Refractive Error

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A refractive error, or refraction error, is an error in the focusing of light by the eye and a frequent reason for reduced visual acuity. An eye that has no refractive error when viewing a distant object is said to have emmetropia or be emmetropic. An eye that has a refractive error when viewing a distant object is said to have ametropia or be ametropic. Refractive errors are frequently categorized as spherical errors and cylindrical errors: Spherical errors occur when the optical power of the eye is either too large or too small to focus light on the retina. People with refraction error frequently have blurry vision. When the optics are too powerful for the length of the eyeball (this can arise from a cornea with too much curvature or an eyeball that is too long), one has myopia.