The macula is found at the center of the retina where the incoming rays of light are focused. The macula is very important, being responsible for what we see straight in front of us, the vision needed for detailed activities such as reading and writing, recognizing faces, fine work, and our ability to appreciate color.
Macular Degeneration is a condition whereby the delicate cells of the macula become damaged and stop working. We do not know why this is, although it tends to happen as people get older. Vision loss usually occurs gradually and typically affects both eyes at different rates.
What causes macular degeneration?
The root causes are still unknown. There are two forms of age-related macular degeneration, namely "wet" and "dry".
What are the symptoms?
- For many people the visual cells simply cease to function, like the colors fading in an old photograph - this is known as 'dry' degeneration. 70% of patients have this "dry" form, which involves thinning of the macular tissues and disturbances in its pigmentation.
- The other 30% have the "wet" form, which can involve bleeding within and beneath the retina, opaque deposits, and eventually scar tissue. The "wet" form accounts for 90% of all cases of legal blindness amongst macular degeneration patients. The dry form will often begin to convert to wet, with the appearance of abnormal choroidal blood vessels - angiogenesis. The reason why angiogenesis occurs is unknown but it is believed that this additional blood vessel development is somehow caused by deposits being left in the back of the eye. These deposits are similar to age spots on the skin. These new blood vessels are fragile and have a propensity to leak and bleed, eventually forming scar tissue and resulting in irreversible vision loss.
- Different forms of macular degeneration may occur in younger patients. These non-age-related cases may be linked to heredity, diabetes, nutritional deficits, head injury, infection, or other factors.
- Inherited macular degeneration, which appears in some families but not in others, is known as macular dystrophy. Since macular degeneration affects most patients later in life, it is difficult to study successive generations in a family. Recent studies of twins indicate that both genetic and non-genetic factors play important roles in age-related macular degeneration. If several members of a family are sufferers then it is very important that other members have their eyes checked regularly.
- It has been demonstrated that the blue rays of the light spectrum seem to accelerate macular degeneration more than the others. This means that very bright light, such as sunlight or its reflection in the ocean and desert, may worsen macular degeneration. Special sunglasses that block out the blue end of the spectrum may decrease the progress of the disease.
- Hypertension tends to make some forms of macular degeneration worse, particularly in the "wet" form where the retinal tissues are invaded by new blood vessels. The medications used to treat hypertension have not been shown to have any direct effect on macular degeneration, but they may slow progression of the disease by reducing hypertension.
- Any type of smoking or exposure to tobacco smoke can accelerate the development of the "wet" type of macular degeneration.
In the early stages your central vision may become blurred or distorted, with things looking an unusual size or shape. This may happen quickly or develop over several months. You may be very sensitive to light or actually see lights that are not there. People with the advanced condition will often notice a blank patch or dark spot in the centre of their sight. This makes activities like reading, writing and recognizing small objects or faces very difficult.
The formation of new blood vessels and exudates ("drusen") from blood vessels in and under the macula is often the first physical sign that macular degeneration
may develop. In addition, the following signs may be indicative of macular problems and anyone experiencing these symptoms should consult an ophthalmologist immediately:
- The major risk factors: aging, atherosclerosis and hypertension.
- Straight lines appear distorted and, in some cases, the center of vision appears more distorted than the rest of the scene.
- A dark, blurry area or "white-out" appears in the center of vision.
- Color perception changes or diminishes.
The following are NOT known to be linked to macular degeneration: floaters (moving spots caused by debris floating in the vitreous fluid between the lens and the retina); dry eye syndromes; cataracts
Early detection is important because a patient destined to develop macular degeneration can sometimes be treated before symptoms appear and this may delay or reduce the severity of the disease. Furthermore, as we develop better treatments for macular degeneration, whether they are medicinal, surgical, or low vision aids
, those patients diagnosed with macular degeneration can sooner benefit from them.Is there a cure?
At this time there is no known cure for macular degeneration. In some cases, macular degeneration may be active and then slow down considerably, or even stop progressing for many years. There are ways to slow macular degeneration, depending on the type and the degree of the condition. Current treatments fall into three main categories:
What is the usual outcome?
- Nutritional Intervention.
- Surgery. Laser surgery to remove the scar produced by macular degeneration has been successful in about 10% of people with disciform degeneration, mainly the younger patients. If the degeneration is associated with leaking blood vessels in the center of the macula and vision is worse than 20/70 then laser surgery called photocoagulation is recommended. This will not improve vision but generally reduces further vision loss. Unfortunately for most people, the area of degeneration is in the middle of the macula, at its focal point. This means that treatment cannot be given because the scars produced by the laser would make central vision worse rather than better. 'Dry' degeneration cannot be treated by laser.
Retinal transplantation is a new experimental approach to macular degeneration, but will require research to determine its safety and effectiveness.
- Making the most of remaining vision. Low vision aids (such as brighter reading lights, magnifying glasses and more sophisticated devices) and techniques for maximizing the use of peripheral vision are used to help patients adapt better to their loss of central vision.
There is some good news: macular degeneration is not painful, and never leads to total blindness. It is the most common cause of poor sight in people over 60 but never leads to complete sight loss because it is only the central vision that is affected. Macular degeneration never affects vision at the outer edges of the eye, so most sufferers will have enough side vision to get around and keep their independence.
The bad news is that if you have macular degeneration in one eye then it will usually develop in the other also. In the early stages, only one eye may be affected, but as the disease progresses, both eyes are usually affected. Even with a loss of central vision, however, color vision and peripheral vision may remain clear.