As light enters the eye, it strikes receptor cells on the retina called rods and cones. The light triggers a chemical reaction in the cells, which then send electric impulses through the optic nerve to the brain.
Review Date 4/27/2023
Updated by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.