Glaucoma : Causes and Risk Factors

Causes of open-angle glaucoma include:

  • Aging - The aging process reduces the size of the eye's drainage angle, resulting in increased intraocular pressure.
  • Genes - Several genetic factors can contribute to glaucoma. Mutations in the GLC1A gene cause it to overproduce a substance that clogs the angle where fluid drains from the eye. In addition, the LMX1B gene is believed to cause some cases of glaucoma.
  • Nitric oxide deficiencies - Low levels of nitric oxide contribute to unhealthy blood vessels, which in turn elevate intraocular pressure.
  • Nutritional deficiencies - This may cause damage to optic nerve fibers.
  • Brain chemical abnormalities - Large amounts of glutamate (a neurotransmitter) can contribute to the destruction of nerve fibers within the eye.
  • High Intraocular (Eye) Pressure
  • Positive family history of glaucoma in a first degree relative
  • Suspicious optic nerve appearance (cupping > 50% or assymetry)
  • Central corneal thickness less than 555 microns (0.5 mm)
  • High Myopia (near sightedness)
  • Diabetes
  • Hypertension
  • Eye Injury or Surgery
  • History of steroid use
  • Migraine headache and peripheral vasospasm
  • Sleep-related breathing disorder

Closed-angle glaucoma, a rare form of the disease accounting for just 15 percent of all glaucoma cases in the country, is caused by a structural defect within the eye that creates a narrow angle between the iris and cornea. If the iris slips forward, it may block the fluid drainage angle. This condition can be triggered by medications that dilate the pupil, such as antihistamines and tricyclic antidepressants. It can also occur naturally, when the eye dilates in low light. People who suffer from hyperopia (farsightedness) are at a heightened risk for acute closed-angle glaucoma because their eyes have narrow drainage angles. Closed-angle glaucoma produces symptoms of severe eye pain, blurred or haloed vision, nausea, vomiting, and headache.

Everyone over age 60 has an increased risk for glaucoma. Other groups at increased risk include Blacks over age 40.
Glaucoma is also three to four times more likely to occur in Blacks than in Whites. In addition, glaucoma is six times more likely to cause blindness in Blacks than in Whites. Blacks have thinner corneas than whites (by about 23 microns) and this may well be the factor that puts blacks at a higher risk for glaucoma progression (per EMGT study data).

Although it is clear that genetics plays an important role in primary open angle glaucoma, details about the inheritance remain unclear. No single mode of inheritance can adequately describe glaucoma as a whole. It seems that glaucoma development depends not so much on a single gene but rather upon the interaction of several genes and possibly environmental factors too.

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