~ Glaucoma ~
What is Glaucoma?
Open-angle glaucoma is a pattern of vision loss with increased pressure inside the eye. This eye pressure is known as intraocular pressure (IOP). Glaucoma, which may cause blindness, usually has no warning signs. Not knowing you have glaucoma is a person's greatest risk. This is only a resource of signs and symtoms. Simple tests performed by your eye doctor can diagnose glaucoma.
Glaucoma can also be called: Secondary glaucoma; Open angle glaucoma; Chronic glaucoma; Closed angle glaucoma; Congenital glaucoma; Acute glaucoma
Glaucoma is the third most common cause of blindness in the United States.
There are four major types of glaucoma:
Open angle or chronic glaucoma is by far the most common type of glaucoma. In open angle glaucoma, the iris does not block the drainage angle as it does in acute glaucoma. The fine fluid outlet channels within the wall of the eye gradually narrow with time. The disease usually affects both eyes, and over a period of years the consistently elevated pressure slowly damages the optic nerve. Chronic glaucoma has no early warning signs, and the associated loss of peripheral vision occurs so gradually that it may go unnoticed until a substantial amount of damage and vision loss have occurred. The only way to diagnose glaucoma early is through routine eye examinations.
Closed angle or acute glaucoma may occur in persons who were born with a narrow angle between the iris and the cornea (the anterior chamber angle). This is more common in farsighted eyes. The iris may slip forward and suddenly close off the exit of aqueous humor, and a sudden increase in pressure within the eye follows. Symptoms of pain, redness, nausea, and visual loss develop rapidly. Angle closure may be provoked by the use of drops that dilate the eyes in susceptible persons. Attacks may also develop without any obvious triggering event. This is more common in the evening because the eye’s pupils naturally dilate in dim light.
Congenital glaucoma is present at birth, and is the result of defective development of the fluid outflow channels of the eye. Surgery is required for correction. Congenital glaucoma is often hereditary.
Secondary glaucoma is caused by other diseases including some eye diseases (uveitis) and systemic diseases, and by some drugs (corticosteroids).
All four types are characterized by increased pressure within the eyeball, and therefore all of them can cause progressive damage to the optic nerve. Increased pressure occurs when the fluid within the eye (called aqueous humor), which is produced continuously, does not drain properly. The pressure pushes on the junction of the optic nerve and the retina at the back of the eye. This reduces the blood supply to the optic nerve, which carries vision from the eye to the brain. This loss of blood supply causes the individual nerve cells to progressively die. As the optic nerve deteriorates, blind spots develop in the field of vision. Peripheral vision (side vision) is affected first followed by front or central vision. Without treatment, glaucoma can eventually cause blindness.
Risk factors depend on the type of glaucoma. For chronic glaucoma, the risk factors include; age over 40, a family history of glaucoma, diabetes, and nearsightedness. People with a family history of open angle glaucoma have twice the risk of developing open angle glaucoma as those who do not. African-Americans have four times the risk of developing open angle glaucoma as compared to Americans of European decent. It is estimated that 1 to 2% of people over 40 have chronic glaucoma with about 25% of cases undetected.
The risk factors for acute glaucoma are: family history of acute glaucoma, older age, farsightedness, and the use of systemic anticholinergic medications (such as atropine or eye dilation drops) in a high-risk individual. Acute, congenital, and secondary glaucoma are much less common than chronic glaucoma.
There is no prevention for the development of open angle glaucoma. If detected early, further vision loss and blindness may be prevented with treatment. Patients with risk factors for closed angle glaucoma should be evaluated and those at high risk should have laser iridotomy, which will prevent acute attacks.
Careful use of dilating eye drops and systemic anticholinergic medications will minimize the risk of acute attacks in high-risk individuals.
Anyone over 35 years of age should have tonometry (a check of intraocular pressure) and ophthalmoscopy examinations every 2 years. More frequent examination is indicated when a family history of glaucoma is present or in African Americans.
Severe eye pain, facial pain
Loss of vision
Cloudy vision with halos appearing around lights
Fixed, non-reactive pupil
Nausea and vomiting
Gradual loss of peripheral vision
Most people have no symptoms until peripheral visual loss is severe
Blurred or foggy vision
Mild, chronic headaches
Seeing rainbow-colored halos around lights
Sensitivity to light
Redness of the eye
An enlarged cornea
Signs and tests
A physical examination may be non-diagnostic. Intraocular pressure fluctuates, and a single measure may catch it at a low point. Examination of the junction of the optic nerve and the retina with an instrument called an ophthalmoscope is necessary.
A standard ophthalmic examination may include the following:
Intraocular pressure measurement by tonometry
Visual field measurement
Pupillary reflex response
Slit lamp examination
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