Refractive error is a problem of focusing light accurately on the retina due to the shape of the eye. The most common types of refractive error are near-sightedness (myopia), far-sightedness (hyperopia), astigmatism, and presbyopia. Near-sightedness
results in distant objects being blurry, far-sightedness and presbyopia result in difficulty focusing on close objects, and astigmatism causes objects at all distances to appear blurry.
Near-sightedness is due to the length of the eyeball being too long, relative to the refractive power of the eye. In far-sightedness, the eyeball is too short. In astigmatism, the geometry of the eye creates a different focusing power vertically than
horizontally. Presbyopia occurs as the lens of the eye loses flexibility over time and can not change shape sufficiently. Individuals that have parents with certain refractive errors may be more likely to have similar refractive errors.
An eye exam can diagnose a refractive error and often indicate appropriate treatment options. Refractive errors can be corrected with eyeglasses, contact lenses, or refractive surgery (Lasik).