what is meant by biochemisty on vision?

Question

history of biochemistry on vision,present status of it

Answer 1

Biochemical reactions that take place in the cells(rods and cones) of retina and neurons that send the sensation to the brain.
Begins withe the works of Late George Wald of Harvard

Answer 2

Since I am not in your class, it is hard for me to know what your homework question actually means or how sophisticated the answer needs to be.

Vision is a process by which photons of light are detected by the retina, converted into chemical signals, processed by the retina, transmitted to the brain, processed by the brain, and the resulting information is assembled into a coherent visual scene by the brain. Biochemistry plays a role at each of those steps.

Probably what your homework refers to, however, is the visual cascade. This is the biochemical process in the photoreceptor neurons of the retina that captures the photons and converts the energy into a chemical signal.

This is a well known and heavily studied process. I am sure you can google it (try 'biochemistry of vision' or 'visual cascade') and find a description that matches the level of your classwork.