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External and internal eye anatomy

The 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.

External and internal eye anatomy

Review Date: 1/29/2024

Reviewed By: Audrey Tai, DO, MS, Athena Eye Care, Mission Viejo, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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