What causes someone to be nearsighted in one eye and farsighted in another eye?

Check it out: Refractive error (nearsightedness, farsightedness, astigmatism) can naturally be different between eyes. However, there are many eye conditions, such as cataracts which can cause the refractive error of one eye to become significantly different than the other eye. See your ophthalmologist for a complete examination to look into the issue further.