Can a person be short-sighted in one eye and long-sighted in the other?

It's unusual, but a person can indeed be short-sighted in one eye and long-sighted in the other. There are two medical terms used to describe this condition: antimetropia and anisometropia.

Antimetropia is the technically accurate term when describing one eye being short-sighted and the other being long-sighted, but the way it affects your vision means optometrists may choose to use the term anisometropia for this condition.

Anisometropia is where the two eyes have significantly different refractive (light-bending) powers. If your optometrist says you have anisometropia, the lens power for one eye on your glasses prescription will differ from the lens power for the other eye.

In simple anisometropia one eye has no prescription while the other can be log or short sighted. In complex anisometropia, both eyes may be short-sighted, or long-sighted, but have very different powers. As already mentioned one eye short-sighted and the other long- sighted is the specific condition antimetropia.

Anisometropia symptoms

A person with anisometropia or antimetropia will see noticeably unequal blur in the two eyes at different distances. Also, it’s common for uncorrected anisometropia to cause poor depth perception, headaches, dizziness and even nausea.

In many cases, to reduce these symptoms, the brain will quickly learn to favour the eye with the smaller refractive error, this can result in the development of amblyopia in the other eye.

When unequal refractive errors are corrected with spectacles, a person with anisometropia will notice that objects seen by one eye will look larger or smaller than the same objects viewed by the other eye. This difference in image sizes is called aniseikonia. This, too, can cause problems with depth perception, headaches, dizziness and visual discomfort.

Treatment of anisometropia

Early diagnosis and treatment of anisometropia are critical so the brain doesn't ignore the weaker eye and cause irreversible amblyopia. Routine children's eye exams for kids prior to going to school and once at primary school are essential to rule out anisometropia and ensure normal visual development.

Since contact lenses are very thin and rest directly on the surface of the eye, they cause little or no aniseikonia and can sometimes provide more comfortable, natural-appearing vision than spectacles for people with anisometropia.

LASIK is another option to correct significantly dissimilar refractive errors in the two eyes and avoid aniseikonia. However, this option should be considered only after the refractive errors (particularly the short-sightedness) are stable — generally after age 20.

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