Dear Doctor: Can Cats have Bad Eyesight?
Q I have suffered from nearsightedness for my entire life. Lately, I’ve been wondering if our cats can have vision problems too (outside of eye disease or something related to the aging process, like cataracts). If so, is there a way to determine this?
Michael R. Cunningham
A Dear Michael: Nearsightedness is a type of vision problem known as a refractive error. The structures of the eye are meant to act as a giant lens, bending incoming light rays to focus images clearly on the retina. When a refractive error is present, the eye is not bending light properly. In the case of nearsightedness (also known as myopia), light rays are focused in front of the retina. In the case of farsightedness (also known as hyperopia), light rays are focused behind the retina. In either case, the result is blurry vision.
Refractive errors can result from abnormalities in the composition or shape of various parts of the eye, or because the eyeball is abnormal in overall length. In people, most refractive errors are easily corrected with glasses or contact lenses, which alter the path of light entering the eye and allow for light to be focused properly on the retina.
Refractive errors are assessed via a technique called streak retinoscopy, in which a beam of light is swept across the eye and its movement observed. Through this technique, ophthalmologists can determine which type of refractive error is present and can calculate the proper prescription for glasses or contact lenses.
Animals can also have refractive errors. Several studies have been done to assess dogs, cats and horses for refractive error. These studies found that most animals have very little refractive error, although certain dog breeds were found to be near- or far-sighted. Adult cats seem to have minimal refractive error. While other eye problems like cataracts or retinal diseases can impair feline vision, your cat probably doesn’t need glasses!
Stephanie Pumphrey, DVM, DACVO
Cummings School of
at Tufts University