Macular degeneration (age-related macular degeneration (AMD)), the leading cause of severe vision loss in elderly over 60, occurs when the small central portion of the retina, the macula, deteriorates. The retina is the light-sensing nerve tissue at the back of the eye. AMD can be a source of significant visual disability.
AMD is classified into two main types:
1. Dry form – it is characterized by the presence of yellow deposits, the drusen, in the macula. The latter can increase in number and grow in size leading to a dimming or distortion of vision when reading. In more advanced stages there is also a thinning of the light-sensitive layer of cells in the macula leading to atrophy, or tissue death. In the atrophic form of dry AMD patients may have blind spots in the center of their vision. In the advanced stages, patients lose central vision.
2. Wet form – it is characterized by the growth of abnormal blood vessels from the choroid underneath the macula, which is termed as choroidal neovascularization. These blood vessels leak blood and fluid into the retina, causing distortion of vision which makes straight lines looking wavy, as well as blind spots and loss of central vision. Finally these abnormal blood vessels and their bleeding form a scar, leading to permanent loss of central vision.
Most AMD patients have the dry form and can lose some form of central vision. However, the dry form of AMD can lead to the wet form.
It is very important for patients with AMD to monitor their eyesight carefully and consult their eye doctor regularly.
It is the leading cause of severe vision loss in adults over age 60. AMD may be hereditary passing on from parents to children.
High blood pressure, high cholesterol, obesity, smoking, and being light skinned, female, and having a light eye color are also risk factors for AMD.
Symptoms of AMD
In its early stages, macular degeneration may not have symptoms and may be unrecognized until it progresses or affects both eyes. The first sign of macular degeneration is usually a dim, blurry spot in the middle of your vision. This spot may get bigger or darker over time.
Symptoms of AMD include:
- Dark, blurry areas in the center of vision
- Diminished or changed color perception
AMD can be detected in a routine eye exam. One of its most common early signs is the presence of drusen, tiny yellow deposits under the retina, or pigment clumping. When looking at an Amsler grid, a pattern of straight lines that resemble a checkerboard, some of the straight lines may appear wavy, or you may notice that some of the lines are missing. These can be signs of AMD.
If AMD detected, you may have a procedure called angiography or an OCT. In angiography, a dye is injected into a arm vein. Photographs are taken as the dye reaches the eye and flows through the blood vessels of the retina. If there are new vessels or vessels leaking fluid or blood in the macula, the photographs will show their exact location and type. OCT is able to see fluid or blood underneath the retina without using dye.
Early detection of AMD is very important because there are treatments delaying or reducing the severity of the disease.
Optical Coherence Tomography (OCT) 光學相干斷層掃描