What is ARMD?
ARMD is a disease caused by the progressive degeneration of the macula. There are two forms of ARMD, the dry form and the wet form.
Dry ARMD is characterized by the presence of small, round yellow deposits that are found in the retina and known as drusen. Drusen is composed mainly of fats and proteins due to an accumulation of waste products from cellular activity. A few small drusen may not cause changes in vision; however as they grow in size and increase in number, dimming or distortion of vision may start to be apparent. In advanced stages of dry macular degeneration, there is also a thinning of the light-sensitive layer of cells in the macula leading to atrophy, or tissue death. This atrophic form of dry macular degeneration will develop blind spots in the center of their vision.
Wet ARMD only develops in people who already have dry ARMD. This form of ARMD is called wet or exudative ARMD because of the growth of small abnormal blood vessels that leak blood or fluid into the macula, causing hemorrhage or swelling. The onset of wet ARMD can be very sudden, causing severe damage of vision within days. This form of ARMD is responsible for 90% of severe central vision loss.
There are a number of risk factors that may be responsible for the onset of this disease. The known risk factors are: age, family history, smoking, sex (women>men) and race. This disease of the macula is usually seen to occur after the age of 50 and mainly after age 65. ARMD is twice as prevalent among Caucasians as among black people, while Asians and Hispanics fall somewhere between. Studies have shown that ARMD increases four-fold if a close family member has the disease. It has also shown that smokers are three times likely to develop dry ARMD than nonsmokers. The other probable risk factors that can lead to this disease are: poor diet of fruits and vegetables, excessive exposure to bright light, obesity, possessing light iris colour, and the presence of other health diseases.
Wet ARMD Treatment
- Injections - An anti-VEGF injection is the first line of treatment for wet ARMD. The reason why this is the modality of choice is because it has the potential for a patient to gain vision. Wet ARMD abnormally contains high levels of vascular endothelial growth factor to help promote the growth of new leaky blood vessels. Anti-VEGF injection therapy blocks the growth of these abnormal vessels. This treatment usually requires the need for monthly multiple injections to prevent re-occurrence.
- Photodynamic therapy - Photodynamic therapy involves precise laser treatment on abnormal blood vessels. The drug Verteporfin is injected into the vein where it will travel to the eye to tag any new abnormal blood vessels. A laser beam is then used to activate the drug. Once activated, the drug will regress the new blood vessels and slows the rate of vision loss.
- Laser surgery - Laser is an old treatment modality that is still used for certain cases of wet ARMD. A thermal laser is aimed into the eye to destroy these abnormal blood vessels. This treatment is likely to be used when blood vessel growth is limited to a compact area that can easily be targeted and that is away from the center of the macula. Laser treatment therapy will also destroy normal retinal tissue that is next to the abnormal vessels. When this occurs a scar will result from it and will end up creating a blind spot in an individual’s visual field.
Dry ARMD Treatment
Currently there is no proven treatment for early ARMD. Preventative measure can be used to try to slow down the progression of the disease. Those who have signs of early ARMD can adopt certain habits such as: exercise, avoiding smoking and eating nutritious green leafy vegetables and fish to help sustain usable vision.
Intermediate and late ARMD
Studies have shown that daily intake of certain high-dose vitamins and minerals can slow progression of the disease in people who have intermediate or late ARMD.
The first AREDS trial showed that a combination of vitamin C, vitamin E, beta-carotene, zinc, and copper can reduce the risk of late ARMD by 25 percent. The AREDS2 trial tested whether this formulation could be improved by adding lutein, zeaxanthin or omega-3 fatty acids. The AREDS2 trial found that adding lutein and zeaxanthin or omega-three fatty acids to the original AREDS formulation (with beta-carotene) had no overall effect on the risk of late ARMD. However, the trial also found that replacing beta-carotene with a 5-to-1 mixture of lutein and zeaxanthin may help more to reduce the progression of ARMD.
What are the Symptoms?
The most common symptoms are:
- Need for more light when reading
- Loss of contrast
- Distortion on straight lines (metamorphopsia)
- Loss of visual acuity, manifested as difficulty recognizing faces or distinguishing letters on a page
- Diminished colour perception
- Blurry or dark spots (scotoma) in the central visual field