The Use of the OCT Test in Glaucoma
OCT - Ophthalmic Computerized Tomography
Retinal Nerve Fiber Layer (RNFL) and Ganglion Cell Complex (GCC)
In the last blog, I talked about how important it is for us to evaluate the optic nerve in monitoring glaucoma suspects and glaucoma patients. Any changes in the cupping or the healthy rim of the nerve could denote a worsening of its health. The optic nerve is like a large telephone cable that leads from the retina back to the brain. This cable is fed by about one million individual wires or neurons that come from all parts of the retina. We've learned that before the optic nerve becomes damaged, these individual wires start to become damaged and change in thickness. If they are under stress or damaged, they become thinner. If enough of those individual wires become thinner, we actually will see a corresponding loss of health of the optic nerve in that area.
To minimize the risk of glaucoma, we need to look at the retinal nerve fiber layer and assess its health. We use an OCT test in our office -- which is a scan of the optic nerve -- to assess the health over time. Because this test has been performed thousands of times, we know what the average thickness of the nerve fiber is for any given patient. If we start to see thinning in an area, we watch this very closely or assess other methods of lowering your eye pressure to keep your optic nerve healthy.
Posted on 01/21/2015 8:40 AM by Dr. Susan Kegarise
Glaucoma: The Optic Nerve and Fundus Exams
January is Glaucoma Awareness Month and we have some special updates this month about this optic nerve disease. Over the years we have developed more sophisticated ways to look at the health of the optic nerve.
In the past, most eye doctors used a handheld instrument and came in close to you, shining this light in your pupil. This was a "one-eyed" view. The more modern and effective way for us to look at the optic nerve now is with a high powered magnification lens at the microscope. This gives us more depth perception due to the binocularity of the microscope.
We're looking for the overall nerve shape and the "inner cup". In most people, the optic nerve looks like a donut. The cup would be the hole in the middle of the doughnut. Cupping varies from patient to patient and is about 1/3 of the diameter of the optic nerve. This ratio is important and is recorded on your chart at every visit. During follow-up visits we measure the cupping. If we see the cupping increasing we know you are potentially losing healthy optic nerve tissue. This is certainly a high risk factor for glaucoma and necessitates additional testing. What's important to remember is that if we keep your optic nerve healthy you will not lose vision due to glaucoma.
Posted on 01/06/2015 7:38 AM by Dr. Susan Kegarise