By Jacob T. Wilensky, MD, Professor
Glaucoma is one of the major causes of blindness in America. It is not a single disease but rather a group of conditions that have different causes, manifestations, and treatments. What ties these conditions together is an increased pressure inside the eye (elevated intraocular pressure) that causes the death of retinal nerve cells and thereby produces blindness. It occurs predominantly in the elderly, but can occur at any age from birth onward.
A fluid called aqueous humor is constantly circulating in the front part of the eye. It brings nutrition to the lens and to part of the cornea, as these structures have no blood vessels to perform that function. The ciliary body constantly produces new fluid that flows through the pupil into the anterior chamber. This fluid then leaves the eye through a drain called the trabecular meshwork. In glaucoma something interferes with this flow such that the aqueous does not leave the eye as rapidly as it is produced, increasing the pressure inside the eye. This high pressure in time leads to the death of retinal nerve cells (those cells that actually “see”), thus leading to blindness.
Two main types of glaucoma occur, depending on the individual eye. In some eyes the anatomic structures are close and crowded together. Because of this configuration, under certain circumstances, the iris can come forward and touch the back of the cornea. When this happens, access to the Trabecular meshwork is blocked, the aqueous cannot leave the eye, and the intraocular pressure rises rapidly. This type of glaucoma is called angle closure glaucoma. The eye may become red and may tear a lot. The cornea may become “steamy” producing blurred vision and rainbows or halos around lights. A person may experience pain in or around the eye and occasionally nausea and vomiting. This acute form of glaucoma can cause rapid loss of vision leading to total blindness in merely a day or two if appropriate treatment is not promptly instituted.
The immediate treatment of angle closure glaucoma consists of eye drops that make the pupil small (Miotics) and liquids taken orally or intravenously that shrink the volume of the eye and thereby decrease the intraocular pressure. This therapy is only temporary. The permanent treatment of angle closure glaucoma requires making a hole through the iris (Iridectomy). This usually is accomplished with laser energy that is focused into a special, very powerful light beam. Occasionally, however, it is necessary to perform a surgical procedure, in which a piece of the iris is removed with scissors.
The other major type of glaucoma is open angle glaucoma. It is the predominant type of glaucoma in the United States. It has a higher prevalence in African-Americans and Hispanics. This condition progresses very slowly and is often symptom-free until very late in its course. The intraocular pressure rises gradually over a period of months to years and slowly causes loss of vision. Usually the side (peripheral) vision is lost first, and only late in the disease is the central or reading vision affected. Because of this lack of symptoms many patients with open angle glaucoma are unaware that they have the disease and that they are losing sight. Regular ophthalmic examinations that include measurement of the intraocular pressure (Tonometry) an examination of the optic nerve head with an ophthalmoscope will permit detection of the disease, even in the symptom-free patient.
The treatment of open angle glaucoma primarily entails the use of eye drops to decrease the pressure inside the eye. These drops must be used daily and usually more than once a day. Some patients require several different kinds of eye drops to control the glaucoma. In a large majority of patients these drops successfully control the glaucoma and prevent blindness. In the remaining patients, laser treatments or surgical procedures that create an artificial drain for the eye can be used to control the glaucoma in most instances.
Commonly asked questions about Glaucoma
There is definitely an increased familial incidence of the two types of glaucoma that have been discussed. Someone who has a parent, brother, or sister with one of these types of glaucoma will have about a one in ten chance of developing the condition. There are other secondary types of glaucoma that may or may not be hereditary.
Are eye pressure and blood pressure the same thing?
No. Some people have high blood pressure but normal eye pressure, and vice versa. However, some (but not all) of the drugs that are used to treat high blood pressure also lower the intraocular pressure.
Should glaucoma patients stop drinking coffee?
Glaucoma patients who drink a lot of any clear fluid, whether water or black coffee, can experience a temporary increase in their intraocular pressure. Therefore, glaucoma patients should not drink a lot of fluids at one time. Our study of glaucoma patients who drink two cups of regular coffee a day showed that coffee has no greater effect on glaucoma than other beverages.