What is Macular Degeneration?
Macular degeneration is a disorder that affects central vision – what you see directly in front of you as opposed to your peripheral or side vision. The macula is the central portion of the retina, the paper-thin tissue at the back of the eye where light-sensitive cells send visual signals to the brain, and is responsible for detailed vision.
Macular degeneration occurs when the central part of the retina deteriorates. Age-related macular degeneration (AMD or ARMD) is the most common eye disease and is in fact the leading cause of visual impairment and blindness in the United States in people over the age of 50.
Damage to the macula results in the development of blind spots and blurred or distorted vision and can hamper your ability to perform basic activities of daily living such as reading and driving.
Types of Macular Degeneration
Dry Macular Degeneration
Dry macular degeneration is the early stage of the disease. It may be caused by the aging and thinning of the macular tissues, the deposition of pigment in the macula, or by a combination of the two processes. Yellowish spots known as drusen begin to accumulate from these deposits or from the debris from deteriorating tissue, and this occurs primarily in the area of the macula. Loss of central vision may occur very gradually but can be as serious as the wet neovascular form of AMD.
Wet Neovascular Macular Degeneration
Approximately, 10% of dry AMD cases will progress to a more severe, advanced form of eye disease known as wet macular degeneration. Wet macular generation occurs when new blood vessels grow (neovascularization) beneath the retina and leak blood and fluid into the surrounding tissue.
The leakage of blood and fluid causes permanent damage to the light-sensitive retinal cells. These cells then die off and blind spots are created in the central vision. During the process of neovascularization, the body attempts to create a new network of blood vessels to supply more nutrients and oxygen to the eye's retina. This process fails and instead creates scarring that leads to a loss of central vision.
Wet forms of macular degeneration are further classified into two general sub-types – classic and occult. Classic choroidal neovascularization (CNV) is usually associated with severe vision loss. It occurs when blood vessel growth and scarring has very clear, delineated outlines observed beneath the retina. Occult neovascularization produces less severe vision loss and new blood vessel growth beneath the retina is not as distinctive and leakage is less obvious.