I agree with Dr. Lewis' disappointment that we have not accomplished more in the field of glaucoma and that we have gained little understanding of glaucomatous cupping in the absence of elevated IOP. I may add that we have accomplished little in past 150 years, when the disease entity of simple chronic glaucoma along with the term cupping were introduced. Perhaps glaucomatous cupping may not be occurring at all. Everyone has his own opinion about the failure of understanding of glaucoma, but I attribute it to the term cupping, which was mistakenly attached with simple glaucoma. Over the past 150 years, the term cupping has become synonymous with primary open-angle glaucoma. No questions were asked.
As I understand the term, glaucomatous cupping implies when the physiological cup begins enlarging concentrically. In other words, the pathology initiates from the center and extends to the peripheral part of the optic disc. Cupping has failed to explain early arcuate field defects, nasal shifting of the blood vessels, and its occurrence in normal-tension glaucoma. I believe that glaucomatous cupping may not be occurring and that normal-tension glaucoma may be a systemic disease and nothing to do with IOP.
Histology of the end-stage glaucomatous disc reveals … an empty crater. There is no optic disc and no nerve fibers. What has happened to the optic disc? Where did it go? Did the optic disc melt as a result of raised IOP or due to apoptosis of the ganglion cells of the retina? Not in my opinion. I believe some mechanism has severed the retinal nerve fibers before they entered the optic disc. I hypothesize that the optic disc may be sinking in its entirety, causing the deeper peripheral fibers to be severed first by the scleral edge and ending with the central fibers.1,2 This is what I believe optical coherence tomography is revealing—that there is thinning of the retinal nerve fiber layer. Ironically, if the cupping were occurring, then the fibers for the central vision, which lie in the central part of the disc and are also located superficially (closer to the vitreous), would have been destroyed first, but this is not the case. The glaucomatous disc becomes unique compared with other kinds of atrophic discs where the nerve fibers, though shrunken, are still present. In the end-stage glaucomatous disc, however, there is total amputation of the optic disc. Why do we call it a 100% cupped disc when the disc is no longer present?
Syed S. Hasnain, MD
Porterville, California
