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What is glaucoma?
Glaucoma is a specific pattern of optic nerve damage and visual field loss caused by a number of different eye diseases which can affect the eye. Most, but not all of these diseases, are characterized by elevated intraocular pressure, which is not the disease itself, but the most important risk factor for the development of glaucoma.
The disease is called the sneak thief of sight because it strikes without obvious symptoms. Therefore, the person with glaucoma is usually unaware of it until serious loss of vision has occurred. In fact, half of those suffering damage from glaucoma do not know it. Currently, damage from glaucoma cannot be reversed.
Who is at risk for glaucoma?
Everyone should be concerned about glaucoma and its effects. It is important for each of us, from infants to senior citizens, to have our eyes checked regularly, because early detection and treatment of glaucoma are the only ways to prevent vision impairment and blindness. There are a few conditions related to this disease which tend to put some people at greater risk. This may apply to you if:
- you are over 45 and have not had your eyes examined regularly
- someone in your family has a history of glaucoma
- you have abnormally high intraocular pressure
- you are of African descent
- you have diabetes
- myopia (nearsighted)
- regular, long-term steroid/cortisone use
- previous eye injury
In angle-closure glaucoma, intraocular pressure (IOP) can increase suddenly, causing an angle-closure (acute glaucoma) attack. This attack can occur within a matter of hours and become very painful. Possible indications include:
- intense pain, which may result in nausea and vomiting
- red eye(s)
- swollen or cloudy cornea(s)
- halos around lights (rainbow-colored rings around lights)
- recurrent blurry vision
- morning headaches
- pain around your eyes after watching TV or leaving a dark theater
Detection and Diagnosis
Because glaucoma does not cause symptoms, in most cases those who are 40 or older should have an annual examination including a measurement of the intraocular pressure. Those who are glaucoma suspects may need additional testing.
The glaucoma evaluation has several components. In addition to measuring the intraocular pressure, the doctor will also evaluate the health of the optic nerve (ophthalmoscopy), test the peripheral vision (visual field test), and examine the structures in the front of the eye with a special lens (gonioscopy) before making a diagnosis.
The doctor evaluates the optic nerve and grades its health by noting the cup to disc ratio. This is simply a comparison of the cup (the depressed area in the center of the nerve) to the entire diameter of the optic nerve. As glaucoma progresses, the area of cupping, or depression, increases. Therefore, a patient with a higher ratio has more damage.
The progression of glaucoma is monitored with a visual field test. This test maps the peripheral vision, allowing the doctor to determine the extent of vision loss from glaucoma and a measure of the effectiveness of the treatment. The visual field test is periodically repeated to verify that the intraocular pressure is being adequately controlled.
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