What is the macula?
The macula is the central region 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 small print, recognizing faces, seeing street signs whilst driving, and recognizing color and contrast.
What is Age-Related Macular Degeneration (ARMD)?
ARMD is a disease in which the macula degenerates with age in a specific way. There is a progressive loss of the nerve fibres at the macula, which leads to loss of central vision. ARMD never affects the peripheral vision, so even when advanced, patients never go completely blind with ARMD.
Types of ARMD
There are 2 types of ARMD:
This is the most common type of ARMD, accounting for about 90% of cases of ARMD. 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 ARMD, protein deposits known as drusen accumulate under the retina, and are seen as yellow spots at the macula. This is confirmed on OCT scans. Over time, the tissue at the macula thins and atrophies, leading to loss of macula function and vision.
A small proportion of patients with dry ARMD convert suddenly to the wet type of ARMD. There are certain risk factors that can identify which patients are more prone to this, but it cannot always be predicted. All patients with dry ARMD are therefore educated by their ophthalmologist to regularly monitor their vision with an Amsler grid for early changes of wet ARMD, as the earlier this is detected and treated, the better the prognosis.
There is no cure for dry ARMD, but certain dietary measures and vitamin supplements may help to slow its progression in some patients.
This type accounts for only 10% of cases of ARMD, 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 ARMD, abnormal blood vessels begin to grow under the retina at the macula. These abnormal blood vessels are called choroidalneovascular membranes (CNVM), as they originate from the choroidal layer of the eye, which provides the blood supply to the retina. The CNVM bleeds and leaks fluid into the nerve fibres of the macula, leading to the visual symptoms described above. In the advanced stages of wet ARMD, 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 ARMD. The earlier in the disease this treatment is started, the better the visual prognosis.
What are the symptoms of ARMD?
• 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
• Sudden loss of central vision
• Dark and missing spots in central vision
• Distortion of central vision (eg straight lines appear wavy or bent)
Click here to learn how to use an Amsler grid to detect the early symptoms of wet ARMD.
What are the risk factors for ARMD?
Age and genetic changes are the most common risk factors for both types of ARMD. It is rare to develop ARMD before the age of 50yo, but up to a 30% risk if you are aged over 75yo. If you have a family history of ARMD, particularly in a first degree relative, the risk may be as high as 50%.
Other known risk factors include:
- Excess UV (sunlight) exposure
- High blood pressure or cholesterol
In patients who have dry ARMD, there is a higher risk of conversion to wet ARMD if there are a high number of large soft drusen at the macula. In patients with wet ARMD in one eye, there is a higher risk than normal of developing wet ARDM in the other eye also.
How is ARMD diagnosed?
ARMD is usually apparent on clinical examination of the macula by an ophthalmologist. OCT scanning of the macula also helps to clearly define the extent of the ARMD, and differentiate between the dry and wet types of ARMD.
If wet ARMD is diagnosed, a fluorescein angiogram is required to confirm the presence and location of the abnormal blood vessels. The fluorescein angiogram will also help determine if the wet ARMD is suitable and eligible for treatment with intravitreal injection therapy.
What is the treatment for ARMD
There is no cure for the dry or wet types of ARMD. However, there are certain measures that can be taken to slow down the progression of the disease in some patients.
A beneficial diet for patients with ARMD 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 onega-3 fatty acids)
- Low in saturated fats
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 ARMD progressing to more advanced stages. These benefits have been most pronounced in patients with advanced dry ARMD, and wet ARMD. The benefits were minimal in patients with mild ARMD or no ARMD. There was also no benefit shown from taking these supplements if you have a family history of ARMD but no ARMD 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.
3.Intravitreal injection therapy for wet ARMD
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 ARMD. 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 ARMD. These drugs have been revolutionary in the management of wet ARMD, 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 simply in the ophthalmologist’s clinic under local anaesthetic.
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.
4.Laser photocoagulation and photodynamic therapy for wet ARMD
Both these therapies aim to seal the abnormal leaky blood vessels that form in wet ARMD. Neither treatment is as effective as anti-VEGF therapy at stabilizing or improving vision in wet ARMD, and both treatments often require repetition over time to maintain effect. They may have a place in treating specific variants of wet ARMD (eg idiopathic polypoidalchoroidalvasculopathy) or wet ARMD not eligible for anti-VEGF therapy (egextrafoveal wet ARMD)
What long-term monitoring of ARMD is required?
It is important to remember that ARMD will not result in complete blindness, as in even the most advanced cases, peripheral vision will still be retained. Many patients live full and productive lives with either form of ARMD. The long-term management of ARMD aims to:
- Detect dry ARMD 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 ARMD early, as visual prognosis is better the earlier anti-VEGF treatment is started. Regular self-monitoring for symptoms of wet ARMD by patients, and regular eye checks with the ophthalmologist, will help detect and diagnose wet ARMD early.
Click here to learn how to use your Amsler Grid.
Support and further information
There are many resources that can help educate, support and assist patients living with ARMD. These include: