IT IS a drug that has made a lot of people very happy, but ironically it might also have made their outlook rather blue.
Men taking high doses of Viagra report seeing a blue haze, but until now nobody has studied whether normal doses of the drug affect vision. And since most people turn off the lights after taking Viagra, such side effects are likely to be under-reported.
Glen Jeffery, at the UK鈥檚 Institute of Ophthalmology in London and four of his colleagues decided to investigate 鈥� all in the name of science, of course 鈥� and took a standard 100-milligram dose of Viagra. 鈥淎 little while after taking it I thought, 鈥榃ho changed the light bulbs,'鈥� says Jeffery.
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To test if the drug disrupted their ability to pick out changes in images against a blue background, the men watched a flashing red circle on a blue screen. Each found that their ability to distinguish very high-frequency flashes from solid patterns was reduced for up to two hours after taking the pill (Current Biology, vol 16, p R44).
Jeffery stresses that any effect will be mild. 鈥淲e don鈥檛 want to scare people into thinking that Viagra turns you blind,鈥� he says.
