Glaucoma is a group of eye conditions that cause optic nerve damage in the eye, leading to vision loss and blindness. Unusually high pressure inside the eye, or intraocular pressure, causes glaucoma, according to the National Eye Institute.
Glaucoma is the second-highest cause of blindness and damages sight gradually in most cases. According to the Mayo Clinic, the most common type, primary open-angle glaucoma, does not have noticeable symptoms except gradual vision loss. There are several causes for glaucoma, though it cannot always be determined why symptoms occur.
Obstructed Eye Drainage
The University of Maryland Medical Center says the main cause of increased pressure in the eye is that aqueous humor builds up in it. Aqueous humor is a fluid that is naturally produced in the front of the eye and is normally constantly drained from the eye. In primary open-angle glaucoma, some of the microscopic drainage channels called the trabecular meshwork become partially obstructed. The exact cause of this is not known.
Bulging Iris
In angle-closure glaucoma, the drainage channels of the eye remain open, but the iris of the eye bulges forward to block the drainage angle between the cornea and the iris. Aqueous fluid from the eye can then not drain, and the eye pressure builds up, damaging the optic nerve. The cause of iris bulging is not known, but it may have genetic reasons.
Optic Nerve Damage
The University of Maryland Medical Center notes that low-tension glaucoma is a form of glaucoma that is not well understood, though it occurs often. In this type of eye disease, the pressure in the eye stays normal, but the optic nerve becomes damaged for unknown reasons. This may occur due to unusually sensitive optic nerve or atherosclerosis, or hardening of the blood vessels to the eye, reducing oxygen and nutrient flow to the optic nerve.
Pigment Granule Dispersal
Pigmentary glaucoma is linked to pigment granules in the eye and is most easily diagnosed by an ophthalmologist. It occurs when pigment granules accumulate on and in the drainage channels, the trabecular meshwork, interfering with the outflow of fluid and raising the pressure in the eye. Pigment granules can be dispersed by injury or even physical activity, causing them to move to the wrong places in the eye.
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