Abstract
Purpose :
Primary open-angle glaucoma (POAG) is defined as an optic neuropathy implying that nerve fibers (NF) are being atrophied similar to non-glaucomatous optic atrophies. Glaucomatous field defects reveal that NFs are being destroyed in an orderly sequence from peripheral-to-central. However, in non-glaucomatous optic atrophies, the NFs are being destroyed randomly. The purpose of this study was to determine if POAG is indeed an optic neuropathy.
Methods :
This comparative study included morphological analysis of optic disc fundus images. The compared groups included 25 glaucomatous discs (GD) and 25 non-glaucomatous atrophic discs (NGAD). Measuring parameters included: course of blood vessels, splinter hemorrhages on the disc margin, and notching at superior and inferior poles of the optic disc. The observation of these parameters were compared in both groups and deductive reasoning was applied.
Results :
The observed features in both groups were significantly different. The optic disc surface appeared sunken in the GD group, but were flat in the NGAD group. Also present in the GD group was sloping and kinking of blood vessels due to the sunken disc. Additionally, there was notching at the superior and inferior poles of the optic disc, and splinter hemorhages at the disc margin. These morphological features were not present in the NGAD group.
Conclusions :
Elevated IOP acting alone can't result in the orderly loss of NFs in glaucoma; only a mechanical process can achieve this outcome. It is proposed that elevated IOP may be destroying some important component of the optic disc first, thereby creating a mechanical process for the orderly loss of NFs in glaucoma.
Glaucoma may be a two-stage disease. The first (biological) stage involves elevated IOP compressing the circulation of the border tissue of Elschnig, resulting in chronic ischemia and its degeneration. The degenerated border tissue leads to loosening of the lamina cribrosa from the scleral wall. This is followed by the second (mechanical) stage: sinking of the lamina cribrosa resulting in the stretching and severance (axotomy) of NFs at the scleral edge in an orderly sequence from peripheral-to-central.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.