[Contributory factors for glaucomatous disc cupping. 4. Generalized expansion type and localized type]

It is widely recognized that there are two types progressive disc cupping in glaucoma. One of them is the localized type (L type) in which the cupping extends to a certain direction and the other is the generalized expansion type (G type) in which the cupping expands generally. We evaluated the optic disc in 86 eyes with primary open angle glaucoma (G type 44 eyes L type 42 eyes) to evaluate correlations of age and visual field defects between the 2 groups. Our study revealed that G type patients were significantly younger than those with L type when matched according to visual field defects. We also found that G type was revealed as the nasal step alone but not in L type. These results suggest that in G type, the optic nerve head is diffusely damaged by elevated intraocular pressure and the total nerve fibers are destroyed uniformly. On the other hand, in L type, the vulnerable portion of the optic nerve head is selectively damaged and nerve fibers constituting the optic rim area are destroyed. As a result, L type is likely to form cupping notch and reveal Bjerrum scotoma. These facts correspond to the anatomical structures of nerve fiber layers.