Body part containing photoreceptors

RETINA

This light-sensitive layer at the back of the eye converts images into signals the brain can interpret, much like film in a camera.

This clue is a straightforward definition pointing to the part of the eye that detects light. The retina is the thin layer at the back of the eyeball packed with photoreceptors—rods and cones—that convert light into signals for the brain. No wordplay here, just a direct reference to the biological structure responsible for vision.