Hope for patients with diabetes-related blindness

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Patricia Gibbs’ vision had been dwindling for years by the time it deserted her in a western Sydney street eight years ago—but nothing had prepared the then 50-year-old diabetes patient for the isolation and frustration that would follow.

Forced to give up her license, Gibbs didn’t just lose her sight, she also lost a hefty dose of independence and soon stopped her volunteer work and most of the other activities that had been keeping her busy.

“I was devastated. I laid in bed all day and threw all my clothes away. I thought ‘what the hell am I going to do?’”  Gibbs says.

But her life took an about turn a little more than three years ago when she began receiving treatment known as “intraocular therapy” as part of a randomised control trial at Sydney Eye Hospital.

Last Friday the journal of 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 (Ophthalmology 2006:113(9);1533-1538).

Gibbs was one of the success stories: during the trial she received the treatment in one eye and a placebo in the other and was later given the injections in both eyes. These days she can once again see her grandchildren, she can see to cook, and probably most significantly, she can drive again.

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 it’s 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 percent of eyes, including 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 and Eye Health Institute at the University of Sydney.

That’s where intraocular steroid therapy comes in.

Professor Paul Mitchell, director of ophthalmology at Westmead Hospital, says that while the steroid therapy is unlikely to replace standard laser therapy as the first port of call in treatment because there are significantly more side effects associated with it, it plays an important role for people whose eyes don’t respond to the laser therapy at all, or for whom the problem recurs. (The cost of a steroid injection is slightly less than a standard bout of laser therapy, Gillies and Mitchell say).

In the study patients were given one injection of cortisone every six months and closely monitored for two years. Many patients only need one or two injections, though some need more. After an anaesthetic is put under the film of the eye, doctors use a very fine needle to inject cortisone into the white of the eye—and according to Mitchell (and verified by 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 antiinflammatory 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 control 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 only18 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 only 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 in the retina, 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.

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.

 “The risks can be managed and controlled for—so it’s more ideal for people who have no hope of restoring their vision through other means than just for general patients,” Mitchell says.

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 onto people quickly before the disease is severe,” he says. “If you have good control there’s slow progression and you can prevent needing the treatment at all.”

 

 

 

Preventing Blindness

One in four people with diabetes develop eye diseases that can cause vision loss and blindness. Here are some ways you can decrease your odds.

  • ·        Get screened with a dilated eye exam from an eye care specialist each year
  • ·        Monitor and control your blood sugar levels carefully
  • ·        Quit smoking

 

Source: Sydney Eye Hospital