Age-Related Macular Degeneration (AMD) is a disease of the elderly in which there is progressive loss of retinal cells, resulting in loss of central vision. It is one of the leading cause of blindness affecting those 50 years or older. There are 2 main types of AMD; Dry AMD and Wet AMD
Dry AMD is the more common form of AMD. There are yellow discrete deposits on the retina layer which represent deposition of waste material beneath the retina layer. This leads to gradual loss (atrophy) of the retinal cells, resulting in a slowly progressive loss of central vision.
Wet AMD is also known as exudiates or neovascular AMD. Wet AMD may arises from an area of pre-existing dry AMD. In areas of retina damage, there may be more proteins promoting blood vessel growth. This abnormal, small blood vessels, growing in the layer beneath the retina in the macula. They may leak fluid, lipids and protein, resulting in disruption of the normal structure of the retina. In more adverse conditions there may be bleeding beneath the retina. If it is not treated properly, scar tissues form under the macula and central vision is permanently destroyed.
Blurring of vision– The most common symptoms of dry AMD is gradually progressive blurring of vision. Usually more lights is required to see things clearer and color contrast is not as good as before. Activities such as reading become increasingly more difficult.
Loss of central vision– As dry AMD progresses, a blurred area in the center of vision forms and this blurred spot can increase in size. There may even be a dark spot in the vision.
Distorted vision – Distorted vision or metamorphopsia, occurs when a grid of straight lines appears wavy and parts of the grid may appear blank: Patients often first notice this when looking at tiles in their home.
Difficult night vision– Slow recovery of visual function after exposure to bright light
- Cardiovascular Risk Factors like (Hypertension, Diabetes and Ischaemic Heart Disease)
- Low Dietary intake of Vit A, C, E and Zinc
- Low Dietary intake of Lutein and omega3 fatty acids.
How is AMD diagnosed?
Please see an ophthalmologist if you have the above symptoms. An ophthalmologist can diagnose this by examining the macula after the pupils are dilated.
Home test for AMD
Use a grid to test yourself for AMD. You may use the tiles on your walls at home.
Hold the Amsler Grid below at eye level at a comfortable reading distance. If you wear any type of reading lenses, wear them during this test. Cover one eye at a time, and focus on the centre dot. If you see wavy or fuzzy lines, or if certain squares are missing or appear blurred, you may be displaying symptoms of AMD.
This test is not a substitute for regular eye tests carried out by an optometrist or ophthalmologist, which are vital in detecting AMD and other eye diseases early.
To confirm the wet form of AMD, some test may be performed.
Optical Coherence tomogram (OCT) –This produces cross-sectional images of the retina with good resolution. The technology precisely defines the location and nature of the changes in the retina and and evaluates the thickness of the retina and surrounding structures. These allow detection of fluid, lipid or protein deposit in the retina tissue. OCT provides important information on CNV membranes that are components of AMD.
Fundus fluorescein angiogram (FFA) and Indocyanine Green ( ICG) – A dye is injected into the arm vein during a FFA and ICG and the flow of the dye through the retina is photographed. The dye will allow the detection of blood vessels that are leaking.
Can AMD be treated?
Currently there is no known prevention or treatment for dry AMD.
Recent studies on AMD by the age-related eye disease study group (AREDS) showed that taking vitamin C, vitamin E, zinc and copper, may slow the progression of dry AMD.
Treatments are available for treating wet AMD.
- Anit-VEGF therapy
The stimulus for the growth of abnormal new vessels is the vascular endothelial growth factor (VEGF). By blocking the action of VEGF, the growth and activity of the blood vessels can be potentially be stopped. There are different drugs available. Pegaptanib sodium (Macugen) and ranibizumab (Lucentis) are FDA-approved drugs which can be injected into the eye for it to take action. At least 3 injections given every 4-6 weeks are required and some patients may require additional treatments during the follow-up period.
- Thermal laser photocoagulation
Thermal laser is applied to the abnormal blood vessels. This is useful in about 15 – 20% of patients who have the abnormal blood vessels located away from the centre of the macula (fovea).This treatment is not used for treating areas on the fovea ( the most sensitive part of the retina). If the fovea is treated with thermal laser, there will be immediate and permanent loss of central vision.