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Steroids Trial Beats Diabetes Blindness

Posted: Wednesday, September 13, 2006

Australian research has proven the effectiveness of a steroid treatment for a type of diabetic blindness.

Last week the journal Ophthalmology published the findings of the two-year research, which found injecting the eye with steroids doubles the chance of improving vision and halves the risk of it getting worse in patients who have diabetic macular oedema, the most common cause of vision loss in people with diabetes.

When a person has diabetic macular oedema, the blood vessels in their eyes deteriorate and leak, causing the retina to swell - which leads to blurred vision and an inability to focus. If left untreated it can ultimately lead to blindness.

Typically, doctors use laser therapy to seal the leaks and slow the swelling, but that treatment fails in about 25 per cent of cases. It had already failed in each of the 43 patients who participated in the Sydney Eye Hospital trial, says the study's lead researcher, associate professor Mark Gillies of Save Sight Institute at the University of Sydney.

"These are the hard-core people with diabetes who go blind, and the steroid injection will rescue many of them," Gillies says. "This is a major advance in treatment, particularly for people with a high risk-profile, and we now have proof that it works. We're not just using haphazard, sloppily collected data and putting vision on the line."

Professor Paul Mitchell, director of ophthalmology at Sydney's Westmead Hospital, says steroid therapy - injected into the eyeballs under local anaesthetic - is unlikely to replace standard laser therapy as the first treatment, because there are significantly more side effects associated with it. But he says it plays an important role for people whose eyes don't respond to the laser therapy at all, or for whom the problem recurs.

One in four people with diabetes could be expected to develop eye diseases that can cause vision loss and blindness, and without treatment, 25 per cent of people with diabetic macular oedema develop vision loss within three years. About 14 per cent of people with diabetes have DMO.

In the Sydney Eye Hospital study, patients were given one injection of cortisone every six months and closely monitored for two years. Many only needed one or two injections, though some needed more. After an anaesthetic is put under the conjunctiva, the thin film covering the white of the eye, doctors use a very fine needle to inject cortisone - and according to both Mitchell and Gibbs the process is virtually painless.

"It doesn't make your eye look or feel any different," Mitchell says. The cortisone seems to have an anti-inflammatory effect on the swelling, although researchers are still not sure how exactly it works - only that it does, Gillies says. The treatment has been used widely in Australia, America and Europe over the last five years, but until now there was no actual proof of its safety or efficacy.

"Until a long-term trial like this we really didn't know how good it was, and the fact that it was sustained over two years means it's probably going to last," Mitchell says. While it may seem simple enough to determine whether a treatment works through observational data, experts say it's not.

"There's a strong placebo effect in macular diseases, and there have been several instances where randomised controlled trials have found commonly-used treatments did not work, and one case where the treatment actually made things worse," Gillies says.

Another study by Gillies and the Save Sight Institute published in Archives of Ophthalmology found no benefit at all to using the steroid therapy to treat another disease called macular degeneration - despite the fact that, as in this case, doctors had already been doing so for some time (2004:122(10);1571-20).

But for diabetic macular oedema the injection treatment improved vision in 56 per cent of eyes, compared with just 26 per cent of those who received the placebo. Likewise, only 18 per cent of steroid-treated eyes got worse over the two-year period, compared to 37 per cent of the placebo-injected eyes.

Intraocular therapy is not a miracle cure. The study found substantially more side effects in the steroid-treated eyes than those that were injected with a placebo. Fifty-four per cent of the treated eyes developed cataracts that had to be surgically removed, while none of the placebo group developed cataracts during the two years. "They develop more quickly because of this - it's a risk anyway in these patients, but this hastens it," Mitchell says.

The study also found much higher risk of raised pressure inside the eyeball, a risk factor for glaucoma if it goes untreated (68 per cent of treated eyes developed increased pressure, compared with only 10 per cent of the eyes that were injected with the placebo).

Less common, but still a potential problem, is a 1 in 400 chance of infection. But, the upside, according to both Gillies and Mitchell, is that the side effects are manageable. For example, raised pressure is treatable with eye drops, and cataracts can be removed.

Equally though, he says most such desperate situations can be avoided in the first place through properly controlling diabetes and getting your eyes screened.

"You need to have your eyes checked regularly if you have diabetes. The best results are when we get on to people quickly before the disease is severe," he says.

Source: Diabetes In Control: "If you have good control there's slow progression and you can prevent needing the treatment at all." journal Ophthalmology (2006:113(9);1533-1538).