Macular degeneration is a progressive eye condition in which the macula (the central part of the retina) is damaged, causing gradual loss of central, detailed vision.
Central vision allows us to see the fine details when we look directly at something and is necessary for driving, reading, recognising faces and doing detailed work such as sewing.
The retina is the light-sensitive membrane at the back of the eye which functions like the film in a camera. If the film is warped or damaged, it will not record the image that is “photographed by the eye”.
The macula degenerates as a result of ageing. Small yellow or white deposits called “drusen” develop under the macula in normal eyes as they age. Drusen may eventually lead to macular degeneration.
Macular degeneration occurs when the retinal pigment epithelium, the insulating layer between the retina and the layer of blood vessels behind the retina (called the choroid), stops functioning efficiently.
The macula may be damaged by blood vessels growing under the retina. The blood vessels may leak fluid or bleed (wet macular degeneration), or the retina may degenerate (dry macular degeneration).
Types of macular degeneration
Dry macular degeneration:
This is the most common form of macular degeneration. When the eye is examined, the retina appears to have degenerated in certain areas while seeming healthy in other areas. Damage to the macula is permanent, as it isn’t possible for it to grow back or heal.
At present there are no eye drops, tablets, spectacles, operations or alternative therapies proven to restore the vision that has been lost.
However, you will not go blind from this condition and will keep your peripheral vision. The disease is slowly progressive, and the rate of progress may be extremely slow. The condition eventually stabilises.
New exciting technologies like chip implants and stem cell therapy are being developed but are still in their infancy.
Wet macular degeneration:
Wet macular degeneration is much less common. It’s more rapidly progressive, but it also doesn’t cause complete blindness. Early intervention can preserve useful vision.
This type of macular degeneration occurs when abnormal blood vessels develop under the retina and leak fluid, or bleed. Untreated, the central vision is permanently damaged and a scar is formed.
Other macular diseases:
There are macular diseases and degenerations that sometimes occur in younger people. Some of these conditions are genetic, while others can be caused by infections and inflammation or underlying conditions, such as diabetes.
Causes and risk factors for macular degeneration
The causes of macular degeneration are not completely understood, but there is a genetically inherited tendency for the condition. Smoking, dietary factors and sun exposure over many years may also play a role.
Macular degeneration is most common among people of European descent over the age of 55.
Symptoms and signs of macular degeneration
Symptoms and signs of macular degeneration include:
- Blurred central vision – difficulty when reading and engaging in other activities that require good, fine eyesight
- Lost central vision – dark or empty spaces
- Distorted central vision – straight lines may appear wavy
Peripheral vision almost always remains normal.
How is macular degeneration diagnosed?
To diagnose macular degeneration, an ophthalmologist will check your eyes and note the characteristic changes in the retina.
Further (investigative) testing
Optical coherence tomography (OCT) testing is a non-invasive imaging test that uses light waves to take high-definition, cross-sectional images of your retina. With this test, the distinct layers of the retina can be seen. This test can be used to monitor your response to treatment.
Fluorescein angiography is a series of photographs taken after dye has been injected into a vein. The photographs will show the presence of abnormal fluid in the eye, changes in the condition of the retina, and exactly where these changes have occurred.
Optical coherence tomography angiography (OCTA) is a new technology that delivers the information that a fluorescein angiogram does without the need of an injection.
If you have dry macular degeneration, your ophthalmologist will ask to see you for regular check-ups. You can also monitor your own condition using an Amsler grid – a grid of horizontal and vertical lines that allows you to pick up subtle deterioration or changes in vision.
During this test, you should wear the contact lenses or glasses you usually wear for reading. If you use bifocals, you should look through the reading portion of the lens.
Holding the grid at a comfortable reading distance (usually about 30 to 35cm away), you should focus on the dot at the centre of the grid. Any wavy areas, blurred areas or blank spots observed should be marked on the grid, allowing for future monitoring of the progress of the condition.
How can macular degeneration be prevented?
People who have a family history of macular degeneration, or who experience any vision problems, should have regular eye examinations after the age of 45.
Although macular degeneration cannot be prevented, you may be able to delay the onset or slow the progression by:
- Not smoking cigarettes and avoiding cigarette smoke. Smoking is the most commonly identified factor that aggravates the condition.
- Avoiding contact with ultra-violet light (UV rays) by wearing protective eye gear that blocks out 100% of UV rays.
- Eating healthily. Proper nutrition – particularly a balanced and sufficient intake of vitamins, minerals and fresh vegetables – is believed to help prevent the condition. At the very least, it will improve your general health.
- Exercising regularly. This improves both general and eye health.
Research into the genes that cause macular degeneration continues.
How is macular degeneration treated?
Currently there’s no proven treatment for dry macular degeneration. However, in some people with the condition, supplements containing vitamins, lutein or certain trace elements such as zinc or selenium may slow the progress of the disease.
If diagnosed early, wet macular degeneration can be treated and a fairly new injection is now being used successfully. A substance called anti-VEGF (vascular endothelial cell growth factor) is injected into the vitreous humor of the eye. This injection inhibits new blood vessel growth and helps to stop leakage from the new blood vessels that causes retinal damage. The main aim of the injection is to prevent further vision loss, but sometimes it actually improves central vision.
In the case of partial blindness caused by macular degeneration, low-vision rehabilitation can help you to adjust to your condition. This type of rehabilitation helps you to make the most of your remaining vision and may include:
- Adjusting the lighting in your home.
- Visual aids and voice-activated devices.
- Seeking assistance from someone with good eyesight to perform daily tasks.
If you have incurable dry macular degeneration, your doctor or dietician may be able to recommend nutritional supplements, although the effects of these haven’t yet been clinically proven.
Outcome of treatment
The advent of anti-VEGF therapy has revolutionised treatment for individuals with wet age-related macular degeneration. The earlier the condition is diagnosed, the more successful the therapy is in slowing or halting the disease.
Low vision rehabilitation can allow people with macular degeneration who have good access to public transport and assistance from family or friends to live fairly normal lives, even if they’re partially blind.
Extensive research is being conducted into this condition, both locally and abroad. Areas of research include genetics, new lasers, surgical techniques and medicines.
When to call your doctor
Consult an ophthalmologist without delay if you experience any of the symptoms associated with macular degeneration.
You should also be regularly tested to ensure that the problem is picked up sooner rather than later. Don’t miss your annual eye test. Also always consult your eye specialist before trying any over-the-counter treatments or remedies.
Reviewed by ophthalmologist Dr Viresh Dullabh, MBBCh (Wits) FC Ophth SA (CMSA) MMED (UKZN). September 2018.