Human eye has various important parts like Cornea, Pupil, Iris, Lens and Retina. The macula is located in the center of the retina, the light-sensitive tissue at the back of the eye. The retina instantly converts light, or an image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain. When the cells of the macula deteriorate, images are not received correctly. In early stages, macular degeneration does not affect vision. Later, if the disease progresses, people experience wavy or blurred vision, and, if the condition continues to worsen, central vision may be completely lost. People with very advanced macular degeneration are considered legally blind. Macular Degeneration is the leading cause of vision loss, more than cataracts and glaucoma combined.
Macular degeneration is classified as:
Pathophysiology
The dry form is more common than the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry AMD. The less common wet AMD usually leads to more serious vision loss.
Dry AMD causes changes of the retinal pigment epithelium, typically visible as dark pinpoint areas. The retinal pigment epithelium plays a critical role in keeping the cones and rods healthy and functioning well. Accumulation of waste products from the rods and cones can result in drusen, which appear as yellow spots. Areas of chorioretinal atrophy (referred to as geographic atrophy) occur in more advanced cases of dry AMD. There is no elevated macular scar (disciform scar), edema, hemorrhage, or exudation.
Dry AMD has three stages, all of which may occur in one or both eyes:
Wet AMD occurs when new abnormal blood vessels develop under the retina in a process called choroidal neovascularization (abnormal new vessel formation). Localized macular edema or hemorrhage may elevate an area of the macula or cause a localized retinal pigment epithelial detachment. Eventually, untreated neovascularization causes a disciform scar under the macula.
Symptoms
Dry macular degeneration symptoms usually develop gradually and without pain. They may include:
What causes macular degeneration?
Though macular degeneration is associated with aging, there is genetic component to the disease. A strong association between development of AMD and presence of a variant of a gene known as complement factor H (CFH) is observed. This gene deficiency is associated with almost half of all potentially blinding cases of macular degeneration.
Other investigators have found that variants of another gene, complement factor B, may be involved in development of AMD.
Specific variants of one or both of these genes, which play a role in the body's immune responses, have been found in 74 percent of AMD patients who were studied. Other complement factors also may be associated with an increased risk of macular degeneration.
Oxygen-deprived cells in the retina produce a type of protein called vascular endothelial growth factor (VEGF), which triggers the growth of new blood vessels in the retina.
The normal function of VEGF is to create new blood vessels during embryonic development, after an injury or to bypass blocked blood vessels. But too much VEGF in the eye causes the development of unwanted blood vessels in the retina that easily break open and bleed, damaging the macula and surrounding retina.
Risk Factors
The biggest risk factor for Macular Degeneration is age. Your risk increases as you age, and the disease is most likely to occur in those 55 and older.
Other risk factors include:
Diagnosis
AMD is detected during a comprehensive eye exam that includes:
What Treatments Are Available for Macular Degeneration?
There’s no cure for macular degeneration. Treatment may slow it down or keep you from losing too much of your vision. Your options might include:
Important Reminder: This information is only intended to provide guidance, not a definitive medical advice. Please consult eye doctor about your specific condition. Only a trained, experienced board certified eye doctor can determine an accurate diagnosis and proper treatment.
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