Pathogenesis of cupping of the optic disc.

Optic disc cupping (ODC) is a classical feature of chronic simple glaucoma. In attempts to explain the pathogenesis of ODC, a very large volume of literature has accumulated since its discovery over I 20 years ago, but the mechanism is still far from clear. The presence of ODC with no rise in intraocular pressure (IOP), first described by von Graefe (I857), has further contributed to the confusion on the subject. Various theories attempt to explain the pathogenesis of the changes in the optic disc (OD) in these cases, postulating either a mechanical or a vascular basis, in addition to many more theories concerning cavernous degeneration; the subject has been reviewed elsewhere (Hayreh, I974d).