OverviewThe cornea allows light to enter the eye. As light passes through the eye the iris changes shape by expanding and letting more light through or constricting and letting less light through to change pupil size. The lens then changes shape to allow the accurate focusing of light on the retina. Light excites photoreceptors that eventually, through a chemical process, transmit nerve signals through the optic nerve to the brain. The brain processes these nerve impulses into sight.
Update Date 2/27/2013
Updated by: Luc Jasmin, MD, PhD, Department of Neurosurgery, Cedars Sinai Medical Center, Los Angeles and Department of Anatomy, University of California, San Francisco, CA. Review provided by VeriMed Healthcare Network. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.