Age-related macular degeneration (ARMD) is the most common cause of irreversible vision loss in over 50 year olds. The condition does not cause total blindness, but affects the central vision area of the retina, the macula, leaving the peripheral retina unaffected. This part of the retina provides our detailed central vision, and as such macular degeneration causes gradual loss of central vision affecting activities such as reading and driving and even recognising faces. The condition is thought to be due to the accumulation of waste products within the retinal pigment epithelium.
There are two types of macular degeneration:
Dry ARMD is generally described as the better type to have. It is due to gradual damage to the photoreceptors at the macula (central part of the retina used for detailed vision such as reading). It tends to cause gradual deterioration in central (reading) vision and is generally bilateral. While there are many treatments being investigated, currently the only available treatment is antioxidant vitamin supplementation. Dry ARMD can progress causing significant destruction of the photoreceptors (geographic atrophy) and central vision loss. It can also convert to wet ARMD, and there is no way to predict if or when this will occur.
Wet ARMD is due to abnormal blood vessels growing at the macula. These vessels are fragile and can leak and bleed under the retina, and may lead to fairly rapid loss of central vision. With early detection, wet ARMD is treatable and vision can be improved and stabilised.
Age – ARMD is rare before the age of 50 but the risk increases with age. There are signs of ARMD in up to 40% of people over 75.
Family history – having a first degree relative with ARMD increases your risk.
ARMD in one eye – if ARMD is present in one eye there is an increased risk of ARMD in the other.
Smoking – is the single greatest modifiable risk factor for the development and progression of ARMD.
Diet – a poor diet low in antioxidants and high in saturated fats and processed foods increases the risk for ARMD.
Obesity and sedentary lifestyle – people who are significantly overweight or have a sedentary lifestyle are at increased risk for ARMD.
UV exposure – high UV exposure increases ARMD risk.
Dry ARMD may cause minimal visual change for some patients. The symptoms of dry ARMD tend to change slowly, while fairly sudden changes tend to be noted with wet ARMD.
Symptoms of macular degeneration can include:
Increased difficulty with reading.Requiring increased light for close work and reading.
Increased difficulty with adapting to changes in light level.
Reduction of colour brightness and intensity.
Increased difficulty recognising faces.
Distortion of letters or words when reading.
Distortion of straight lines (door frames or fence posts may appear bent or wavy).
If you are at risk of ARMD, it is important to be conscious that any change in vision (blurred vision or distorted vision) may be an early warning sign of macula problems, and that vision may deteriorate unless the problem is investigated quickly.
Regular eye examinations will screen for macular degeneration and will detect the early signs of ARMD.
Tests that may assist diagnosis and monitoring of macular degeneration include:
Visual acuity level on a letter chart.
Amsler grid test assesses distortion (such as faded, broken or wavy lines) within the central 10 degrees of vision.
Retinal examination may detect small yellow spots at the macula (drusen), in early ARMD. Haemorrhage may be seen at the macula in wet ARMD.
Optical coherence tomography (OCT) can identify areas of macular thickening or thinning and the presence of abnormal blood and fluid under the macula.
Fluorescein angiography uses a special dye and camera to look at the blood flow in the retina and choroid to detect abnormal vessels.
Fundus autofluorescence photography can be useful to show progression of dry macular degeneration.
There is no current treatment for dry ARMD, however antioxidant and nutritional supplements have been shown to reduce the risk of developing wet ARMD.
The following lifestyle and dietary changes can help prevent early dry ARMD and its progression:
Maintain a healthy weight and blood pressure.
Maintain a well-balanced diet, low in processed foods (include green leafy vegetables and fish several times a week).
Self-monitoring central vision on a weekly basis with an Amsler grid to identify new blur or distortion is very important with ARMD, as is early presentation if changes are seen.
Wet ARMD can generally be successfully treated with the use of anti-vascular endothelial growth factor (VEGF) medication injected into the eye. These drugs stop abnormal blood vessels from growing and leaking. Usually three injections at four week intervals are required to stabilise wet ARMD, and then maintenance treatment every 4 to 16 weeks after this is required to maintain the improvement in vision. The earlier treatment is commenced, the better the visual outcome will be.
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