Retinal fundus: The interior lining of the eyeball, including the retina (the light-sensitive screen), optic disc (the head of the nerve to the eye), and the macula (the small spot in the retina where vision is keenest). The fundus is the portion of the inner eye that can be seen during an eye examination by looking through the pupil.

"Fundus" is the Latin word for the bottom. In medicine, fundus refers to the bottom or base of an organ.