Optical Coherence Tomography
(OCT)Optical Coherence Tomography (OCT) is a non-invasive, non-contact imaging technique. It produces high resolution longitudinal cross-section tomographs of ocular structures.

OCT allows for earlier detection of glaucoma damage to the nerve fiber layer or optic nerve of the eye. It is the goal of these new glaucoma diagnostic tests to discriminate among patients with normal intraocular pressures who have glaucoma, patients with elevated intraocular pressure who have glaucoma, and patients with elevated intraocular pressure who do not have glaucoma.

A. Glaucoma along with cataract, diabetic retinopathy and macular degeneration is one of the four leading causes of blindness in adult Americans. Glaucoma usually can be controlled and vision loss prevented, however, almost 50% of patients with glaucoma remain undetected. Following and treating only those patients who have elevated intraocular pressure would miss glaucoma patients with normal intraocular pressure. Furthermore, it would result in unnecessary treatment for those patients with elevated intraocular pressure, but without glaucoma. The effective management of patients with pre-glaucoma and glaucoma involves careful evaluation of three modalities and follow-up.

1. The first is the intraocular pressure, which, although very useful to follow patients, is by itself not sufficient. There are patients who have ocular hypertension (high pressures without damage to the optic nerve) as well as patients with normal tension glaucoma (low pressures but extensive damage to the optic nerves).

2. The second is visual field testing which is highly beneficial for following progression of the disease. The problem with visual field testing is that until at least 50% of the over one million ganglion nerve fibers are damaged, there is no evidence of any field changes occurring. In patients with early glaucoma, it is very beneficial to make sure there are not any changes occurring as well as to make sure there are no other neurological or vascular abnormalities on the visual field test.

3. The third modality we need to follow is the appearance of the optic nerve. Stereo disc photos of the optic nerve have been useful but, with improvement in technology, we have proven sensitive indicators that can demonstrate optic nerve changes in a more sensitive manner in patients with glaucoma. In this regard, the scanning laser glaucoma test (SLGT) offers us a significant improvement in following patients for progressive damage to the optic nerve.