Published in the Waikato times feature September 2010

AS the population ages; the incidence of age-related disease increases.  Loss of vision is one condition we often surrender to as a natural part of ageing, but it need not progress to severe impairment if we heed early signs.

Macular degeneration is the leading cause of severe vision loss. One in seven people over the age of 50 is affected and the incidence increases with age, until half of those over 80 have a form of the disease.

Macular degeneration means atrophy of the macula at the centre of the retina, the light sensitive tissue at the back of the eye. The macula is the part of the eye used for reading, recognising faces, driving and other detailed visual tasks.  With macular degeneration, central vision is weakened by obscurity, dark areas or distortions while, peripheral vision remains intact.

Hamilton Eye Clinic ophthalmologist Dr Stephen Guest specialises in the diagnosis and treatment of macular degeneration, which he considers one of ophthalmology’s most interesting and major growth areas.  “There has been a lot of research into diseases of the retina, but macular degeneration has been relatively ignored until around five to 10 years ago,” Dr Guest says.  “Macular degeneration is only going to become more prevalent because people are living longer, but now we are seeing more effective treatments and more treatment options in the pipeline.”

THE TYPES
There are two types of macular degeneration: wet and dry.

Wet macular degeneration occurs when new abnormal blood vessels grow from the choroid, the vascular layer of the eye, into the retina.  This causes bleeding, leakage and scarring, resulting in severe loss of central vision.

Dry macular degeneration occurs in older people and may cause a gradual deterioration in reading vision or more sudden deterioration due to haemorrhage or leakage from blood vessels.  Up to 20 per cent of patients with dry macular degeneration develop the wet form, which is rapid in onset and needs to be treated quickly to prevent further visual loss.

The causes of macular degeneration are unknown, although the many contributing factors include age, smoking, poor diet and genetics.  Symptoms include being unable to recognise faces, a blurred patch in the middle of vision, power poles and other straight lines becoming crooked and difficulty reading.

DIAGNOSIS
Diagnosis is straightforward thanks to technology.  “We have powerful new imaging modalities, including non-invasive Optical Coherence Tomography (OCT), so we can see the disease in action and monitor response to treatments,” Dr Guest says.  An OCT uses light to produce very high-resolution, cross-sectional images of the tissue layers within the retina.  Layers at the macula can be studied and measured in microscopic detail.  By comparing the structure and thickness of the layers with a healthy retina, eye specialists can detect wet macular degeneration at an early stage.

TREATMENT
Early detection is vital in saving sight and treatment options depend on the stage and type of the disease.

Dry macular degeneration patients are advised to follow a healthy diet, and in advanced cases, are prescribed vitamin supplements.  Omega-3 fatty acids are important to eye health.  They are found in high levels in the retina and are involved in cell renewal and development.  Omega-3 is found in high concentrations in oily fish such as salmon, tuna, anchovies and sardines.  Research suggests eating fish two to three times per week can reduce the risk of developing macular degeneration and may help slow the progression.  Antioxidants such as lutein and zeaxanthin, vitamins C and E, zinc and selenium are also great for cell health.

Wet macular degeneration is treated by laser or injections. A small number of people have laser therapy to seal blood vessels to stop them leaking under the macula.  The most commonly used injection in New Zealand is Avastin, an effective and relatively cheap antibody treatment which stops small blood vessels leaking.  Treatment frequency varies. In severe cases, people may need an Avastin injection once a month for the rest of their life. Others may need a short series of injections to prevent the disease progressing.  “In 40 per cent of patients treatment improves their vision; in 50 per cent it stabilises their vision and in 10 per cent their vision worsens, whatever we do,” Dr Guest says.
“New treatments are not far away; better treatments that can be administered less frequently.”

EYE HEALTH CHECKLIST:
• Have your eyes tested and make sure the macula is checked
• Don’t smoke
• Control your weight and exercise regularly
• Eat a healthy, well-balanced diet.  Limit intake of fats, eat fish two or three times a week and eat dark, leafy vegetables and fresh fruit daily, and a handful of nuts a week
• In consultation with your doctor, consider taking a zinc and antioxidant supplement
• Protect your eyes from sunlight, especially when young.

By Anne Boswell