Types of Glaucoma ?
There are many different types of glaucoma. Most, however, can be classified as either open-angle glaucomas, which are conditions of long duration (chronic), or closed-angle (angle closure) glaucomas, which include conditions occurring suddenly (acute). 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 in that eye.
Open Angle Glaucoma
Chronic Open Angle Glaucoma (COAG)
Chronic open-angle glaucoma 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. 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
is a variant of open-angle glaucoma that is
being recognized more frequently than in the past. It 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. This results in increased pressure in the eye that can lead to the loss of vision from optic nerve damage and 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. Eye of the child enlarges and gives appearance of a larger eye like a Bull”s eye. Early diagnosis and treatment with medicine and/or surgery are critical in these infants and children to preserve their sight.
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 glaucoma vary, depending on the cause.
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 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 ( Pseudo Exfoliation )
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 most prevalent in older people and people of Scandinavian descent.
Closed Angle Glaucoma
Closed-angle glaucoma is a relatively common entity in Asia.. In this condition, the patient's intraocular pressure, which ordinarily is normal, can go up very suddenly (acutely). This sudden pressure increase occurs because the filtering angle becomes closed and blocks off 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 filtering angle to close. Thus, the problem in closed-angle 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.
People with small eyes are predisposed to developing closed-angle glaucoma because they tend to have narrow filtering 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 filtering angles, and an increased risk of developing closed-angle glaucoma. Furthermore, this condition may be triggered by medications that can dilate the pupils. These agents can be found in certain eye drops, cold remedies, or patches used to prevent seasickness. This condition can also occur spontaneously in a darkened room or a movie theater, wherein the pupil automatically dilates to let in more light. Sometimes, therefore, people with narrow angles are given eye drops to keep their pupils small.
A sudden glaucoma attack may be associated with
severe eye 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. 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.