Glaucoma is a condition in which the pressure inside the eye (the intra-ocular pressure –IOP) causes damage to the optic nerve, eventually leading to loss of vision. It is a “sneak thief” of vision, because the most common form of glaucoma does not cause any symptoms – no redness, no pain. Damage to the nerve occurs slowly and at first leads only to blind spots in the side vision, vision loss that is not noticed by the patient. Unless the pressure is lowered, vision loss will continue and worsen. Because vision lost to glaucoma cannot be recovered, early diagnosis and treatment is essential.
Glaucoma is a fairly common eye disease and is one of the leading causes of preventable blindness in the United States. Over 2 million Americans have been diagnosed with glaucoma and over 100,000 Americans are blind from this condition. Another million are at risk for vision loss because they don’t know they have it. In the U.S., glaucoma is the leading cause of blindness among African-Americans and Hispanics.
The best way to prevent loss of vision from glaucoma is to have regular examinations by an ophthalmologist. At Ophthalmology Associates we are skilled at the detection of glaucoma and routinely check for its earliest signs. When glaucoma is diagnosed and treated early, loss of vision and blindness can usually be prevented.
WHAT CAUSES GLAUCOMA?
Clear liquid, called aqueous, circulates inside the eye, constantly being made and constantly being drained. (This is not the tears which are outside the eye and have nothing to do with the pressure) The balance between the production and drainage of aqueous results in an internal pressure in the eye. If the drainage pathways out of the eye (the trabecular meshwork in the angle) become clogged or less efficient, the pressure inside the eye will increase and may cause damage to the optic nerve (the nerve that carries visual information to the brain). The pressure at which damage occurs is variable – that is, there is no specific number that means a person has glaucoma. However, in general, the higher the pressure, the more likely it is that glaucoma will develop.
TYPES OF GLAUCOMA
Primary Open Angle Glaucoma (POAG): This is the most common form of glaucoma in the United States and most often affects those over 40. The rise in pressure and subsequent optic nerve damage is very gradual and no symptoms are noticed until damage has become severe. Early diagnosis is only possible through careful and repeat examinations.
Narrow Angle Glaucoma (NAG): In some people the anatomy of the eye is such that the drainage angle can suddenly become completely blocked and the pressure inside the eye can rise very high very quickly. When this occurs it is called acute angle-closure glaucoma. An attack of angle closure glaucoma causes symptoms including severe eye pain, headache, red eye, blurred vision and nausea and vomiting. This is an emergency and requires prompt treatment or blindness can result. Angle closure glaucoma is more common in Asian people than in those of European descent and is rare in African-Americans.
HOW IS GLAUCOMA DIAGNOSED?
Having regular eye examinations by your ophthalmologist is the best way to find early glaucoma. The diagnosis is sometimes obvious and at other times quite difficult. Various tests are done during the examination and these are evaluated in light of other risk factors. Often the suspicion of early glaucoma will be raised and follow-up over time will determine if treatment is needed.
Tests that might be done to help determine if glaucoma is present include:
Tonometry – the measurement of intraocular pressure
Pachymetry – measurement of the central thickness of the cornea
Gonioscopy – inspection of the drainage angle of the eye
Ophthalmoscopy – looking at the nerve at the back of the eye
Perimetry – testing of the side vision (visual field)
Retinal Tomography – a computerized scanning laser picture and analysis of the
optic nerve to look for damage from glaucoma and provide a means for evaluating possible change over time
Risk factors for glaucoma include:
• Increasing age
• Family history of glaucoma
• Elevated intraocular pressure
• History of trauma to the eyes