Macular degeneration is the name given to a group of retinal eye diseases that cause progressive loss of central vision. It is the leading cause of blindness and severe vision loss in New Zealand. Most commonly macular degeneration develops as the eye ages and usually affects people over the age of 50. It is referred to as Age-related Macular Degeneration (AMD). However, inherited forms of the disease can also affect young people. One in seven New Zealanders over the age of 50 has some evidence of macular degeneration. Approximately 17% of these people experience vision impairment.
It is progressive and painless. Although it can lead to legal blindness, it does not result in total or black blindness as the peripheral vision (side vision) is intact.
The macula is the central area of the retina at the back of the eye. It is responsible for detailed central vision and most color vision. It provides our reading vision, and the vision that enables us to recognize faces, drive a car and do tasks that require fine vision. The rest of the retina is called the peripheral retina and is used to see general shapes and provides ‘get-about vision’ (also called peripheral or side vision).
Macular degeneration is caused by genetic and environmental factors. Risk factors include age, family history, smoking, diet, and lifestyle factors. The incidence of macular degeneration increases with age. It can be hereditary, with a 50% chance of inheriting the genetic predisposition if there is a positive family history of the disease. Because 70% of cases of macular degeneration have a genetic link, it is important that people with the disease inform their siblings and children and encourage them to have their eyes, including the macula, checked. Smokers are 3 to 4 times more likely to develop macular degeneration and may develop the disease 5 to 10 years earlier than non-smokers. Those with a genetic predisposition who smoke have a significantly increased risk of macular degeneration.
The most common form of the disease is known as Dry Macular Degeneration. In this form, vision loss is usually very gradual. Waste products build up in the retina and areas of the central retina gradually become thin and stop working.
In some people, Dry Macular Degeneration develops into a more aggressive form of the disease called Wet Macular Degeneration. In this form, abnormal blood vessels grow under the macula and eventually leak fluid, bleed or lift up the retina. This can lead to rapid and severe vision loss. A frequent and important early symptom of Wet Macular Degeneration is distortion when straight lines appear bent or wavy. These changes should be acted on promptly and a vision examination sought as soon as possible.