The central portion of the retina directly opposite the lens, is called the macula. It enables us to see fine detail and color.
In macular degeneration, the light â€“ sensing cells of the macula malfunction and may over time cease to work. Macular degeneration occurs most often in people over 60yrs old, in which case it is called Age Related Macular Degeneration (ARMD). Less commonly are several hereditary formsÂ of macular degeneration, which usuallyÂ affect children or teen-agers.
With increased longevity worldwide, macular degeneration is the leading cause ofÂ blindness. A study done by National Eye InstituteÂ showed that one out of five people between the ages ofÂ 65 to 74. One of three people over age 75 in this country will suffer some visual impairment due to Macular Degeneration.
What are the types of ARMD ?
The â€œdry â€ form of ARMDÂ develops and progress slowly over a period ofÂ 5 â€“ 10 years or longer. The less prevalent, â€œwetâ€ type ofÂ Â ARMD is characterized by the ingrowth of new blood vessels from the choroid. â€œWetâ€ ARMD progresses much more rapidly, over a period of weeks or months, and usually results in legal blindnessin in the central portion of the visual field.
How do you evaluate ARMD?
Clinical examination, coupled with fluorescein angiography, optical coherence tomography and in some cases, indocyanine green angiography are the tests useful in finding out the type ofÂ ARMD, its prognosis and outcome.
If I develop â€œwetâ€ orÂ â€œdryâ€ ARMD in one eye, will it eventually affect the opposite eye?
Probably. The fellow eye is at high risk of following suit, but the timing can vary significantly from person to person.
What are the risk factors associated with ARMD ?
The strongest risk factors are :
- The incidence of all forms of ARMD rises steeply with advancing age. In one large study, ARMD increased from approximately 4% of individuals at 43 to 54 years of age, to 23% in those 75 years or older.
- Pigmentary changes in the macula is considered to be diagnostic of early atrophic ARMD.
- The incidence of both â€œwetâ€ and â€œdryâ€ ARMD is strongly correlated a history of smoking.The degree of risk is proportional to the amount of cigarette consumption.
- Genetic factors. Several studies have demonstrated a high rate of concordance in the development of ARMD among twins, particularly among identical twins. In family-based studies, the likelihood of developing ARMD is nearly 20 times higher if one or both parents have ARMD. It is highly likely that one or more gene alterations carried by the affected individual increase the susceptibility in his/her offspring.
How does diet influence macular degeneration ?
Several studies now indicate that diets rich in greenÂ leafy vegetables, such as spinach, chard and mustard greens, can reduce the risk of ARMD. These and other vegetables are rich in certain pigmentsÂ known as carotenoids. Among these, lutein and zeaxanthin are two that are highly concentrated in the macula where they may have effects that protect RPE and / or retinal cells from injury caused by the formation of peroxides and other toxicÂ products of the visual cycle. Lutein and zeaxanthin are now widely available as dietary supplements ; however, their efficacy when consumed in this form has not been well studied.
Have vitamins and other nutritional supplements been shown to be effective as treatments for ARMD?
There have been at least five published trials that have tried to determine whether dietary supplements, such as vitamins A,C, E or zinc can arrest or prevent the development of ARMD.Thus far, the results from these small scale studies have not been encouraging. However, new data from a much larger study called the Age-Related Eye Disease Study (AREDS) indicates that dietary supplementation with 500 mg of vitamin C, 400IU of vitamin E, 15 milligrams of beta-carotene and 80 milligrams of zinc (as zinc oxide) can reduce the risk of developing advanced ARMD by approximately 25%.
What are the Treatments for Macular Degeneration ?
20 years back, laser photocoagulation was used for the first time to treat ARMD. For the last 5 years, newer treatments, which are more effective, are coming up. The most commonly applied clinical approach to Age Related Macular DegenerationÂ which in some cases can slow the progression of the disease, but does not restore already lost vision are variable. This is possible with special laser called Photodyanamic therapy. Injections like Lucentis, avastin andÂ newer drugs inside the eye is also possible.Â Â Â Â