What exactly is macular degeneration?
As the eye looks straight ahead, the macula is the point of the retina upon which the light rays meet as they are focused by the cornea and the lens of the eye. Similar to the film in a camera, the retina receives the images that come through the lens. If the macula is damaged, the central part of the images are blocked as if a blurred area had been placed in the centre of the picture. The images around the blurred area may be clearly visible.
The retina is the delicate layer of tissue that lines the inside wall of the back of the eye. The macula is a very small area in the centre of the retina. In size, the macula is about the same as a capital “O” in the type of this pamphlet. This small area is responsible for our central “straight ahead” sight used for reading and other fine tasks.
Macular degeneration is damage or breakdown of the macula. The eye still sees objects to the side, since “peripheral” vision is usually not affected. For this reason, macular degeneration alone does not result in total blindness. However, it can make reading or close work difficult or impossible without the use of special low vision optical aids.
Although macular degeneration most often occurs in older people, ageing alone does not always result in central visual loss. Nevertheless, macular degeneration is the leading cause of impairment of reading and fine “close-up” vision in most countries.
Causes
The most common form of macular degeneration is called dry macular degeneration. This form accounts for 90% of all cases, and is associated with ageing. It is cause by a breakdown of thinning of the tissues in the macula.
About 10% of macular degeneration falls into a category called exudative macular degeneration. Normally, the macula is protected by a thin tissue that separates it from very fine blood vessels nourishing the back of the eye. Sometimes these blood vessels break or leak and cause scar tissue to form. This often leads to the growth of new abnormal blood vessels in the scar tissue. These newly formed vessels are especially fragile. They rupture easily and may leak. Blood and leaking fluid destroy the macula and cause further scarring. Vision becomes distorted and blurred, and dense scar tissue blocks out central vision to a severe degree.
Other types of macular degeneration are inherited and are not associated with the ageing process. Occasionally injury, infection, or inflammation may also damage the delicate tissue of the macula. If only one eye is affected, macular degeneration is hardly noticeable in the beginning stages, particularly when the other eye is normal. This condition often involves one eye at a time, so it may be some time before a patient notices visual problems.
Symptoms
Macular degeneration can cause different symptoms in different people. Sometimes only one eye loses vision while the other eye continues to see well for many years. If both eyes are affected, however, reading and close-up work may become extremely difficult. Macular degeneration alone does not cause total blindness. Since side vision is usually unaffected, most people can take care of themselves quite well. Colour vision may become dim.
Medical and surgical treatment
There is no cure for the most common form of macular degeneration. However, ophthalmic laser has been used to retard the spread of the less common exudative form, but only if this treatment is applied in the very early stages of the condition. In this treatment, a focused intense beam of laser light is used to seal off leaking membranes and destroy new blood vessels. This reduces further loss of vision from progressive scarring of the macula and the surrounding retina.
Other options for treatment are:
- Surgical removal of new vessel membranes
- Photodynamic therapy (PDT)
Who can treat macular degeneration?
An ophthalmologist is the medical doctor who is educated, trained, and licensed to provide total care of the eyes including the diagnosis and treatment of macular degeneration. Your ophthalmologist will discuss the relevant treatment modalities with you.
Optical aids and lighting
Low vision optical aids often improve vision for people with macular degeneration. Many different types of magnifying devices are available. Spectacles, hand or stand magnifiers, telescopes, and closed circuit television for viewing objects are some of the available resources. Aids are either prescribed by your ophthalmologist or by referral to a low vision specialist or center. Bright illumination properly directed for reading and close work are often beneficial. Special lamps can also be helpful. Books, newspapers and other items available in large print offer further help.
A patient with macular degeneration can be helped. Fortunately, visual aids are available to assist many patients in leading a comfortable and relatively normal life. With these devices and proper motivation, people with visual loss can often read, do modified close-up work, and continue to take care of themselves.
If you are over age 50 or if your family has a history of retinal problems, you should have your eyes checked periodically for signs of eye problems like macular degeneration. Early detection and subsequent treatment, if indicated, may help prevent additional visual loss.
If you have additional questions or would like any further information, contact your ophthalmologist.