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Imagine opening your eyes and looking at a world that is blurred and distorted. Fortunately, ongoing research into the cause and treatment of some eye conditions offers hope of a major breakthrough for saving failing sight. Family Health Diary reports.

Science and technology has advanced so much recently that illnesses and ailments once thought to be untreatable are now on the brink of the long-awaited “miracle” cure.

In the field of eye research there has been a remarkable increase in studies using gene therapy to treat conditions such as melanoma of the eye, inherited blindness in children, and degenerative diseases of the retina that can cause blindness.

Gene therapy works by using the Trojan Horse principle, whereby a harmless virus carrier inserts “good” genes into defective eye cells to replace faulty genes, and restore normal eye function.

But there are also a number of routine procedures, now used on a regular basis, that offer solace to anyone losing their sight. Here’s just a glimpse of some serious eye conditions and what may be done about them.

NEW DEVELOPMENT FOR INHERITED BLINDNESS
Leber congenital amaurosis (LCA) is an inherited disease of the retina, caused by abnormal development or premature degeneration of the retina. It is characterised by severe loss of vision or total blindness at birth or soon after. Other eye-related abnormalities occur with this disease, including involuntary roving eye movements, deep-set eyes, and sensitivity to bright light.

Research carried out at various centres, including The Johns Hopkins Centre for Hereditary Eye Diseases and Harvard Medical School, has discovered there are several genes associated with LCA. Researchers have been working with one
of these genes, the RPGRIP gene, to develop gene replacement therapy, which has been tested successfully in animal models (mice and dogs).

In May this year, University College London announced a new clinical trial using gene therapy in young adults and children with inherited blindness.

Preliminary results are expected within a few months, and according to trial leader and eye specialist Professor Ali, “they are likely to provide an important basis for many more gene therapy protocols in the future”.

MACULAR DEGENERATION
Age-related macular degeneration (AMD) is more common in women than men and is the leading cause of blindness in western society. AMD is a degenerative disease that affects the macula region of the retina (responsible for central and detailed vision) resulting in distortion, blurring and loss of central vision.

The disease usually affects older people and is known to be linked to smoking, obesity and poor diet. The “wet” form of the disease is less common but more severe and accounts for 90% of all AMD-related blindness. It is caused by abnormal growth of blood vessels into the retina, which can become “leaky” and eventually cause scarring and loss of central vision.

Wet AMD can be improved by laser treatment to seal the leaking vessels.

Lucentis, which is an antibody that targets abnormal blood vessels and prevents their growth, was approved in 2006 for use in treating AMD. Injection of lucentis into the retina has been successfully used, and according to Dr Peter Hadden, a specialist opthalmologist at Auckland’s Eye Institiute, it’s been a big improvement on previously available treatments.

The “dry” form of the disease, caused by breakdown of retinal cells, cannot be treated yet, although usually it doesn’t lead to such severe loss of vision as the “wet” form.

GLAUCOMA
A build-up of fluid in the eye chamber can cause increased pressure, damage to the optic nerve (nerve fibres that take messages to the brain) and loss of vision.

Glaucoma occurs in 2% of men and women over the age of 40 years, but 10% of those over the age of 70, so the incidence increases significantly with age.

There is a definite hereditary factor and a child may be born with congenital glaucoma.

Glaucoma is an insidious disease and can sneak up unsuspected, since there are often no symptoms until damage is advanced and vision already impaired. However, says Auckland Eye Institute glaucoma specialist Dr Danesh-Meyer, early
symptoms can be detected with regular glaucoma assessments that include pressure measurement, a visual field test and an assessment of the optic nerve at the back of the eye. If detected in time, glaucoma is easily treated with eye drops to reduce pressure and save the optic nerve from damage.

DIABETIC RETINOPATHY
Diabetic retinopathy affects approximately 4% of the European New Zealand population (similar figures to those in the UK and USA) and 12% of the Maori and Pacific Island New Zealand population, based on known cases in 2003. However, the actual incidence in both groups is probably twice the reported rate.

Diabetic retinopathy is a complication of type-2 diabetes and is a degenerative condition of the retina, where high blood sugar causes damage to the blood vessels which can burst and leak, causing deposits on the retina.

Diabetic retinopathy can become a serious problem, where abnormal blood vessels grow to replace damaged vessels. Vision will be lost unless treated and the best form of treatment is to keep diabetes under control. Laser treatment can stop the progression of the disease, but cannot restore sight already lost.

Dr Hadden uses vitrectomy surgery in some cases to restore sight that has been lost. This technique is not new but has become more successful in recent years due to new technical developments in ophthalmology. This involves removal of the gel-like filling of the eye cavity that has become clogged with blood and debris from damaged retinal blood vessels.

CAN DIET AFFECT VISION?
At the moment there is “not enough proof for the general population to recommend particular foods or vitamins/minerals” according to Dr Peter Hadden, however new evidence suggests that certain nutrients may help maintain vision in people already seriously affected by AMD.

GOOD FATS PROTECT EYES
Essential fatty acids in the diet may have a role to play in preventing progression of AMD, based on the results of recent studies in mice. These suggest that increasing the amount of omega-3 fatty acids (found in fish oils, particularly deep sea cold water fish such as salmon and mackerel) may protect eyes against retinopathy, a condition which occurs in diabetics, in macular degeneration and in premature babies.

Scientists in the US and Sweden, led by Dr Lois Smith of the Children's Hospital Boston, found a 50% decrease in retinopathy in mice fed with more omega-3 fatty acids. The same could not be said for omega-6 fatty acids, which were actually found to contribute to the growth of abnormal blood vessels in the retina.


                                             

SPINACH PROTECTS EYESIGHT
Popeye may have been right after all. Eating spinach is good for you, not because it makes you strong, but because it contains chemicals that may protect the eyes from age-related macular degeneration (AMD).

Leutein and zeaxanthin, which are also found in broccoli and sweetcorn, are antioxidants which concentrate in the eye and form an oily substance called xanthophyll that is thought to protect the macula of the eye from degeneration. Since these chemicals cannot be made by the body they only come from the diet and are then stored in the macula.

Scientists at Manchester University are about to launch a study to discover whether eating more of these vegetables will actually slow down the process of macular degeneration.

THE AGE-RELATED EYE DISEASE STUDY
In 2001, the results of a study sponsored by the National Eye Institute in the US; the Age-Related Eye Disease Study (AREDS), reported that taking a combination of zinc and antioxidants reduced the risk of AMD worsening and progressing to a more advanced stage. In contrast, the study found no beneficial effect on cataract conditions.

The National Eye Institute is now about to launch AREDS II to try and improve the original formula by adding the yellow-pigmented antioxidants, lutein and zeaxanthin to the study formulation, along with omega-3 fatty acids (derived from fish oils).

by Janet Marianne Jackson

WHAT IS 20/20 VISION?

This is a way of expressing normal eyesight based on the clarity or sharpness of vision (visual acuity) when measured at a distance of 20 feet. If you have less than “perfect” eyesight then you may need to stand at 20 feet to see what others can see at 100 feet, in which case you are said to have 20/100 vision.

It is unusual for humans to have better than 20/20 vision, however, some birds of prey, have extreme visual acuity up to 20/2, which is needed to see small objects when flying high above them.

The eye essentially works like a camera. Light coming into the eye passes through the cornea (front of the eye), on to the lens and then focuses on the retina. If the eyeball is too long or too short then light is either focussed in front of or behind the retina, which results in short-sightedness (myopia) or long-sightedness (hyperopia).
  
If the lens or cornea is misshapen this can interfere with seeing clearly at any distance and is called astigmatism. As we age, the muscles in the eye weaken and the lens becomes less flexible, which causes it to change shape; it is then harder for the eye to focus close up. This is called presbyopia and usually affects people over 40.

Each of these conditions can easily be corrected using glasses or contact lenses, which refocus light onto the back of the eye. Laser treatment can also be used to correct vision by reshaping the eye.

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