Age Related Macular Degeneration (ARMD or AMD)
Age related macular degeneration (ARMD or AMD) is the commonest cause of visual impairment in the UK and accounts for almost 50% of reduced sight in the developed world. It occurs when the macular (the part of the retina at the back of the eye responsible for central vision) starts to malfunction or gets damaged.
The cause of AMD is not fully understood but extensive research suggests that the following factors play a role in the development of the condition:
AMD is generally a disease which affects people over the age of 65yrs. It is very unusual in younger individuals, although this group can get other rarer macular conditions, which are generally termed "macular dystrophies".
Females are affected more than men, approximately twice as often in those over 75 yrs old.
AMD is generally not inherited but some genes have been identified as being involved with AMD and may be a significant factor in some families. AMD is commonest in people from Caucasian (white) racial backgrounds.
- Smoking and Hypertension
Smoking definitely increases the risk of developing AMD and there is weaker evidence suggesting that poorly treated hypertension (high blood pressure) may also be important.
Ultra-violet light (UVA and UVB) possibly increases the likely hood of macular damage in some people. Wearing sunglasses with a UV light filter may be beneficial.
Research suggests that various minerals and vitamins are important for macular function, in particular zinc, copper and vitamins A,C,E. These are generally present naturally in fresh fruit and green leafy vegetables. Higher concentrations are often recommended in daily tablets which are often not available on prescription but can be easily purchased. It is worth discussing these supplements with your doctor as some may be contraindicated eg beta-carotene appears to increase the risk of lung cancer in smokers and should therefore be avoided.
Types of AMD
There are two main types of AMD as follows:
- 1. "Dry" AMD
- This is by far the commonest type, accounting for 90% of all cases of AMD. It can be considered as "macular ageing" whereby some of the retinal layers and light capturing cells (photoreceptors) become less effective. Dry AMD tends to be a slow process, with visual function usually deteriorating gradually over many years. Initially people may have difficulty with fine detailed vision eg reading small print, even when wearing appropriate spectacles. In more significant cases the central vision becomes more blurred, or even patchy, making near and distant tasks difficult. Advanced dry AMD often results in a dense smudge, or even a dark patch, in the central vision. Although the peripheral side vision remains unaffected the profound loss of central vision can mean that it is extremely difficult or impossible to recognise faces, watch TV etc.
- There is considerable research into dry AMD with several potential new treatments being evaluated. However, currently there are no specific methods of reversing the condition. There is evidence that life-style changes can help slow disease progression. These include stopping smoking, controlling hypertension, wearing sunglasses and having a healthy diet (or taking mineral and vitamin supplements). If both eyes are affected a low vision aid assessment is usually helpful to discuss lighting and ensure that the best possible optical devices eg stronger spectacles, magnifiers or telescopes are available. People with more advanced AMD often benefit from being registered with reduced vision - "Certificate of Visual Impairment (CVI)".
- 2. "Wet" AMD
- This type of AMD accounts for the other 10% of cases. It results from small fragile blood vessels (neovascularisation) growing into the retina from the layer beneath (choroid). These vessels are prone to bleed which results in scarring in the macular area. Unlike dry AMD which affects central vision slowly, wet AMD often results in a more rapid loss of vision. The affected individual may notice central blurring or distorted vision (straight lines looking wavy). Typically the vision deteriorates over a matter of weeks and months (rarely hours or days).
- It is not always easy to determine whether someone has dry or wet AMD, even after a full ophthalmological assessment. However an accurate diagnosis can be made using additional investigations:
- Fluorescein angiography is a technique used for examining the retinal circulation and for detecting abnormal blood vessels in the macular area. A dye is injected intravenously into the arm, travels to the back of the eye and its path can be photographed using a special camera with a filter.
- Optical coherence tomography (OCT) is a device which uses light signals (like an "optical ultrasound") to build up a 3-dimensional picture of the macular area. No injections are required and the pictures are obtained within a matter of minutes. OCT is extremely useful at detecting leaking blood vessels in the macular area, and therefore distinguishing between the different types of AMD.
Treatment of "wet" AMD
Anti-VEGF medication is now the first line treatment for wet AMD in the vast majority of cases. VEGF stands for "vascular endothelial growth factor", one of the chemicals responsible for the eye producing weak fragile blood vessels in the macular. Anti-VEGF treatment works by blocking these chemicals and therefore preventing the signals which stimulate vascular growth. The anti-VEGF medication is injected into the eye (intra-vitreal), under local anaesthetic, using a very fine needle. This is most often done in a "clean" room in the out-patient's department.
The National Institute for Health and Clinical Excellence (NICE) appraised anti-VEGF therapies and in August 2008 approved the use of Ranibizumab (brand name is Lucentis). There are specific inclusion criteria for being eligible for this treatment under the National Health Service (NHS). Those patients who, having been fully investigated, meet the requirements have the drug injected into the affected eye once a month for three months. The effect is then evaluated in order to establish the response and formulate a management plan, often regular surveillance and further injections are required.
Studies suggest that ranibizumab can help slow the deterioration in central vision in 90% of cases and may even improve vision in 30%. Unfortunately approximately 10% of people with wet AMD do not respond to anti-VEGF treatment. Like some people with dry AMD in both eyes it is often helpful to undergo a low vision aid assessment to ensure the most appropriate optical aids are available. Where appropriate registration using the "Certificate of Visual Impairment (CVI)" can also be extremely useful.
Additional information, especially on national and local societies and support groups, is available using the following links: