The Refractive State of the Human Eye

A large portion of the sensory input to the brain arises from the visual system. Visual function is related to the optical properties of the eye dependeny upon its axial length, the corneal curvature, and the crystalline lens. The optical clarity of the cornea and lens are essential to maintain clear vision. Focusing errors can be corrected by prosthetic devices namely spectacles (in use for over a thousand years) and Contact lenses (In use for over 80 years). Recent surgical innovations allow accurate adjustment of corneal optical power and have become an acceptable alternative. There are however complications and safety issues with all technologies that are used to improve vision.