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Common Types of Glaucoma
The vast majority of patients with glaucoma in the western hemisphere have primary open angle glaucoma. This means that the eye otherwise looks normal except for the optic nerve damage. Other types of glaucoma have the same optic nerve damage, but the eye has other abnormal features. Examples of these "secondary" glaucomas include exfoliation glaucoma and pigment dispersion glaucoma. Other common types of glaucoma include angle closure glaucoma and neovascular glaucoma. The treatment for these last two conditions is different than for primary open angle glaucoma.Exfoliation glaucoma
Exfoliation glaucoma is a form of open angle glaucoma. It is distinguished from primary open angle glaucoma by the presence of abnormal deposits on the surface of the lens and other structures. Eye pressure can occasionally rise very rapidly in eyes with exfoliation glaucoma. It tends to occur in older patients and is more common in persons of Scandinavian descent. The treatment of both conditions is similar to primary open angle glaucoma.Pigment dispersion glaucoma
Pigment dispersion glaucoma is a form of open angle glaucoma. In pigment dispersion glaucoma, pigment is lost from the iris and is deposited on other structures, including the drainage channels. It is more common in younger patients, in males, and in near-sighted persons. It is treated with medications, laser, or surgery.Closed angle glaucoma
In angle closure glaucoma, the structures in the front of the eye are too crowded together to allow the normal flow of aqueous fluid both within the eye and out of the eye. In particular, the aqueous fluid has difficulty passing from behind the iris (colored part of the eye), through the pupil (hole in the center of the iris) to the anterior chamber (fluid filled area between the iris and the cornea (clear front part of the eye through which light passes). As a result, the iris is too close to the anterior chamber angle, where the fluid drains. This predisposes the eye to two potentially harmful situations. In acute angle closure glaucoma, there is a rapid elevation in eye pressure. The patient often notices eye pain, eye redness, and blurred vision. Because the very high eye pressure can rapidly damage the optic nerve, acute angle closure is a true emergency and requires immediate treatment by an ophthalmologist. In chronic angle closure glaucoma, the drainage tissues gradually become scarred, and the eye pressure rises slowly. This condition is generally silent, and severe glaucoma damage can occur without the patient's knowledge.Neovascular glaucoma
In neovascular glaucoma, abnormal blood vessels grow in the front part of the inside of the eye, blocking the drainage channels. This results in elevation of the eye pressure and damage to the optic nerve. The cause of the abnormal blood vessels is poor oxygen supply to the eye. The most common causes of neovascular glaucoma are diabetes, blockage of blood vessels in the back of the eye, and insufficient delivery of blood to the head due to blockage of the arteries in the neck.
Glaucoma is diagnosed by carefully studying the optic nerve and testing the field of vision. The optic nerve can be seen by the eye doctor with special equipment, after the pupils have been dilated. The hallmark optic nerve damage from glaucoma is abnormal "cupping". This refers to an abnormal depression in the center of the part of the optic nerve that is visible to the eye doctor. The presence of an abnormal amount of cupping leads the eye doctor to perform a visual field, or peripheral vision test, to help confirm the diagnosis. A peripheral vision test is an important part of the evaluation of glaucoma, because vision loss from glaucoma usually starts in the periphery. Based upon the results of the peripheral vision test and the appearance of the optic nerve, the doctor can state that you either have glaucoma, may have glaucoma, or do not have glaucoma.Visual field (peripheral vision) testing
Along with the doctor's examination of the optic nerve, visual field testing is the most important aspect of the evaluation for glaucoma. It represents the best way currently to determine how well you see. Although we often refer to peripheral vision testing, in fact, the test evaluates how well you see close to the center of your vision.
It must be emphasized that for all intents and purposes, glaucoma damage that has occurred can not be reversed. Therefore, the goal of treatment is the prevention of more glaucoma damage, not the reversal of pre-existing damage.
When to treat?
The decision to start treatment for glaucoma must be individualized for each patient. Treatment should be started when the benefits of treatment exceed the risks. In general, there are two situations in which treatment should be initiated.How much eye pressure lowering is enough?
One of the most difficult decisions in the treatment of glaucoma is determining how much the intraocular pressure should be lowered to avoid further damage to the optic nerve. The decision is difficult because optic nerves respond differently to the effect of high intraocular pressure. The physician will usually take into account the level of the intraocular pressure at which optic nerve damage occurred and the amount of damage already present in deciding on a "target" pressure for treatment.Laser, medicine, or surgery first?
For the past fifteen years glaucoma therapy has started with medications, proceeded to laser treatment only when medications were ineffective, and resorted to surgery only when the other methods had failed. The Glaucoma Laser Trial has demonstrated that laser treatment can be as effective as medication, leading the American Academy of Ophthalmology to state that laser treatment is an appropriate alternative to medication as the initial treatment for primary open angle glaucoma. A multicenter trial is in progress to evaluate the role of surgery (trabeculectomy) as the initial treatment for glaucoma, but the results will not be available for several years.Medicines
Medical treatment consists of either eyedrops or pills. Many types of glaucoma medications are available for use.How to take eyedrops
Administering eyedrops may take some practice. Perhaps the most important tip is to use the index finger of the hand that is not holding the bottle to pull down the lower lid. This forms a pocket into which the drop can be placed. If you are taking more than one type of eyedrop, 3-5 minutes should separate the application of the two drops. An important point to remember is that all eyedrops enter the blood stream and can potentially affect your whole body. The amount of eyedrop entering the blood stream can be decreased by closing your eyes after instilling the drop and by applying pressure on the skin between your eye and your nose.
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