Roman Lacheev/Alamy
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A letter chart is only used to find the size of target that the eye can discern. We could easily check if a cheetah were short-sighted
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Helen Blyth
Liverpool, UK
In his answer to this question, Peter Bursztyn writes that he isn’t sure “how one could determine whether a wolf, an eland or a cheetah were short-sighted”. He says: “I can’t imagine devising something like an optometrist’s eye chart for animals.”
As an optometrist, I can tell him we use retinoscopy to determine whether an eye is short-sighted, long-sighted or astigmatic. This technique doesn’t require any input from the subject and would therefore work on a wolf just as well as on a human.
A letter chart is only used to establish the size of target that the eye can discern. This depends on how healthy the eye is, as well as whether it is in focus. So we could easily check if a cheetah were short-sighted, but it would be harder to learn what they can distinguish.
Michael Burrows
Harwell, Oxfordshire, UK
Our flat-coated retriever revealed his short-sightedness on many occasions. The most convincing example was the time he tensed up as a man with a wheeled suitcase approached in the distance. As we got closer, he finally recognised it wasn’t another dog and instantly relaxed.
Alex Harrison
Plettenberg Bay, South Africa
We identified my Australian shepherd dog’s short-sightedness quite early on. Unlike our other dogs, if he detected a family member on the other side of the garden, he would bark angrily as if discovering an intruder. If said family member then called out to calm him, he would immediately recognise them and rush over to greet them. It quickly became very clear that he can’t identify anyone standing about 5 metres or more away by sight, so he therefore has to rely on other senses. He still manages to get by perfectly well, though!
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