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Most dengue patients will not be affected by them, while others may not even notice them, but the rare and little-known eye complications brought on by dengue are nonetheless on the rise.
"Dengue has been around for decades, but we hardly saw any of the problems until the last few years," said Dr Stephen Teoh, an ophthalmologist at Tan Tock Seng Hospital (TTSH), who observed 50 affected patients between 2004 and 2005 as part of a study. "As it was so uncommon, few people knew about it."
The most common symptoms are a sudden blurring of vision, and a central patch appearing in one's vision, caused by inflammation and swelling in the sensitive part of the retina. It usually happens about a week after the onset of dengue fever — when patients are usually getting better.
In the worst cases, vision can decline to 6/60 or worse — the equivalent of not being able to read the largest letter on charts used to measure vision.
Between late 2004 and 2005, TTSH saw about 70 to 80 cases of eye complications related to dengue infections. "Prior to this, we only heard about one or two cases every decade," said Dr Teoh. "It's not known why there has been a sudden and sharp increase in the number of cases."
Why the complications occur is also unknown, and there appears to be no particular gender, age or racial group that is more susceptible. Medical treatment appears to have no effect on recovery so far. But there is no need to be alarmed, according to Dr Teoh.
"It's very uncommon, and the complications usually go away by themselves, with or without treatment," he said. "About three-quarters of them recover in three months."
How quickly patients recover appears to depend on how severe the inflammation is at the onset. "For example, if a patient's vision deteriorates to 6/60 at the start, it would easily take up to three months to recover," said Dr Teoh.
So far, the most serious case is a patient who started showing symptoms in 2005, and has yet to recover full vision.
"It is possible that patients may not recover their full vision," he added.
Between late 2004 and 2005, more than 100 cases of eye complications were reported — a "relatively small" proportion of the 14,209 cases of dengue in 2005.
It is estimated that about 5 to 10 per cent of all dengue patients will show some kind of eye complication, but very mild cases usually go ignored by patients.
General practitioners, said Dr Teoh, should inform patients of possible eye complications, so that cases do not unreported. - TODAY/ra
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