What is age-related macular degeneration?
Macular degeneration (MD), also referred to as age-related macular degeneration (AMD), is a medical condition that typically appears in older people. It results in blurred or total vision loss in the centre of a person’s visual field. In some rare instances the disease does affect younger people, this is known as juvenile macular degeneration.
In the early stages of the disease, there are often no symptoms. An individual will usually experience gradual loss of their vision. In almost all cases, they will retain most of their peripheral vision. This may affect either one or both eyes. Although the condition will not necessarily lead to total vision loss, weak central vision can make performing daily activities such as driving and reading difficult. It will also make recognition of faces and object more challenging. It is also not uncommon for someone to experience hallucinations, although this is not a reflection of deteriorating mental health.
The condition is known to affect 6.2 million people around the globe, being fourth in the list of diseases that commonly lead to blindness behind cataracts, preterm birth and glaucoma.
What causes age-related macular degeneration?
There are several different contributing factors that can contribute to macular degeneration:
Ageing: The condition mainly affects those over the age of 50 and is the leading cause of vision loss in this age group, the chance of someone having the condition increases with age. While on 0.4% of people over 50 are reported to have the condition, over 12% of people over the age of 80 are reported to suffer from the condition.
Smoking: Somebody who smokes tobacco is almost two to three times more likely than someone who has never smoked to be at risk of macular degeneration. Toxins in cigarettes will likely have an effect on the retina, as they do in other parts of the body. Previous studies have shown a very strong link between smoking and macular degeneration making it one of the most modifiable factors in preventing its development.
Genetics: Reoccurrence is higher in those who have a sibling with the condition than those in the rest of the general population. Genes are likely to play some part, however genetics cannot completely predict the progression of the disease.
High blood pressure: a 2013 study (ALIENOR) showed that elevated pulse pressure ((PP) systolic BP minus diastolic BP) was significantly associated with an increased risk of late AMD, however, the use of antihypertensive medication and hypertension it’s self was not.
Other (debated) causes include: atherosclerosis, high cholesterol, obesity (more commonly among men), a high intake of saturated and trans fats and exposure to sunlight.
What are the symptoms of age-related macular disease?
Because the symptoms of macular degeneration are similar to other eye conditions, most people will not be aware exactly what the problem is initially. If in doubt, it’s advised you see an optician to be properly diagnosed. A diagnosis can be done by an eye exam.
Symptoms may include any of the following:
- Individuals may experience that they take longer to recover visual clarity after exposure to bright light
- Visual acuity will decrease by a few levels - 2/20 to 20/80 is usually a clear indicator
- Difficulty distinguishing between colours, distinguishing dark shades from other dark shades and light shades from other light shades
- A loss in contrast sensitivity
- Overall vision will be distorted due to metamorphopsia where an individual will see a grid of straight lines that may turn wavy, or have blank areas.
The severity of the condition is divided into different types/stages: early, intermediate, and late. The late type is additionally divided into "dry" and "wet" forms with the dry form making up 90% of cases.
In early AMD, there will be a medium sized drusen (build-up of extracellular proteins and lipids) present. Early AMD is usually asymptomatic, meaning symptoms won’t be noticeable
In intermediate AMD you will find a larger drusen and/or retinal pigment abnormalities. Like early AMD, it is usually asymptomatic.
In late AMD, there will be enough retinal damage that an individual will have noticeable vision loss as well as drusen.
Dry AMD is the more common of the two strands of late AMD, developing much slower (sometimes taking years) and having a more gradual effect on central vision. It develops very slowly and causes a gradual change in your central vision. However, it doesn’t affect your peripheral vision, so does not lead to total blindness, but can cause a blind spot in your central vision.
When the cells of the macula stop functioning as they should, your blood cells create new blood vessels to fix the problem. This is when Wet ADM develops. The blood vessels grow in the wrong place and cause swelling and bleeding underneath the macula. This damages the macula and causes scarring.
How is macular degeneration treated?
At present, there no complete cure for age-related macular degeneration (AMD), although there are treatments that can slow the process and help those already affected live a good quality of life. AMD has to be approached differently depending on they type.
A good healthy diet will help improve your quality of life overall, but there is some suggestion that certain foods will help prevent AMD, particularly Dry ADM.
Vitamins A (beta-carotene), C and E – as well as substances called lutein and zeaxanthin are of great importance when keeping your eyes safe from AMD. Food high in these vitamins include kiwis, leafy greens, organs, tomatoes, carrots, mangos, peas and sweetcorn.
There are also visual aids that can keep your vision sharp and eyes safe from dry eye, such as large printed books, magnifying glasses, bright reading lights and smart screen reading software.
Wet AMD is treated by medications called anti-vascular endothelial growth factor drugs. These stop blood vessel growth which leads to sight damage. The medication is injected into the vitreous: a gel-like substance inside the eye. The injection should be given in an operating theatre or ‘clean room’ to avoid potential infection.
Prior to the injection, you should be given an anaesthetic drug to ease pain and antibiotic drop to prevent infection. You may get swirls or blurriness in your vision after the injection for a short time afterwards. Injections are usually given in a course for one or a few months to begin with.
Anti-VEGF mediations have a high success rate with over 40% of people seeing an improvement in their vision. It is advised however, that you start treatment as early as possible as this treatment cannot repair underlying damage.
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