The aging eye

Sunday, October 26, 2008

AMD is not painful and does not lead to complete loss of vision. So one can learn to cope with the loss of the central vision.

Blind spot: Reading writing and recognising people may be difficult.

The eye is shaped like a ball. The pupil, close to the front, allows light to enter the eye. Just behind the pupil is the lens, which focuses the light on the retina at the back of the eye. The retina converts the light into images, and sends them to the brain. The macula is a small area at the centre of the retina that is responsible for what we see straight in front of us, allowing us to see fine detail for activities like reading and writing, and our ability to see colour.

Sometimes the delicate cells of the macula become damaged and stop working due to many different conditions. If it occurs late in life, it is called “age-related macular degeneration” or AMD.

Broadly speaking, there are two types of AMD, usually referred to as “wet” and “dry”. This is not a description of what the eye feels like but what the ophthalmologist can see when looking at the macula. “Dry” AMD, the most common form, develops very slowly causing gradual loss of central vision. There is no medical treatment for this type. However, aids such as magnifiers can be helpful with reading and other small detailed tasks.

“Wet” AMD results in new blood vessels growing behind the retina causing bleeding and scarring, which can lead to sight loss. “Wet” AMD can develop quickly and sometimes responds to treatment in the early stages.

Both kinds usually involve both eyes, although one may be affected long before the other. This may make the condition difficult to notice at first because the sight in the “good” eye compensates for the loss of sight in the affected eye.

The good news is that AMD is not painful, and almost never leads to total blindness because only the central vision is affected. This means that almost everyone with AMD will have enough side (or peripheral) vision to get around and keep his or her independence.

Blurred vision

In the early stages, central vision may be blurred or distorte. This may happen quickly or develop over several months. The patient may be very sensitive to light or actually see lights, shapes and colours that are not there. This may cause occasional discomfort.

Because AMD affects the centre of the retina, people with the advanced condition will often notice a blank patch or dark spot in the centre of their sight. This makes reading, writing and recognising small objects or faces very difficult.

If you suspect that you may have AMD see an eye specialist. First, there will be an assessment of vision in both eyes. Then the eye will be dilated so that the eye specialist can look into your eye. If you are diagnosed with AMD, you will receive an Amsler grid, which helps you to keep track of any minor change in your vision on a daily basis, a sign of wet AMD. This quick test works best for people who still have good central vision.

In some cases fluorescein angiogram will also be needed. This involves taking a rapid series of photographs of your retina with bright flashes of blue light. These photographs give an accurate map of the changes occurring in the macula and help your eye specialist to decide on the best treatment.

If you have “wet” AMD affecting the middle of the macula, in some cases, photodynamic therapy (PDT) or the Visudyne therapy is possible. This involves infusing a light sensitive drug through your bloodstream to identify the new blood vessels growing in the wrong place behind the retina. A “cold laser” is then shone into the eye to activate the drug thus destroying the new blood vessels preventing them from causing too much damage. This can help stop the “wet” AMD progressing to its worst stages though more than one treatment may be needed.

The second option is Laser Photocoagulation. While this process cannot restore vision, it seals leaky blood vessels and inhibits their growth in selected cases. This prevents further vision deterioration in a small percentage of patients. Laser provides a concentrated beam of high energy light, resulting in scar formation in the area treated. This creates a permanent blind spot in the field of vision. However this loss of vision is usually less severe than the eventual vision loss if the disease is left untreated.

New treatment

Newer treatments for “wet” macular degeneration are being developed. Anti VEGF (anti-Vascular Endothelial Growth Factor) therapies are the next group of treatments. They involve an injection into the eye that stops the development of the new leaky blood vessels. The injections have to be repeated on a monthly or bi-monthly basis.

Like PDT it is limited to people whose “wet AMD” affects the middle of the macula and its main aim is to stop it from getting worse. However, in some cases, it has been shown to restore some of the vision already lost and it can help with a wider range of people than PDT.

At the moment there isn’t any medical treatment for “dry” AMD. Some research suggests that vitamin supplements can help slow the progression. Studies have shown that a combination of high-dose beta-carotene, vitamin C, vitamin E, and zinc can reduce the risk of developing advanced AMD by about 25 per cent in those patients who have earlier but significant forms of the disease. This is the only proven intervention to decrease the risk of advanced AMD at this time. They do not restore sight, but may have a preventative role.

A natural reaction to being diagnosed with AMD is to feel upset or worried about the future. Adjusting to any major change in life can feel difficult, so you may need some support especially at first. If you would like to talk things over with someone outside your circle of friends or family your family doctor may be able to help you find a counsellor.

The Macular Disease Society ( has local groups and a telephone counselling service. Talking about and sharing experiences can be a good way of learning to cope with feelings and problems that other people with the same condition may also have come across before.

Don’t be discouraged. You can be helped make the best use of your remaining sight. This means learning to use your side (or peripheral) vision. Low vision services can help find the best magnifiers for you and give advice and training on the many ways, often quite simple, in which you can make the most of your remaining sight. Ask your eye specialist, optometrist (optician) or GP about a low vision service near by.

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Risk factors

At the moment the exact cause for AMD is not known. However risk factors have been identified.

Age: AMD is an age related condition so growing older makes the condition more likely.

Genetics: There appear to be a number of genes, which can be passed through families and may have an impact on whether someone develops AMD or not.

Smoking: Smoking has been linked to the development of AMD. Studies have also been shown that stopping smoking can reduce the risk of developing AMD.

Sunlight: Some research suggests that lifetime exposure to sunlight may affect the retina. Wear sunglasses to protect the eyes.

Nutrition: Research suggests some vitamins and minerals can help protect against AMD.

Cardiovascular status: High cholesterol, obesity, Hypertension

High fat intake: This also causes increased risk of AMD. Eat more cold-water fish, (at least twice weekly and any type of nuts.

Oxidative stress: It has been proposed that age related accumulation of low molecular weight, phototoxic, pro-oxidant melanin oligomers in the retinal pigment epithelium may be partly responsible for lipofuscin formation - a classic sign associated with macular degeneration.


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