It is widely mentioned that physiological cup starts enlarging in glaucoma due to raised IOP. What are the physiological cups? According to Wolf’s Anatomy the physiological cups are produced due to varying degree of atrophy of the Bergmeister’s papilla - a tuft of hyaloid vessels providing nutrition to the lens in the fetal life. In histology of normal disc (Wolf’s anatomy & other sources) this remnant fibrous tissue is identified as central connective tissue meniscus (CCTM) lying superficially on the surface of the nerve fibers layer. Some discs have none of CCTM meaning having no cup and some discs may have CCTM as large as covering 90% of the surface or having 0.9 physiological cup.
It is also mentioned that the nerve fibers are present only in the rim area (exposed area) whereas the central cupped area is empty and devoid of nerve fibers. It appears a fallacy, as there is no such histology supporting this doughnut shaped arrangement in any normal or diseased disc.
Returning to our main question: if the physiological cups are remnant fibrous structure then few puzzling questions arise: First, why should a fibrous structure enlarge in response to high or normal IOP to begin with ? Second, why should a fibrous plate enlarge concentrically in diameter due to raised IOP, defying the laws of physics, and not instead deepen and thus reducing its diameter? I have not seen any physiological cup enlarging concentrically say from 0.3 all the way to 100% cupped in glaucoma and there is no documentation of such a gradual concentric enlargement either. It is mentioned the occurrence of notching in the superior and inferior pole of the physiological cup in the early stages of glaucoma which is breaking of the physiological cup and certainly not its concentric enlargement.
Third, the histology of end-stage glaucomatous disc (ESGD) reveals an empty crater: it appears neither 100% cupped physiological cup nor 100 % cupped lamina cribrosa.
ESGD appears to be a crater in an area which once the housed the disc. It is totally devoid of nerve fibers, physiological cup, lamina cribrosa and even the vasculature except few large vessels hanging on its rim. Where did all these structures go? What structure of the disc has really become 100 % cupped or is it a fallacy?
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