Glaucoma is a sight-threatening disease affecting the optic nerve –the direct connection between each eye and the brain. When glaucoma damages optic nerves, areas of blind spots develop in the peripheral vision. As the nerves deteriorate, so does vision. If untreated, blindness eventually occurs. Even with treatment, optic nerve damage cannot be reversed, only stopped.
More than 3 million Americans have glaucoma. It is the second most common cause of blindness in the U.S. and is the leading cause of blindness among African Americans. Elderly people are more at risk to develop glaucoma. The risk increases as an individual’s age increases. Regardless of age or racial heritage, the most significant risk factor for developing glaucoma is an elevated intraocular pressure. Other risk factors include a family history of glaucoma, nearsightedness or farsightedness, eye injury, low blood pressure, diabetes and migraines.
Glaucoma has few early symptoms. Half the people with glaucoma are unaware that they have the condition. The disease progresses slowly and gradually steal the sight. Regular examinations provide the best opportunity for early detection of elevated eye pressure and optic nerve damage. Early identification and immediate treatment of glaucoma is essential for preventing vision loss.
To diagnose glaucoma, the ophthalmologist measures the eye pressure with an instrument called tonometer. Numbing drops are placed to facilitate the test. Normal intraocular pressures is between 10 and 21 mm of mercury. The ophthalmologist inspects the optic nerve for signs of damage. Drops are usually placed in the eye to dilate the pupil. Optical coherence tomography (OCT) is an imaging method that uses light to scan the optic nerves for decreased nerve fiber layer thickness. A visual field test is performed to see if any blank spots are present in the field of vision. The anterior chamber angle, drainage angle inside the eye, is studied with gonioscopy to determine if the glaucoma is open-angle or narrow angle.
There are two major forms of glaucoma. Open-angle glaucoma is the most common, accounting for 70% of all glaucoma patients. Angle-closure glaucoma is the second most common form. Other less common types of glaucoma include Secondary, Normal or Low-tension and Congenital.
Aqueous humor, a clear fluid inside the eye, is refreshed by a continual, precise process of production and drainage that ensures the fluid pressure remains constant. Elevated intraocular pressure occurs when this fluid does not drain properly through the anterior chamber angle. This condition is termed Open-angle glaucoma. Open-angle glaucoma is treated by reducing the amount of fluid produced in the eyeball or by increasing the flow of liquid out of the anterior chamber. This can usually be accomplished with eye drops. These eye medicines are usually effective in control of intraocular pressure and required once or twice daily applications with minimal side effects or discomfort. After reviewing your medical history and glaucoma diagnostic tests, the ophthalmologist will select the eye drops that are best suited for your glaucoma treatment.
Laser trabeculoplasty is an alternative treatment for patients whose intraocular pressure is adequately controlled with eye drops or who are unable to use eye drops or may choose not to. This procedure uses precise laser pulses to stimulate specialized cells in the drainage angle in the eye to improve their performance.
Elevated intraocular pressure can also be treated by incision surgery with a procedure termed trabeculectomy. The eye surgeon creates a flap in the sclera (white tissue) and makes a reservoir in the conjunctiva (the transparent membrane covering the eye). Excess aqueous fluid drains out of the eye into the reservoir and is absorbed by blood vessels surrounding the eye.
An alternative glaucoma surgical procedure is aqueous shunt. The shunt is a small tube inserted through sclera and directs excess fluid into the conjunctiva where it is absorbed.
Narrow angle or angle closure glaucoma is a form glaucoma where the iris of the eye bowing forward, blocking fluid from flowing out of the anterior chamber angle. This angle closure attack causes pressure inside the eyeball to rapidly increase. Closed-angle glaucoma is considered a medical emergency and must be treated immediately. The longer eye pressure remains critically high, the greater the risk of permanent vision loss. Asian descendants and farsighted individuals are more susceptible to develop angle-closure glaucoma. Laser iridotomy is used to treat acute angle closure glaucoma. A laser opening is created in the iris to improve the flow of aqueous to the drainage angle. Laser iridotomy is also recommended to treat very narrow drainage angle to prevent attack of angle closure.
Optic nerve damage and visual field loss can occur in individuals with normal intraocular pressure. Normal or Low-tension glaucoma is treated in the same manners as open angle glaucoma with target pressure significantly lower to stop optic nerve and visual field progression.
Tumors, trauma and vascular abnormalities associated with diabetes can also cause glaucoma. If glaucoma is a complication of a disease, eye condition or medication, it’s referred to as Secondary glaucoma. Long-term use of steroid medications has been associated with glaucoma, for example.
Congenital glaucoma, the rarest form of the disease, occurs in infants and young children whose eye fluid drainage system fails to develop normally.
Advances in the diagnoses and treatments of glaucoma have improved the care of many patients. Most patients can expect preservation of sight and quality of life.
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