What is Age-Related Macular Degeneration?

J.M. Willhite

Age-related macular degeneration (AMD) is a medical condition that adversely affects the retina and impairs an individual’s ability to see properly. There is no cure for AMD; therefore, treatment is centered on slowing the progression of the disease. Approach to treatment is wholly dependent on the presentation of the condition. Since AMD is the leading cause of blindness among people 60 years of age and older, individuals should take preventive measures to reduce their risk for developing this debilitating condition.

Optometrists and ophthalmologists both routinely inspect the macula.
Optometrists and ophthalmologists both routinely inspect the macula.

Located in the back of the inner eye, the retina is considered a relay center that converts light and images entering the eye into signals the brain may interpret. Within the retina is the macula, which gives proper vision its clarity and sharpness. Macular degeneration is a condition that targets the macula and damages its blood vessels. The presentation of age-related macular degeneration may occur in two phases.

Stem cells therapy has shown promise for treating age-related macular degeneration.
Stem cells therapy has shown promise for treating age-related macular degeneration.

The initial phase of the condition is known as dry (non-neovascular) macular degeneration, which weakens the blood vessels and makes them brittle. During this presentation of the disorder, small deposits, called drusen, form beneath the macula and progressively mature and multiply. As the deposits increase, vision becomes blurred and central vision is impaired. As the disorder progresses, wet AMD may develop.

An optometrist may use a variety of tests to evaluate the condition of an individual’s retina and optic nerve.
An optometrist may use a variety of tests to evaluate the condition of an individual’s retina and optic nerve.

Wet (neovascular) macular degeneration involves the regeneration of abnormal blood vessels in place of the brittle, weakened vessels that break down in the presence of dry AMD. Known as choroidal neovascularization, the newly formed vessels seep fluid and blood into the inner eye that accumulates and damages the macula. Of the two forms of AMD, wet macular degeneration is most frequently associated with an increased risk for blindness.

Age-related macular degeneration is one of the top causes of vision loss in people who are over 60 years of age.
Age-related macular degeneration is one of the top causes of vision loss in people who are over 60 years of age.

There is no known cause for the development of age-related macular degeneration. As its name implies, the condition is most prevalent among individuals who are 60 years of age and older. Since the condition is progressive in nature, individuals may develop signs long before marked changes in one’s vision occur. It is important to note that AMD may not cause complete blindness, since peripheral vision usually remains unaffected by the disease.

Age-related macular degeneration often causes blurred or cloudy vision.
Age-related macular degeneration often causes blurred or cloudy vision.

Individuals often remain asymptomatic, meaning they experience no symptoms at all, during the initial onset of AMD. Those who develop dry AMD often experience blurred vision confined to the center of his or her vision field. Also, colors may appear faded and objects may seem hazy and muted. An individual with dry AMD may develop difficulty reading or distinguishing details.

As age-related macular degeneration progresses, additional light may be necessary for reading, working on a computer, or other everyday activities. Blurred vision that was initially confined to the center of the vision field may begin to expand and become darker. Over time, people and objects in the distance may be unrecognizable until the individual gets closer to them.

An optometrist may use a variety of tests to evaluate the condition of an individual’s retina and optic nerve and determine the presence of AMD. After dilating one’s pupils, the doctor may assess the condition of the blood vessels and surrounding membrane. The discovery of the presence of drusen is indicative of dry macular degeneration.

One's vision may also be tested using a tool known as an Amsler grid, which is used to determine how an individual sees line patterns. Individuals with dry AMD usually see wavy lines instead of the printed straight ones. Additional testing may include the administration of a fluorescein angiogram, which uses a camera and special dye to evaluate blood flow in the retina and an optical coherence tomography (OCT) scan that produces three-dimensional images of the retina to assess its condition.

There is no cure for age-related macular degeneration. Treatment is centered on slowing the progression of the disease. Individuals with dry AMD may be instructed to start a regimen consisting of a combination of antioxidants, vitamins, and zinc, known as the Age-Related Eye Disease Study (AREDS) formula. Those diagnosed with wet AMD may be prescribed anti-angiogenesis medication, to delay new blood vessel growth, and other drugs to improve and stabilize his or her vision. Other treatment options for wet AMD may include the use of laser surgery to eliminate the abnormal blood vessels or the application of photodynamic therapy to eradicate blood vessels leaking fluid and blood.

Prognosis for this condition is dependent on the presentation of the disease and treatment approach. Most who are diagnosed with age-related macular degeneration are able to maintain their ability to function and complete routine activities without difficulty. Complications include the necessity of supplemental lighting and a loss of central vision. Individuals with a family history of age-related macular degeneration may be at an increased risk for becoming symptomatic. Additional risk factors include obesity and smoking.

Some people with age-related macular degeneration have no symptoms during the early stage of the disease.
Some people with age-related macular degeneration have no symptoms during the early stage of the disease.

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