Macular degeneration (mate karu-tiro-pū) is the most common cause of vision loss in adults aged 50 or over.
Macular degeneration affects central vision rather than side vision. Vision loss may be a gradual process (dry AMD) or a sudden one due to a leakage of blood vessels (wet AMD). Treatment is available to help prevent further loss of vision in wet AMD. For dry AMD, measures to help prevent visual loss may include nutritional supplements. Lifestyle measures such as not smoking, eating a nutritious diet and exercising regularly are also important.
The macula is a small area at the centre of the retina - the light-sensitive inner lining of your eye. The macula contains the highest concentration of light-sensitive cells. These cells are responsible for detailed central and colour vision. Central vision is needed for seeing straight ahead, and is used in tasks such as sewing, reading and driving. In AMD, central vision becomes distorted.
Wet & dry forms of AMD
There are two types of macular degeneration: ‘dry’ and ‘wet’ AMD.
- Dry AMD is the most common type (85-90% of all cases). It is a slowly progressing disease involving age-related ‘wear and tear’ to the macula. Patients with dry AMD have gradually worsening or distorted central vision.
- Wet AMD accounts for the remaining 10-15% of cases. It is caused by the growth of abnormal blood vessels underneath the macula. The abnormal blood vessels leak blood and fluid into the retina, causing rapid loss of central vision. Eventually, scarring forms in the macular region, leading to permanent loss of central vision. The majority of patients who develop severe loss of vision from AMD have this form of macular degeneration (over 80%).
AMD damages central vision. This makes tasks such as reading, telling the time, recognising faces and driving extremely difficult or impossible to perform. AMD is the leading cause of legal blindness in New Zealand. However, patients with AMD never develop total blindness, because peripheral (side) vision is kept.
- One in 7 people over the age of 60 years is affected by AMD.
- AMD may develop slowly (dry AMD) or rapidly (wet AMD).
- AMD causes loss of central vision which is needed for tasks such as reading, sewing and driving.
- Symptoms include blurring and distortion of central vision.
- It is the leading cause of blindness in NZ.
- See a doctor or eye specialist without delay if you develop visual loss or visual distortion.
The causes of AMD are unclear; however, several risk factors for AMD have been identified:
- Increasing age is the leading risk factor for AMD. AMD affects approximately 1-2% of those less than 60 years, jumping to 15-20% for those over 80 years.
- Family history is also an important risk factor for AMD. You are much more likely to be affected if your mother, father or other closely related family member had/has AMD.
- Those of Caucasian ethnicity are more commonly affected than other ethnicities.
- Females are more likely to be affected than males.
- Smoking - studies suggest that smokers have at least three times the risk of developing AMD compared to non-smokers. They also develop AMD 10 years earlier on average. Former smokers have a lower risk compared to current smokers.
- Poor nutrition - a diet high in vegetable, monounsaturated and polyunsaturated fats, high-fat dairy food, processed food, and high in high sugar foods all increase the risk of AMD.
- Other risk factors include high blood pressure, heart disease, high cholesterol, obesity and lack of exercise.
Symptoms of dry AMD tend to develop slowly. You may not notice any symptoms in the early stages. It can take 5-10 years for symptoms to become severe. With wet AMD, symptoms become severe quickly.
Common symptoms of AMD include:
- blurring of central vision which makes close work such as reading difficult
- colours appear duller
- a blind or dark spot in the centre of your vision which gets bigger over time
- distorted central vision which makes straight lines look wavy
- difficulty recognising faces.
Eventually, if left untreated, you may experience complete loss of central vision.
If you develop visual loss or visual distortion, see your doctor or eye specialist without delay. It could be a sign of AMD or another eye disorder. The sooner you seek help, the better.
Amsler grid to detect vision problems - Macular degeneration NZ
Treatment for wet AMD
In the past there were limited treatment options available for wet AMD. However, in recent years, there have been major advances which now means many patients are able to keep their vision.
- Treatment with medication called anti-VEGF agents (like Avastin or Lucentis) have been shown to help wet AMD and improve vision.
- These medications are given as a small injection into the eye and may need to be repeated.
Prevention vision loss in dry AMD
There is currently no treatment available to restore vision lost as a result of dry AMD. Therefore, preventing visual loss is the most important aim of treatment in the management of patients with dry AMD. One preventative measure available is nutritional supplementation (see below). This may help to slow the progression of AMD and prevent vision loss in some patients.
Other factors that may help slow the progression of AMD include:
- quit smoking
- improving diet by including green leafy vegetables, fruits, berries, fish and avoiding high-fat foods
- exercising regularly
- treating conditions like high blood pressure and cholesterol, heart disease and obesity
- minimising ultraviolet light exposure by using sunglasses.
Regular eye checks
It is important to have your eyes checked regularly by an optometrist or ophthalmologist. This is especially important if you are over 60 years of age, as the risk of many eye disorders increases as we age.
If you have no risk factors, an eye examination is recommended:
- every 5 years if you are under 60 years of age
- every 3 years if you are over 60 years of age.
If you have any risk factors your eye specialist may recommend frequent examinations.
Several studies have identified nutritional factors that may help protect against AMD. These include:
- omega-3 fatty acids (in fish)
- the carotenoids lutein and zeaxanthin (in green leafy vegetables, fruits and some berries)
- antioxidants (mainly vitamins C and E, and zinc).
Talk to your optometrist or ophthalmologist (eye specialists) for more information, or contact the following organisations for support and information:
Patients who have lost significant vision may benefit from low vision aids and should be referred to a low vision service. The Royal New Zealand Foundation of the Blind (RNZFB) is the main provider of vision-related services to blind and partially-sighted individuals in New Zealand.
Dry macular degeneration Mayo Clinic - Mayo Foundation for Medical Education and Research, 2012
Wet macular degeneration Mayo Clinic - Mayo Foundation for Medical Education and Research, 2012
Macular degeneration Eye Institute Auckland, NZ