Eye disease - Glaucoma (2 of 3)

Eye disease - Glaucoma (2 of 3):

What are glaucoma risk factors?

Glaucoma is often called "the sneak thief of sight." This is because, as already mentioned, in most cases, the intraocular pressure can build up and destroy sight without causing obvious symptoms. Thus, awareness and early detection of glaucoma are extremely important because this disease can be successfully treated when diagnosed early. While everyone is at risk for glaucoma, certain people are at a much higher risk and need to be checked more frequently by their eye doctor. The major risk factors for glaucoma include the following:

• Age over 45 years
• Family history of glaucoma
• Black racial ancestry
• Diabetes
• History of elevated intraocular pressure
• Nearsightedness (high degree ofmyopia), which is the inability to see distant objects clearly
• History of injury to the eye
• Use of cortisone (steroids), either in the eye or systemically (orally or injected)
• Farsightedness (hyperopia), which is seeing distant objects better than close ones (Farsighted people may have narrow drainage angles, which predispose them to acute [sudden] attacks of angle-closure glaucoma.)

What are the different types of glaucoma?

There are many different types of glaucoma. Most, however, can be classified as either open-angle glaucomas, which are usually conditions of long duration (chronic), or angle-closure (closed angle) glaucomas, which include conditions occurring both suddenly (acute) and over a long period of time (chronic). The glaucomas usually affect both eyes, but the disease can progress more rapidly in one eye than in the other. Involvement of just one eye occurs only when the glaucoma is brought on by factors such as a prior injury, inflammation, or the use of steroids only in that eye.

Open-angle glaucoma Primary chronic open-angle glaucoma (COAG) is by far the most common type of glaucoma. Moreover, its frequency increases greatly with age. This increase occurs because the drainage mechanism gradually may become clogged with aging, even though the drainage angle is open. As a consequence, the aqueous fluid does not drain from the eye properly. The pressure within the eye, therefore, builds up painlessly and without symptoms. Furthermore, as mentioned previously, since the resulting loss of vision starts on the side (peripherally), people are usually not aware of the problem until the loss encroaches on their central visual area.

Normal tension (pressure) glaucoma or low tension glaucoma are variants of primary chronic open-angle glaucomathat are being recognized more frequently than in the past. This type of glaucoma is thought to be due to decreased blood flow to the optic nerve. This condition is characterized by progressive optic-nerve damage and loss of peripheral vision (visual field) despite intraocular pressures in the normal range or even below normal. This type of glaucoma can be diagnosed by repeated examinations by the eye doctor to detect the nerve damage or the visual field loss.

Congenital (infantile) glaucoma is a relatively rare, inherited type of open-angle glaucoma. In this condition, the drainage area is not properly developed before birth. This results in increased pressure in the eye that can lead to the loss of vision from optic-nerve damage and also to an enlarged eye. The eye of a young child enlarges in response to increased intraocular pressure because it is more pliable than the eye of an adult. Early diagnosis and treatment with medicine and/or surgery are critical in these infants and children to preserve their sight.

Secondary open-angle glaucoma is another type of open-angle glaucoma. It can result from an eye (ocular) injury, even one that occurred many years ago. Other causes of secondary glaucoma are inflammation in the iris of the eye (iritis),diabetes, cataracts, or in steroid-susceptible individuals, the use of topical (drops) or systemic (oral or injected) steroids (cortisone). It can also be associated with a retinal detachment or retinal vein occlusion or blockage. (The retina is the layer that lines the inside of the back of the eye.) The treatments for the secondary open-angle glaucomas vary, depending on the cause.

Pigmentary glaucoma is a type of secondary glaucoma that is more common in younger men. In this condition, for reasons not yet understood, granules of pigment detach from the iris, which is the colored part of the eye. These granules then may block the trabecular meshwork, which, as noted above, is a key element in the drainage system of the eye. Finally, the blocked drainage system leads to elevated intraocular pressure, which results in damage to the optic nerve.

Exfoliative glaucoma (pseudoexfoliation) is another type of glaucoma that can occur with either open or closed angles. This type of glaucoma is characterized by deposits of flaky material on the front surface of the lens (anterior capsule) and in the angle of the eye. The accumulation of this material in the angle is believed to block the drainage system of the eye and raise the eye pressure. While this type of glaucoma can occur in any population, it is more prevalent in older people and people of Scandinavian descent. It is recently been shown to often be associated withhearing loss in older people.

Angle-closure glaucoma

Angle-closure glaucoma is a less common form of glaucoma in the Western world but is extremely common in Asia. Angle-closure glaucoma may be acute or chronic. The common element in both is that a portion of or the entire drainage angle becomes anatomically closed, so that the aqueous fluid within the eye cannot reach all or part of the trabecular meshwork. In acute angle-closure glaucoma, the patient's intraocular pressure, which ordinarily is normal, can go up very suddenly (acutely). This sudden pressure increase occurs because the drainage angle becomes closed and blocks off all the drainage channels. This type of glaucoma can occur when the pupil dilates (widens or enlarges). As a result, the peripheral edge of the iris can become bunched up against its corneal attachment, thereby causing the drainage angle to close. Thus, the problem in angle-closure glaucoma is the difficulty with access of the eye fluid to the drainage system (trabecular meshwork). In contrast, remember that the problem in open-angle glaucoma is clogging within the drainage system itself. In chronic open-angle glaucoma, portions of the drainage angle become closed over a long period of time. As more and more areas become closed, the pressure within the eye rises, often over a period of months or years.

People with small eyes are predisposed to developing angle-closure glaucoma because they tend to have narrow drainage angles. Small eyes are not obvious from their appearance, but they can be measured by an eye doctor. Thus, individuals who are farsighted or of Asian descent may have small eyes, narrow drainage angles, and an increased risk of developing angle-closure glaucoma. Furthermore, this condition may be acutely triggered by medications that can dilate the pupils. These agents can be found in certain eyedrops, cold remedies,citalopram (Celexa), topiramate(Topamax), or patches used to prevent seasickness. This condition can also occur spontaneously in a darkened room or a movie theater, when the pupil automatically dilates to let in more light. Sometimes, therefore, people with narrow angles are given eyedrops to keep their pupils small. (See the section below on parasympathomimetic agents.)

An attack of acute angle-closure glaucoma may be associated with severeeye pain and headache, a red (inflamed) eye, nausea, vomiting, and blurry vision. In addition, the high intraocular pressure leads to corneal swelling (edema), which causes the patient to see haloes around lights. Sometimes, acute glaucoma is treated with oral carbonic anhydrase inhibitors. (See the section below on these medications.) An attack of acute glaucoma, however, is usually relieved by eye surgery. In this operation, the doctor makes a small hole in the iris with a laser (laser iridotomy) to allow the fluid to resume draining into its normal outflow channels.

What are glaucoma symptoms and signs?

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Patients with open-angle glaucoma and chronic angle-closure glaucoma in general have no symptoms early in the course of the disease. Visual field loss (side vision loss) is not a symptom until late in the course of the disease. Rarely patients with fluctuating levels of intra-ocular pressure may have haziness of vision and see haloes around lights, especially in the morning.

On the other hand, the symptoms of acute angle-closure are often extremely dramatic with the rapid onset of severe eye pain, headache, nausea andvomiting, and visual blurring. Occasionally, the nausea and vomiting exceed the ocular symptoms to the extent that an ocular cause is not contemplated.

The eyes of patients with open-angle glaucoma or chronic angle-closure glaucoma may appear normal in the mirror or to family or friends. Some patients get slightly red eyes from the chronic use of eyedrops. The ophthalmologist, on examining the patient, may find elevated intraocular pressure, optic-nerve abnormalities, or visual field loss in addition to other less common signs.

The eyes of patients with acute angle-closure glaucoma will appear red, and the pupil of the eye may be large and nonreactive to light. The cornea may appear cloudy to the naked eye. The ophthalmologist will typically find decreased visual acuity, corneal swelling, highly elevated intraocular pressure, and a closed drainage angle.

Continued..,.