Refractive error

A vision condition in which the eye does not focus light correctly on the retina, causing blurred vision. Its main forms are myopia, hyperopia, astigmatism, and presbyopia.

Cornea: The transparent front surface of the eye that supplies most of its focusing power. Its curvature strongly affects where incoming light converges.
Myopia: A refractive condition in which distant objects focus in front of the retina. It is the common nearsighted form of refractive error.
Eyeglasses: Wearable lenses that correct vision by changing the path of incoming light. They are the most familiar way to compensate for refractive error.
Visual acuity: A measure of the eye’s ability to distinguish fine detail, commonly tested with an eye chart. Uncorrected refractive error often reduces measured distance or near acuity.
Crystalline lens: The transparent, flexible structure behind the iris that adjusts focus by changing shape. Its shape and focusing power help determine whether light reaches the retina sharply.
Hyperopia: A refractive condition in which light would focus behind the retina without accommodation. It is the farsighted form caused by insufficient focusing power relative to eye length.
Contact lens: A thin corrective lens placed directly on the eye’s surface. Its position on the cornea provides an alternative to eyeglasses.
Amblyopia: Reduced vision in one or both eyes caused by abnormal visual development during childhood. Uncorrected childhood refractive differences can disrupt visual development.
Retina: The light-sensitive tissue lining the back of the eye that converts images into neural signals. Refractive error is defined by light failing to focus on this surface.
Astigmatism: A refractive condition in which unequal curvature produces different focus in different meridians. It creates directional blur rather than one uniform focal point.

Linked from 18 pages