Macular Degeneration occurs in 2 forms. These are "involutional" (DRY) which usually occurs in people over 50 and "neovascular" (WET). Both forms affect central vision causing loss of the ability to read and recognise faces.
People with macular degeneration usually retain enough peripheral vision to care for themselves and remain active, but reading a clock, a street sign, the destination particulars on a bus even telling the difference between a bus and a truck is difficult without central vision.
Reading, driving, sewing and any tasks that demand fine visual discrimination require a healthy macula. Without it, the world is visible but only in an imprecise way. However, macular degeneration seldom leads to total blindness.
Symptoms of Macular Degeneration
Macular Degeneration is characterised by loss, blurring or distortion of central vision caused by progressive deterioration of the macula, the small central area of the light-sensitive cells making up the eye's retina. A dark grey spot may appear in the central part of vision or the size of an object may appear different for each eye. It is the visual acuity which is most affected.
Although there are no symptoms in the early stages, an ophthalmologist can detect the condition during a medical eye examination before the symptoms appear.
Use of the "Amsler grid" at home can also lead to early detection
(Test your sight with the Amsler
Diagnosis and Treatment
There is help available for people with macular degeneration. Vision aids in the forms of magnifying lenses and reading machines for close work and telescopic lenses for distance can greatly assist many individuals with macular degeneration to continue a relatively normal life. A wide range of vision aids is available from Low Vision Centres but referral by an ophthalmologist is required. Some recently developed drugs are also available to treat (wet)
macular degeneration, see below.
Involutional, atrophic ("dry") Age Related Macular Degeneration (AMD)
Involutional macular degeneration is the technical name for what is often more simply described as "age-related" because it is commonly associated with aging. What happens with age-related macular degeneration is that the macula progressively thins and dries that is, it progressively atrophies as part of the ageing process. Consequently, this condition is also labelled "dry" macular degeneration. This involutional or age-related form is by far the most prevalent form of macular degeneration, accounting for 90 percent of all cases.
Why the macular thins and dries in some older people and not in others is yet not known, although two things appear to be fairly clear. One is that some families seem to have a predisposition to age-related macular degeneration, meaning that family members are more prone to it. If someone in a family has macular degeneration, an ophthalmologist should examine annually all family members over 40. Additionally, there is now clear evidence that smoking can contribute to the development and progress of the condition.
Medical or surgical treatment for age-related (dry) macular degeneration is not yet available, though experimental research is in progress and hopefully treatments will result. However, not only may vision be helped by vision aids but, with appropriate counselling, people can learn to use some of their peripheral vision to help them see more clearly and continue to cope with the practical tasks of everyday life.
The earlier macular degeneration is detected, the better are the chances of maintaining useful vision. Compensation by an unaffected eye often masks early symptoms. When symptoms do appear, they vary.
Exudative or "wet" MD/Neovascular Macular Degeneration
Neovascular macular degeneration is also labelled "wet" macular degeneration because it is fluid from leaking blood vessels in the retina that causes the light-sensitive cells of the macula to sicken and die. This can occur at any age but is still more common as age increases.
Noticeable visual symptoms usually accompany this process. Straight-lines look wavy and later blank spots may appear in your vision. If untreated much of the nerve tissue in the macula may be killed or injured within a few weeks or months. This damage cannot be repaired because nerve cells in the macula do not grow back once they have been destroyed.
Although only a small percentage of people with macular degeneration develop this form, they may make up the majority of those who suffer serious vision loss as a result of macular degeneration.
If leaking blood vessels characteristic of neovascular macular degeneration are detected early enough, treatment by intravitreal injections into the eye can be used. In 95% of cases this treatment results in halting the progression of the disease, and about 40% of people may even experience an improvement in vision.
In some cases, the ophthalmologist may aim a focused beam of laser light at the leaking blood vessels. On contact, the laser light turns into heat and destroys (photocoagulates) the leaking blood vessels. A sophisticated photograph, called a fluorescein angiogram, maps the affected area and allows the ophthalmologist to aim the laser beam precisely.
Although the laser treatment does not restore lost vision, distortion usually disappears and, more importantly, further vision loss is retarded. Recently, laser therapy has been combined with a drug, Visudyne, which helps focus the laser in the macular. Advice should be sought from your ophthalmologist.
As with the more prevalent involutional form of macular degeneration, vision aids can be a great help, as can training in how to make more effective use of peripheral vision.
Does Macular Degeneration run in Families?
For most people with age-related macular degeneration, there is no hereditary predisposition. However, if someone is diagnosed with this condition before the age of 50, there is an increased risk for other family members and they should be encouraged to seek medical advice.
There are several other degenerations of the macula which are more clearly genetic and in which the macula is damaged.
Click here for Genetic Inheritance