AMD is a common eye condition and a leading cause of vision loss among people aged 50 and older. It causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp, central vision, which lets us see objects that are straight ahead.
In some people, AMD advances so slowly that vision loss does not occur for a long time. In others, the disease progresses faster and may lead to a loss of vision in one or both eyes. As AMD progresses, a blurred area near the center of vision is a common symptom. Over time, the blurred area may grow larger or you may develop blank spots in your central vision. Objects also may not appear to be as bright as they used to be.
AMD by itself does not lead to complete blindness, with no ability to see. However, the loss of central vision in AMD can interfere with simple everyday activities, such as the ability to see faces, drive, read, write, or do close work, such as cooking or fixing things around the house.
Wet And Dry Forms of Macular Degeneration
The dry form is more common than the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry AMD. The wet form of the disease usually leads to more serious vision loss.
Dry macular degeneration (non-neovascular)
Dry AMD is an early stage of the disease and may result from the aging and thinning of macular tissues, depositing of pigment in the macula or a combination of the two processes.Dry macular degeneration is diagnosed when yellowish spots known as druse begin to accumulate in and around the macula. It is believed these spots are deposits or debris from deteriorating tissue.Gradual central vision loss may occur with dry macular degeneration but usually is not nearly as severe as wet AMD symptoms. However, dry AMD through a period of years slowly can progress to late-stage geographic atrophy (GA) — gradual degradation of retinal cells that also can cause severe vision loss.
Wet macular degeneration (neovascular)
In about 10 percent of cases, dry AMD progresses to the more advanced and damaging form of the eye disease. With wet macular degeneration, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive retinal cells, which die off and create blind spots in central vision.Choroidal neuvasculisation (CNV), the underlying process causing wet AMD and abnormal blood vessel growth, is the body's misguided way of attempting to create a new network of blood vessels to supply more nutrients and oxygen to the eye's retina. Instead, the process creates scarring, leading to sometimes severe central vision loss.
What are the risk factors for macular degeneration?
- Aging: The prevalence of AMD increases with age, approximately one in 14 people over the age of 40 has some degree of macular degeneration. For those over 60, the rate is one in eight (12.5 percent); and for seniors over age 80, one in three (33 percent) has AMD.
- Obesity and inactivity: Overweight patients with macular degeneration had more than double the risk of developing advanced forms of macular degeneration compared with people of normal body weight,
- Heredity: Recent studies have found that specific variants of different genes are present in most people who have macular degeneration. Studies of fraternal and identical twins may also demonstrate that heredity is a factor in who develops AMD and how severe it becomes.
- Smoking: Smoking is a major AMD risk factor.
- Drug side effects: Some cases of macular degeneration can be induced from side effects of toxic drugs.
How is macular degeneration treated?
Wet macular degeneration: Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a permanent cure for wet AMD. The disease and loss of vision may progress despite treatment.Laser surgery in the form of photocoagulation is used to destroy the fragile, leaky blood vessels. A high energy beam of light is aimed directly onto the new blood vessels to eradicate them, preventing further loss of vision. However, laser treatment may also destroy some surrounding healthy tissue and some vision. Because of this, only eyes with new vessels away from the exact center of the vision can be treated. This represents only a small proportion of patients with AMD. Laser surgery is only effective in halting or slowing visual loss if the leaky blood vessels have developed away from the fovea, the central part of the macula. Even in treated cases, the risk of new blood vessels recurring after treatment is significant and further or other treatment may be necessary.Photodynamic therapy uses a drug called verteporfin that is being injected into a vein of the arm. A light of a specific wavelength is then directed into the eye to activate the drug adhering to the blood vessels in the eye. The activated drug destroys the new blood vessels and leads to a slower rate of vision decline. Photodynamic therapy may slow the rate of vision loss. It does not stop vision loss or restore vision in eyes already damaged by advanced AMD. Treatment results often are temporary. Retreatment may be necessary.
Dry macular degeneration:Right now, there is no way to treat the dry form of AMD. However people with lots of drusen or serious vision loss might benefit from taking a certain combination of nutritional supplements. A large study found those people may slow their dry AMD by taking these vitamins and minerals daily:
- Vitamin C (500 mg)
- Vitamin E (400 IU)
- Lutein (10 mg)
- Zeaxanthin (2 mg)
- Zinc (80 mg)
- Copper (2 mg)
What are complications of macular degeneration?
Progression to wet macular degeneration is the main complication of dry age-related macular degeneration. At any time, dry macular degeneration can progress to the more severe form of the disease called wet macular degeneration, which may cause rapid vision loss. There is no accurate way to predict who will eventually develop wet macular degeneration.Other eye diseases such as cataracts, glaucoma, retinal detachment, or dry eyes are not complications of macular degeneration. Patients with macular degeneration can, however, develop these or other eye diseases and people with these conditions can also develop AMD concurrently.