Pathway of light through the eye
Light first enters the eye by passing through a thin layer of epithelium (the conjuctiva) covering the cornea, then through the cornea where some light refraction occurs. The light then enters the anterior cavity of the eye, passing through the anterior chamber, the pupil, the posterior chamber, and then through the lens. As light passes through the lens, the refraction caused by the cornea is corrected. The pathway continues through the vitreous (posterior) cavity and is focused on the fovea centralis of the macula lutea of the retina.
Light to impulse to vision
Light actually passes through the retina and is reflected by the choroid to the retina again; the rods and cones (photoreceptors of the retina) are oriented on the exterior side of the retina, against the choroid. Photopigments in the rods and cones respond differently to different wavelengths of light received from the choroid. Consequently, they undergo a conformational flux that removes the inhibition on ganglion cells that are otherwise deactivated in the absence of light. The ganglion cells are depolarized and carry an impulse to the optic nerve, then to the occipital lobe of the brain where the impulse is received as an upside down and mirrored image. The brain accommodates for this, and voilà! You see the world before you!