Health

Saturday 26 July 2014

Ask the doctor: Will macular degeneration make me go blind?

I have noticed I can't see things as clearly as usual recently so I paid a visit to my optician. I was sent from there to see an eye doctor who tells me that I have macular degeneration. I had never heard of this before and am quite worried. Does this mean that I am going blind?

A Our eyes are literally our window to the world and it is important that we care for them throughout our lives. The eye is quite a complex organ that converts light images into brain signals and makes sense of the world around us.

Light passes through the front of the eye and hits the retina at the back where information is then passed on to the optic nerve on the way to the brain. The macula is the most light sensitive part of the retina and is responsible for clear central vision. Macular degeneration (MD) occurs when the cells of the macula become damaged.

It is the most common cause of vision loss in those over 50 although it occurs most commonly in those over 60. Smoking also increases the risk of this condition. Caucasians are affected more than other races. More recently evidence suggests that a diet low in fruits and vegetables also plays a role. High blood pressure and exposure of the eyes to direct sunlight have also been implicated. However, the exact cause of macular degeneration is unknown. Macular degeneration won't cause complete blindness but causes loss of central vision. This is necessary for reading, driving and recognising faces, so this condition can be very debilitating.

There are two main types of MD. Dry MD occurs in about nine out of 10 cases. In dry MD the cells of the retina become thin and degenerate. This occurs slowly over time and initially symptoms may not be obvious. As the condition progresses a person may notice difficulty adapting to or reading and working in low light conditions. Printed words may appear blurred. Faces may become more difficult to recognise and colours may appear less intense or bright. Ultimately, vision becomes hazy and a blurred or blind spot occurs in the centre of vision.

Wet MD accounts for about one out of 10 cases. In wet MD abnormal blood vessels grow beneath the retina theses may swell and leak causing damage to the macula. Wet MD can occur rapidly, causing severe damage. It is possible to have both types of MD. Macular degeneration can only be fully diagnosed with a full ophthalmology exam which is why your optician suggested an eye specialist referral. There is no cure for macular degeneration but treatment may prevent it from advancing. MD is described as early, intermediate or late. There is no specific treatment for early MD. Lifestyle management such as stopping smoking, exercising well and eating a broad, varied diet including green leafy vegetables is advised. The eyes should be checked yearly at this stage. Research suggests a specific combination of vitamins and antioxidants can help slow the progression of MD.

A specific vitamin combination is recommended by the National Eye Institute of America. This includes 500mg Vitamin C, 400 IU Vitamin E, 15 milligrams beta carotene, 80 milligrams zinc oxide and 2mg copper (cupric oxide). A second review of nutritional supplements advised decreasing the zinc to 25mg as a high zinc intake has been related to kidney and bladder problems.

The beta carotene was also replaced with 10mg lutein and 2mg zeaxanthin as beta carotene has been linked to an increased risk of lung cancer in current and former smokers so the new combination was considered safer. There are a number of special vitamin supplements sold which are designed specifically for eye care.

In advanced cases of wet MD the injection of specific drugs directly into the eye can be helpful. These drugs block the formation of new abnormal blood vessels. These drugs improve vision in about one in three people but will maintain vision and prevent the condition getting worse in most people treated. Another treatment involves injecting a substance into a vein in the arm. This travels to the vessels in the eye and when laser light is applied it can help destroy the abnormal vessels. This is photodynamic therapy.

Other laser therapy is also sometimes used to target the abnormal blood vessels. Some people with advanced symptoms suffer from visual hallucinations.

This is called Charles Bonnet syndrome and is felt to be similar to phantom pain felt by those who have had amputations. The eye creates vision in the area where there is none. It's important to know that if these occur it is not a sign of a mental health disorder and in most people these go away within about a year to eighteen months.

 

drnina@independent.ie

Dr Nina Byrnes is now on Twitter @ DrNinaByrnes

Irish Independent

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