What is the correct order light must go through to be analyzed by the visual system?

Light is captured, and transduced by the visual system which consists mainly of the eye.

As light passes through the lens via the pupil, retina gets hold of the light that passes through the initial part of the organ. The presence of rods and cones on the surface of the retina enables the eye to process or more specifically transduce this stimuli as a electrochemical signals which can be processed by the brain via the optic nerve. 

the speed increase from w to x due to increased gravity force

the speed decreases from x to y due to decrease in gravity