Macular Degeneration & Blindness


Macular degeneration, also called Age-related Macular Degeneration (AMD) due to its common occurrence in people over 60, is a frequent form of visual impairment in the elderly but does not result in total blindness. This is because it affects the macular region of the eye which has a dense mass of cone cells, those cells which gauge they eye’s acuity and recognise detail, but few rod cells, the cells which gauge our peripheral sight and visual field. As the retinal and macular regions degenerate, the cone cells can no longer process light and so the central vision decreases but the field of vision remains intact. A person suffering from advanced macular degeneration will still be able to navigate a room without hitting a table or bumping into a wall but will not be able to perform tasks like reading, sewing, or recognising faces because the centre of their vision is dark. This disease is progressive and gradually gets worse overtime. At its worst, however, it only impairs about 35 percent of a person’s total vision because the macula itself only compromises 5 percent of the eye.

Dry and Wet AMD

As the eye ages, small yellow masses called drusens are slowly deposited in the retina, the part of the eye that sends light into the macula. As the debris from the drusens increase, central vision decreases. This is called dry macular degeneration. In early stages of the disease, it may not be entirely noticeable.  Straight lines may seem wavy or fuzzy, colour can seem distorted, spots can appear in central visual regions, but vision is relatively normal. An optometrist can diagnose AMD even in the early stages, however, by using an Amsler grid. This is a box with a black and white grid inside which measures the eye’s level of distortion when looking at straight lines.

Another, less frequent, form of AMD is wet macular degeneration which affects about 10-15 percent of those suffering from AMD. The macula is stationed at the back of the eye near the blood vessels which receive the nerve impulses to send to the visual cortex in the brain. The white part of the eye is the protective layer called the sclera which is separated from the retina by a layer called the choroid. The choroid is a vascular, or vessel-containing, tissue which also connects to the optic disc. When new blood vessels in the choroid degenerate, blood leaks into the retina causing central vision loss.

Who is at-risk for AMD?

Age is the most prominent factor in who will suffer low vision due to AMD and 42 percent of people over 80 with drusens will develop dry macular degeneration. Children can develop juvenile macular degeneration in rare cases, often in the form of other conditions such as Best’s disease, Sorsby’s disease, and Stargardt’s disease.  What about the other 58 percent of those people who do not acquire AMD?  It is thought that some people are predisposed to AMD. Women and smokers are both more likely to experience this type of vision loss than their male and non-smoking counterparts. There is also a genetic component to macular degeneration as there are some genes thought to influence a person’s likelihood of developing AMD in their old age. Health also factors into it. Smoking, direct sunlight without eye-protection and malnutrition are all thought to contribute to whether or not a person will have AMD.

Treatments of AMD

Although AMD is a common handicap among the elderly, there are a number of treatments to slow or temporarily cure the onset of macular degeneration. Lifestyle changes such as not smoking, shielding eyes from the sun, and eating well can be preventative measures. Taking antioxidant vitamins like C, E, and zinc as well as Omega-3 from fish oil can prevent and even slow the disease after it has been diagnosed in some cases. As the disease progresses, however, more drastic medical practices may be employed. Abnormal blood vessels can be temporarily destroyed either by a high-energy laser or by a photodynamic laser. In the first instance, the laser is used to destroy the blood vessels; in the latter, an injection introduces a drug into the bloodstream which the eye’s abnormal blood vessels absorb; at this point the drug must be activated by a cold laser shone into the eye.  Unfortunately, the blood vessels can return and multiple laser courses may be needed. Macular translocation is a more invasive surgery in which the macula is actually moved into a healthier section of the retina. A relatively new development involving a miniature microscope (IMT) can be placed in the eye and improves the daily life of macular degeneration sufferers. Anti-angiogenesis drugs for the slowing of the eye’s production of abnormal blood vessels are also being developed.

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