It is an aldehyde of Vitamin $- A$.

Conjunctiva is a

The eye is developed from which germ layer?

The photosynthetic pigments,viz.,erythrolabe,chlorolabe,and cyanolabe,respectively,are:

The choroid is thin over the posterior two-thirds of the eyeball,but it becomes thick in the anterior part to form the:

The following figure is a diagram showing parts of the human eye. Identify $P, Q$,and $R$ from the options given below.
$\quad\quad P\quad\quad\quad Q\quad\quad\quad R$