MORE than 1 in 10 New Zealand guide dogs for the blind might themselves be short-sighted. But the good news for owners is that it doesn’t seem to affect their performance.
Like humans with myopia, the dogs see distant objects as blurred because light from them focuses in front of the retina. “If the myopic dogs we identified were children, they’d be wearing spectacles,” says John Phillips, an optometrist at the University of Auckland, New Zealand.
Phillips and his colleague Andrew Collins presented their team’s results this week at a conference on myopia in Cambridge, UK. Of 61 guide dogs tested 13 per cent had myopia.
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The two researchers diagnosed the dogs’ myopia using a retinoscope, which bounces a beam of light off the dog’s retina. Retinoscopy routinely picks up short-sightedness in people.
The dogs were also videoed while tracking black and white targets moving across a screen. The fully sighted dogs performed three to four times as well on this visual acuity test as the myopic dogs. Despite this, the myopic dogs did just as well in standard guide-dog performance tests, such as noticing large objects on the periphery of their vision.
But it may still be better to err on the side of caution when selecting dogs, Phillips suggests. “In traffic, for example, the dogs might not perform as well as fully sighted dogs.”
In the UK, the Guide Dogs for the Blind Association routinely screens its dogs for eye problems, including myopia, a spokesperson said.
