As light enters the eye, it strikes the receptor cells of the retina called the rods and cones. A chemical reaction results in the formation of electric impulses, which then travel to the brain through the optic nerve.
Update Date 5/11/2015
Updated by: Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.