Age-related Macular Degeneration
The retina is a tissue that lines almost the entire inside of the eye. It is a very specialized tissue that collects light information and transmits it to the brain providing us with vision. The macula is a small portion of the retina at the back of the eye that is responsible for central vision and gives us our fine detailed vision and color perception. Age related macular degeneration (ARMD) is a condition that affects the underlay beneath the retina at this center vision area. As the disease progresses, the retinal tissue itself can become affected resulting in vision problems. This can cause blurry patches and distortion in your center vision which can make reading and fine tasks very difficult. In its most sever e form, it can wipeout the center vision area such that one cannot recognize faces or read. ARMD does not cause total blindness. Peripheral (side) vision is not affected by ARMD.
ARMD is commonly divided into 'dry' and 'wet' forms. These are not two distinct conditions, they are actually a spectrum of the same disease. Everybody with ARMD has the dry form initially and it always affects both eyes. However, most people with early dry ARMD have excellent vision and would be unaware of the condition unless detected by an eye doctor. Dry ARMD can remain mild with reasonable vision for many years, or it may gradually progress to atrophy – a thinning out of the underlay beneath the retina. This can cause severe impairment of central vision.
Wet ('exudative') ARMD occurs when abnormal blood vessels develop in the underlay beneath the retina due to weaknesses of that underlay from the dry ARMD changes. The abnormal vessels can leak causing fluid collection in the retina ('swelling' or 'edema') or they can bleed into the retina. The development of wet ARMD usually results in a rapidly progressive severe loss of central vision unless it is detected and treated. Most people with dry ARMD never progress to wet ARMD, but those who do are at risk of severe vision loss. Wet ARMD can develop in one or both eyes, usually not at the same time. Early detection and treatment results in better vision outcomes.
Risks factors for ARMD
Several risk factors are known including genetics, increasing age, smoking, poor nutrition, UV light exposure, high blood pressure.
Symptoms of ARMD
In its early stages there may be no symptoms at all. One eye may be affected more than the other, so it is important to cover either eye and check each separately. Straight lines may look crooked, warped or distorted. There may be dark or blank patches of vision near center. When reading, the words may be blurred or letters may be missing or seem to jump.
Diagnosing ARMD
A regular eye exam is important. Even prior to developing symptoms, and eye doctor can detect retinal changes by examining the retina with special lenses and retinal photographs. Advanced retinal imaging with optical coherence tomography (OCT), fundus autoflourescence, and fluorescein angiography can be useful in more detailed evaluation of the degree of macular degeneration.
Treatment of ARMD
Lifestyle modification may slow progression of macular degeneration - don't smoke, protect eyes from ultraviolet light with hats and proper eyewear, and maintain a healthy balanced diet rich in pigmented fruits and vegetables.
The Age Related Eye Disease study (AREDS) found that in patients with moderate dry ARMD, regular supplements with a combination of Vitamin C, E, beta-carotene, and Zinc (AREDS formula) resulted in a 25% reduction in developing advanced ARMD. Beta-carotene is known to increase risk of lung cancer in smokers and exsmokers and is not recommended in that setting. There are many available over the counter vitamin preparations of the 'AREDS formula'. More recently the AREDS 2 results have been reported which should result in new formulations being available. This study showed benefit to adding Lutein and Xeaxanthin, and removing the beta–carotene.
Treatment of Wet ARMD
There have been tremendous improvements in treating wet ARMD over the past 15 years.
Laser treatment can be used to cauterize the abnormal blood vessels but this leads to a scar and blind spot where the laser was performed. There are few select instances where this can be an effective treatment to preserve central vision.
PDT (photodynamic therapy) combines a light activated drug, infused intravenously, and a nonthermal laser to activate the drug beneath the retina. This can stabilize wet ARMD but with limited vision results.
AntiVEGF therapy is currently the treatment of choice for most people with wet ARMD. VEGF(vascular endothelial growth factor) is a chemical made by the body. It is an important factor in the development of abnormal vessels beneath the retina. AntiVEGF treatment is provided by injecting a VEGF blocking drug into the eye (intravitreal injection). This seals off the abnormal vessels, eliminating retinal swelling and reducing the risk of further bleeding. This treatment is very effective in stabilizing wet AMD, preventing further loss of vision and often results in moderate recovery of vision, although vision does not usually recover back to normal. Treatments are initially provided on a monthly interval with 3 monthly injections as an initial loading phase after which treatments intervals are modified based on individual response. When the condition seems stabilized, treatment can be stopped only if there is very close ongoing monitoring as recurrence of wet ARMD is common after stopping treatment. Please refer to the separate information page for further details about antiVEGF therapy.
Low Vision Aids
Despite our many advances in treatment, some people still develop severe central vision loss from ARMD. Varous magnifying aids, large print books, computerized devices and other practical tools can help people with low vision make the most out of their limited vision. The CNIB is a good resource for low vision aids and counseling.