Glaucoma - Diagnosis

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If IOP is low or normal and tests report optic nerve damage and peripheral visual loss, doctors should also check for other conditions before starting any treatment for glaucoma. Such problems include steroid use, anemia, and previous hemorrhage or severe low blood pressure.

Ophthalmoscopy. The eye professional (or even a primary care doctor) uses an ophthalmoscope to peer through the pupil directly at the optic nerve. The examiner can then check the shape and color of the nerve fibers to evaluate whether they have been damaged by the high pressure of glaucoma. Damaged nerve fibers may be indicated by:

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• An asymmetrical or elongated cupped optic nerve
• The optic nerve color may be pale or an unhealthy-pink

If results show no optic nerve damage in patients who have mild elevations in pressure, the ophthalmologist may want to retest frequently but delay drug treatment, unless the patient has significant risk factors.

Fundus Photography. Fundus photography may be used to take pictures of the optic nerve and can reveal changes years in advance of vision loss. It is an unpleasant procedure requiring drops and a bright flash. This procedure has the same limitations as ophthalmoscopy.

Laser Polarimetry. Polarimetry uses laser technology to scan the eye and does not require any response from the patient. It is reported to be able to measure nerve fiber thickness in the eye and so be able to reveal early signs of deterioration. Preliminary studies have indicated that it has a diagnostic accuracy of over 90% for both confirming and ruling out glaucoma. One study, however, reported that laser polarimetry was sensitive enough to detect glaucoma in only up to 57% of patients with early glaucoma, 71% of those with moderate disease, and 81% of those with severe glaucoma. More research is needed.

Other Devices. Computer-assisted devices, such as the confocal scanning laser ophthalmoscope, are now available that may be useful for evaluating the retinal nerve layer. Another instrument, the optical coherence tomograph, measures the echo time delay of light that is scattered back from different layers in the retina. The value of these tests has not yet been determined.