Signal transduction- what structure of the eye converts photons of light to an action potential?

What structure of the eye converts photons of light to an action potential?-Depolarized bipolar cells fire an action potential that releases neurotransmitter onto the ganglion cells, which fire an action potential that goes down the optic nerve to the brain. Important parts of eye: cornea, aqueous humor, iris, pupil, lens, vitreous humor, retina.

answer; i believe the correct answer is ( mediation);