What does refractive error mean?

Refractive error is a common ophthalmic condition, primarily referring to the inability of parallel light rays entering the eye (without accommodation) to focus clearly on the retina after refraction, instead forming an image either in front of or behind the retina. Clinically, this phenomenon includes three conditions: myopia, hyperopia, and astigmatism. 1. Myopia: In an eye at rest (without accommodation), parallel light rays are focused by the eye's refractive system in front of the retina, resulting in a blurred image. Myopia can be classified into mild, moderate, and high degrees based on severity. 2. Hyperopia: Opposite to myopia, the focal point falls behind the retina, leading to a blurred image. Mild hyperopia may be asymptomatic, but more significant hyperopia or insufficient accommodative ability can impair both distance and near vision. 3. Astigmatism: Related to irregular curvature of the cornea, it causes light rays to fail to converge effectively onto a single focal point after refraction by the eye, resulting in distorted or blurred images.