/disc and disc/arteriole ratio; clock positions of total rim loss; central retinal vessel entry site; rim pallor; number of rim-crossing vessels; and presence or absence of peripapillary nerve fiber layer hemorrhages, optic pits, and central retinal vessel canals. An hour-glass appearance of connective tissue bundles within the scleral lamina cribrosa, however, was present statistically less often in patients with low-tension glaucoma (p = 0.007). We speculate that the microscopic arrangement of fiber bundles within the lamina cribrosa may play an etiologic role in the pathogenesis of low-tension glaucoma.