Macular degeneration (AMD)
Age-related Macular Degeneration (AMD) is the leading cause of severe vision impairment in older Australians.
This disease affects one in seven people over the age of 50 and incidents increase to one in three people over the age of 75.
Macular degeneration refers to a group of degenerative diseases of the retina that cause progressive, painless loss of central vision, affecting the ability to see fine detail, drive, read and recognise faces.
Macular degeneration causes
The macula is the part of the retina in the back of the eye that ensures our central vision is clear and sharp. Age-related macular degeneration (AMD) occurs when the arteries that nourish the retina harden. Deprived of nutrients, the retinal tissues begin to weaken and die, causing vision loss. Patients may experience anything from a blurry, grey or distorted area to a blind spot in the centre of their vision.
Macular degeneration doesn’t cause total blindness because it doesn’t affect peripheral vision. Possible risk factors include genetics, age, diet, smoking and sunlight exposure. Regular eye exams help detect macular degeneration early, preventing permanent vision loss.
Macular degeneration symptoms
Symptoms of macular degeneration include:
- Gradual loss of ability to see objects clearly
- Gradual loss of colour vision
- Distorted or blurry vision
- A dark or empty area appearing in the centre of vision
Types of Macular Degeneration
There are two kinds of AMD: wet (neovascular / exudative) and dry (non-neovascular). About 10-15 per cent of people with AMD have the wet form. “Neovascular” means “new vessels.”
Wet AMD occurs when new blood vessels grow into the retina as the eye attempts to compensate for the blocked arteries. These new vessels are very fragile and often leak blood and fluid between the layers of the retina. Not only does this leakage distort vision, but when the blood dries, scar tissue forms on the retina, creating a dark spot in the vision.
Dry AMD is much more common than wet AMD. Patients with this type of macular degeneration don’t experience new vessel growth; symptoms include thinning of the retina, loss of retinal pigment and the formation of small, round particles inside the retina called drusen. Vision loss with dry AMD is slower and often less severe than with wet AMD.
Macular degeneration treatments
With any kind of AMD, you can decrease the risk of the disease worsening.
- Vitamin supplements: a large American study, the Age-Related Eye Diseases Study (AREDS), found that certain combinations of vitamins could reduce the chance of AMD getting worse by about one quarter.
- Stopping smoking: smokers are at higher risk of AMD and of Wet AMD in particular.
- Dietary changes: various foods seem to protect against the development of Wet AMD, including nuts and fish oils.
With Wet AMD, several different treatments are possible:
- Avastin and Lucentis injections: these drugs are injected into the eye and may need to be repeated several times over some months but have been shown to improve vision so long as there’s been no scarring. No other treatment appears to improve vision; other treatments can only decrease the rate at which things get worse.
- Thermal Laser Therapy (Photocoagulation): heat from a laser light is used to cauterise abnormal leaky blood vessels. This treatment also damages overlying normal retina.
- Photodynamic Therapy (PDT): a light-activated drug (Visudyne) and a special non-thermal laser selectively destroys abnormal blood vessels while preserving surrounding normal healthy tissue.