Refractive errors happen when the eye is unable to bend light rays properly. As a result, a clear image cannot be focused in the light-sensitive area of the eye. The primary refractive errors are shortsightedness, farsightedness, presbyopia, and astigmatism. Eyeglasses, contact lenses, or surgery can usually correct such problems. Blurring of the vision is often gradual but can be permanent.

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