Medical Definition of Rod

Rod: A type of specialized light-sensitive cell (photoreceptor) in the retina of the eye that provides side vision and the ability to see objects in dim light (night vision).

By contrast, the cones are the retinal photoreceptors that provide sharp central vision and color vision.

Source: MedTerms™ Medical Dictionary
http://www.medicinenet.com/script/main/art.asp?articlekey=10548
Last Editorial Review: 5/13/2016