Types
While more than 40 types of glaucoma can occur, the following are the most common forms of open angle and angle closure glaucoma:
Open Angle Glaucomas
The most common form of glaucoma, called open angle glaucoma, is a so-called “silent disease” in its early stages. It is painless, and the vision loss that occurs is typically not noticeable until after significant damage has already been done. For this reason, everyone should have regular eye exams, and people with a family history or personal risk factors for glaucoma should undergo even more frequent screenings for the disease.
Primary Open Angle Glaucoma
Primary is the most common form of open angle glaucoma. It is called “primary” because it occurs in absence of other eye conditions which could cause glaucoma.
Pseudoexfoliation Glaucoma
A form of open angle glaucoma in which dandruff-like material collects inside the eye, and can cause dysfunction of the trabecular drain.
Pigmentary Glaucoma
A form of open angle glaucoma in which pigment from the iris becomes abnormally mobile in the eye and may cause dysfunction in the trabecular drain.
Angle Closure Glaucomas
Though far less common than open angle glaucoma, angle closure glaucoma can also cause damage to the optic nerve, though sometimes much more rapidly and in a painful fashion that is noticeable to the patient. These glaucomas are diagnosed by the presence of iris tissue, abnormal blood vessels or scar tissues physically closing off the trabecular drainage system. With the trabecular drain closed, the eye pressure can increase greatly which, if allowed to persist, results in the characteristic optic nerve and/or visual field loss typical of glaucoma.
Primary Angle Closure Glaucoma
Occurs due to an anatomical abnormality of the eye in which the iris may periodically come in contact with the lens of the eye. This may occur when the iris is partially dilated, which happens in lower light situations like a movie theater. The lens-iris contact, called pupillary block, may result in abnormal flow of aqueous fluid within the eye, and cause the iris to compress against the cornea over the trabecular drain, closing off the outflow path for the aqueous fluid. As a result, the eye pressure can increase dramatically, often in a rapid fashion, resulting in pain and acutely decreased vision.
Neovascular Glaucoma
Several forms of eye disease, such as diabetes and vascular problems of the eye, can result in the growth of new blood vessels over the trabecular meshwork. With the new blood vessels also comes scar tissue, which can close off the trabecular drain directly or by pulling iris over it as the scarring progresses. As a result, the eye pressure can increase greatly and glaucomatous damage to the optic nerve can occur.
Angle Recession Glaucoma
When an eye suffers from a blunt injury, such as being hit with a softball, the trabecular drainage system of the eye can become damaged. If enough of the drain is damaged, malfunction of the drainage of aqueous eye fluid can occur, leading to a rise in eye pressure and subsequent glaucomatous damage to the optic nerve. The rise in eye pressure with angle recession glaucoma often occurs many years after the eye was injured.
