General EYE ADVICE

Glaucoma

In routine examinations in this age group, the practitioner performs tests to detect any tendency to glaucoma. In this disease, the optic nerve fibres passing through the small round exit at the back of the eye, slowly degenerate at a point just before they exit the eye. This point at the back of the eye is called the optic disc. It can easily be seen on routine testing by the eyecare practitioner who assesses the disc's characteristics in detail. He may then monitor its appearance at regular intervals if the disc's appearance raises a suspicion of early glaucoma. This degeneration causes gradual loss of vision, often without the affected person's awareness. The degeneration of the nerve fibres occurs due to diminished blood flow at the optic disc, and possibly direct damage to the nerve axons from naked intra-ocular pressure. Degeneration of the tissue supporting the nerve axons due to high IOP, or other factors, can also lead to degeneration of the nerve axons.

This reduction in blood flow is most often caused by increased pressure within the eye. However, there are many other possible causes that are not well understood. These include vasospasm (abnormal muscle contraction leading to narrowing of the tiny blood vessels) and other vascular dysfunctions, cigarette smoking, lowered blood pressure (especially overnight and when caused by anti-hypertensive drugs), increased blood viscosity etc. (normal tension glaucoma). Future research will hopefully enlighten us further as to the causes and possible treatments for poor blood flow at the optic disc in the presence of normal pressure.

There are many causes of elevated eye pressure. Some people are clearly genetically disposed to develop high eye pressure. Another small proportion of people develop tissue changes within the eye from other internal eye pathology that can lead to impaired outflow of the fluid within the eye. However, many patients who develop high pressure within the eye, do not show any obvious causes. My own belief, as well as that of several authorities in the field, is that nervous stress plays an important role in many people who have raised eye pressures.

Other factors, that I have noted to play a role in raising eye pressure, are coffee (and possibly non-herbal tea intake), very intensive close work over long periods of time (without regular shifting of the focus), obesity, and body fluid retention (especially as a complication of certain medication). Unusually high volumes of fluid intake can also act to raise the eye pressure. High blood pressure appears to play a role in some individuals. Patients with undiagnosed, dangerously high blood pressure can present with significantly elevated eye pressure. Eye pressure can be controlled adequately in most people by medication, surgery or laser treatment.

In checking for glaucoma, the eyecare practitioner takes the pressure in the eyes and also looks into the fundus of the eye to check the health of the optic disc. A pale colour may signify the onset of glaucoma. Visual fields testing with automated equipment is performed to assess the state of the peripheral or side vision. This is usually the part of one's vision that is affected first in glaucoma. For further information on glaucoma you may link with the GLAUCOMA AUSTRALIA support group.

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