Basics of Glaucoma

Basics of Glaucoma

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History of eye trauma:

Injury to the eye may alter the structure of the eye, causing glaucoma.

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Use of steroids:

Some patients using steroids (“steroid responders”) may experience an

elevation in intraocular pressure.

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High myopia:

There is an association between open-angle glaucoma and myopia. High myopia

can also make optic nerve evaluation more difficult.

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High hyperopia:

Patients with high degrees of hyperopia usually have shorter eyes than normal.

As the patient ages, the anatomic structure of the eye changes, crowding the angles, which may

lead to increased intraocular pressure.

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Hypertension and cardiovascular disease:

Some patients with high blood pressure and

cardiovascular disease can experience the growth of abnormal new blood vessels. These vessels

may cover the trabecular meshwork, causing a buildup of aqueous humor.

CLASSIFICATION OF GLAUCOMA

The sections below describe the different classifications of glaucoma as outlined in the following table.

CLASSIFICATION OF GLAUCOMA

Primary/chronic open-angle glaucoma

Low tension glaucoma

Narrow-angle/angle-closure Glaucoma

Secondary glaucoma

(steroid responders, neovascular glaucoma)

Congenital glaucoma

Primary Open-Angle Glaucoma

Primary open-angle glaucoma is the most common form of the disease, affecting about 4 million

Americans. Approximately 90 percent of all glaucoma is considered open-angle glaucoma, although half

of these persons remain undiagnosed. Patients generally have no symptoms until considerable damage

has occurred. If left undetected, slow, progressive loss of field of vision will eventually occur.

During an eye examination, the anterior segment of the eye may look normal; however, subtle changes

may be occurring in the eye. The processes of the ciliary body produce aqueous fluid, which is important

to the physiology of the eye because the aqueous nourishes the cornea and the lens, removes waste

products, and maintains intraocular pressure. The aqueous fluid passes from the behind the iris, through

the pupil, into the anterior chamber. The fluid leaves the anterior chamber, passing into a portion of the

filtration angle, the trabecular meshwork, which has microscopic pores. The aqueous then flows into a

large drainage channel, Schlemm’s canal, which is circular and lies under the limbus. From Schlemm’s

canal, the fluid finally flows into the venous circulation of the eye by passing through the small episcleral

veins. Aqueous fluid also exits the eye through uveoscleral outflow, or diffusion through the rest of the

non-trabecular meshwork tissues.

In primary open-angle glaucoma, as in almost all other glaucoma, the pressure is elevated because the

aqueous does not drain out easily enough for the amount produced. Although the drainage area in open-

angle glaucoma appears to be open (unobstructed) on examination, there may be some blockage in the

tissues of the trabecular meshwork or below the surface.