Fundus

the back part of the interior of the eye which is visible through the pupil using an ophthalmoscope i.e. the retina and optic nerve.

An ophthalmoscope is an instrument used to view the interior of the eye. It sends a narrow beam of light through the lens of the eye, and contains a perforated mirror and lenses through which the veterinarian can examine the interior or the eye. It can either be hand held or fixed and magnifies the image by a factor of two or more times.