Age-related macular degeneration (AMD) is the most common macular disease in Australia. It causes progressive loss of central vision, leaving the peripheral vision intact.
AMD is related to aging but is not normal and does not affect everyone. About 1 in 7 Australians over the age of 50 have signs of AMD.
The macula is the name given to the centre of the retina, which is the specialized nerve fibre layer at the back of the eye that detects light and color, and sends electrical signals to the brain to process visual images. The macula is responsible for our clear central vision, particularly for fine detail. We use our macula to perform important tasks such as reading, recognizing faces, seeing street signs whilst driving, and recognizing color and contrast.
AMD is a disease in which the macula degenerates with age in a specific way. It is related to aging but is not a normal part of the aging process. AMD is a chronic and painless condition that causes progressive loss of the central vision but leaves the peripheral vision intact. It affects the ability to perform activities that require clear central vision, but never results in complete blindness.
There are 2 types of AMD:
1. Dry AMD:
This is the most common type of AMD, accounting for about 90% of cases. In this type, visual loss is usually very slow and gradual. Most patients with the dry type will not lose significant parts of their central vision in their lifetime. Gradual central visual blur, with increasing difficulty with tasks such as reading, occurs over many years.
In the early stages of dry AMD, protein deposits known as drusen accumulate under the retina, and are seen as yellow spots at the macula. This is seen when the eye is examined under the microscope and confirmed with advanced diagnostic equipment, most commonly the OCT scan.
Over time, the tissue at the macula thins and atrophies, leading to loss of macula function and vision. This is known as geographic atrophy.
There is no cure for dry AMD, but certain dietary measures and vitamin supplements may help to slow its progression in some patients.
A small proportion of patients with dry AMD convert suddenly to the wet type of AMD. There are certain risk factors that can identify which patients are more prone to this, but it cannot always be predicted.
2. Wet AMD:
This type accounts for only 10% of cases of AMD but is much more aggressive and severe than the dry type. It can cause more rapid and severe central visual loss than the dry type. Patients will experience rapid blurring of their central vision, as well as missing spots (scotomas) and distortion (metamorphopsia) of their central vision.
In wet AMD, abnormal blood vessels begin to grow under the retina at the macula. These abnormal blood vessels are called choroidal neovascular membranes (CNVM), as they originate from the choroidal layer of the eye, which provides the blood supply to the retina. The CNVM bleed and leak fluid into the macula, leading to the visual symptoms described above. In the advanced stages of wet AMD, a dense scar forms at the macula, leading to a permanent patch of lost central vision in the eye.
Treatments are now available which can halt, or at least slow down, the rapid vision loss of wet AMD. The earlier in the disease this treatment is started, the better the visual prognosis. Dr Then will always educate patients with dry AMD on how to monitor for early symptoms of wet MD, usually with the use of an Amsler Grid (below).
1. Dry AMD
- Blurry central vision for near and/or far. Difficulty focusing on fine details
- Blank or dark spots in central vision
- Difficulty adapting to light change, especially from light to dark conditions
- Colors appear less vivid
2. Wet AMD
- Sudden loss of central vision
- Dark and missing spots in central vision
- Distortion of central vision (eg straight lines appear wavy or bent)
Age and genetic changes are the most common risk factors for both types of AMD. It is rare to develop AMD before the age of 50yo, but up to a 30% risk if you are aged over 75yo. If you have a family history of AMD, particularly in your parents or siblings, the risk may be as high as 50%.
Other known risk factors include smoking, excess UV (sunlight) exposure, and high blood pressure or cholesterol. In patients who have dry AMD, there is a higher risk of conversion to wet AMD if there are a high number of large soft drusen at the macula. In patients with wet AMD in one eye, there is a higher risk than normal of developing wet ADM in the other eye also.
AMD is usually apparent on clinical examination of the macula by an ophthalmologist. However, more detailed imaging is required to confirm the diagnosis. These days, most wet MD can be safely and accurately be diagnosed with OCT scanning of the macula.
Other investigations may also be required to confirm the presence and type of wet MD present. An angiogram is a test that looks specifically at the circulation within the retina, and can be performed non-invasively (OCT-angiogram) or invasively with a fluorescein dye (Fluorescein-angiogram). Dr Then will discuss with each patient whether they require an additional angiogram test to optimize their treatment.
There is no cure for the dry or wet types of AMD. However, there are certain measures that can be taken to slow down the progression of the disease.
1. Nutritional/dietary measures
A beneficial diet for patients with AMD is:
- High in dark green leafy vegetables, as well as other colorful fruits and vegetables high in lutein and zeaxanthin
- High in oily fish (rich in omega-3 fatty acids)
- Low in saturated fats
We have detailed information leaflets in our clinic about the best nutrition for AMD. Please ask our friendly staff for a copy of these.
2. Vitamin supplements
Two large clinical studies, the Age-related Eye Disease Study 1 and 2 (AREDS-1 and AREDS-2) have shown certain vitamins are of benefit in lowering the risk of AMD progressing to more advanced stages. These benefits have been most pronounced in patients with advanced dry AMD, and wet AMD. The benefits were minimal in patients with mild AMD or no AMD. There was also no benefit shown from taking these supplements if you have a family history of AMD but no AMD yourself.
The AREDS-1 and AREDS-2 trials recommended the daily intake of vitamins as follows:
- Vitamin C 500mg
- Vitamin E 400IU
- Lutein 10mg
- Zexanthin 2mg
- Zinc oxide 80mg
- Cupric oxide 2mg
Many companies now sell multi-vitamin tablets with these nutrients, but it is important to check that the nutrient doses meet the requirements recommended by the AREDS trials. It is also important to check with your GP to ensure that these nutritional supplements are safe to take in conjunction with any other medications you may be on.
Commonly found supplements that meet the AREDS guidelines are:
- Macu-Vision Plus
- MD EYES
3. Intravitreal injection therapy for wet AMD
Anti-VEGF drugs target a particular growth factor (Vascular Endothelial Growth Factor or VEGF) that causes abnormal blood vessels to grow under the retina in the wet type of AMD. By blocking VEGF, anti-VEGF drugs will reduce the proliferation and subsequent bleeding and fluid leakage of these abnormal blood vessels under the retina, which causes the rapid and severe vision loss in wet AMD. These drugs have been revolutionary in the management of wet MD, helping to slow or halt severe vision loss, and in some cases, improve vision.
Anti-VEGF drugs include Lucentis (Ranibizumab), Eylea (Aflibercept) and Avastin (Bevacizumab). These drugs are administered with direct injection into the vitreous cavity at the back of the eye, a procedure usually performed quickly and safely under local anaesthetic in our dedicated procedure room located in our clinic.
A course of 3 injections given one month apart are required to initiate treatment and this is then followed by regular injections at 1-3 monthly intervals, depending on the patient’s response over time. Duration of treatment will vary significantly between patients, but on average are for a minimum of 18mths to 2 years. Many patients will require long-term injection treatment to maintain their best vision.
4. Laser photocoagulation and photodynamic therapy for wet ARMD
Both these therapies aim to seal the abnormal leaky blood vessels that form in wet AMD. Neither treatment is as effective as anti-VEGF therapy at stabilizing or improving vision in wet AMD, and both treatments often require repetition over time to maintain effect. They may have a place in treating rare variants of wet AMD or wet AMD which is not eligible for anti-VEGF therapy.
It is important to remember that AMD will not result in complete blindness. Even the most advanced cases of AMD still retain useful peripheral vision. Many patients live full and productive lives with either form of AMD. The long-term management of AMD aims to:
- Detect dry AMD early so that measures can be put in place to slow down disease progression, with dietary and nutritional supplements, and cessation of risks like smoking and UV exposure.
- Detect wet AMD early, as visual prognosis is better the earlier anti-VEGF treatment is started. Regular self-monitoring for symptoms of wet AMD by patients, and regular eye checks with your eye specialist will help detect and diagnose wet ARMD early.