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Optic Nerve Cupping
Q&A
What is optic nerve cupping?
The optic nerve carries impulses for sight from the retina in the eye to the brain. It is composed of millions of retinal nerve fibers that bundle together and exit to the brain through the optic disc located at the back of the eye. The optic disc has a center portion called the “cup” which is normally quite small in comparison to the entire optic disc.
In people with glaucoma damage, because of increased pressure in the eye and/or loss of blood flow to the optic nerve, these nerve fibers begin to die. This causes the cup to become larger in comparison to the optic disc, since the support structure is not there. Optic nerve cupping progresses as the cup becomes larger in comparison to the optic disc.
Both people with and without optic nerve damage have optic nerve cupping, although those with glaucoma tend to have a greater cup-to-disc ratio. A cup to disc ratio greater than six-tenths is generally considered to be suspicious for glaucoma. Through periodic photographs of the optic nerve, the ratio of the cup to the disc can be monitored. This helps the doctor determine whether or not damage is still occurring to the nerve fibers with current treatment and/or if treatment should be modified.
I’ve been told that I’ve lost 80 percent of my optic nerve. However, my doctor says I have good to fair vision. I thought that optic nerve damage is what causes you to lose your sight-how can I have so much optic nerve damage and still have good to fair vision?
Certainly an optic nerve that has been visually observed by the eye doctor to be 80 percent damaged is more fragile than an optic nerve with less damage. However, an estimate of glaucoma damage looks at more than optic nerve damage. Usually, an eye doctor will estimate the extent of damage to vision by evaluating the amount of damage to both the visual field and the optic nerve. This is determined by eye examinations.
Q & A by Scott Burk, MD, PhD, Associate Ophthalmologist, and John S. Cohen, MD, Chief of Glaucoma Services, Cincinnati Eye Institute, Cincinnati, OH, and Harry Quigley, MD, Director of the Glaucoma Service, Wilmer Ophthalmology Institute, Johns Hopkins Hospital, Baltimore, MD.
reviewed 9-4-08
This article appeared in the Winter 1999 issue of Gleams. Subscribe