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Updated: May 10, 2025
The development of the pale circle which surrounds the disc, particularly in glaucomatous eyes, is due to a very slight recession of the pigment layer of the retina and of the margin of the chorioid at this point with some atrophy, apparently consequent on the beginning retraction of the lamina cribrosa and slightly increased pressure of the nerve fiber layer on the underlying tissues at the margin of the disc.
Tiny clear spaces form in the lamina cribrosa and in front and behind it in the nerve tissue. Their exact nature is unknown. Usually they are entirely empty, often they are traversed by fine glial fibers. They seem to be in no relation to the blood vessels. Adjoining lacunae are supposed to fuse to form larger cavernae and these finally merge and constitute the final glaucoma cup.
The excavation of the disc progresses slowly and is due in part to stretching the fibers of the lamina cribrosa pressing this structure outward, and partly to atrophy and disappearance of the nerve tissue and much of the vascular tissues in the nerve head. The displacement backward of the lamina cribrosa may cause that structure to lie behind the outer surface of the sclera.
However, the change in the position of the lamina cribrosa must exert a deleterious effect, particularly on those fibers which pass through the peripheral meshes, the shape of which must necessarily be much distorted. XLII. p. 145; Opin. Soc. Arteries and veins are both affected. Hyaline degeneration of the media also occurs. The process is not uniform. Glaucomatous Cup.
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