In glaucoma,which of the following occurs?

The iris of the eye is:

The order of three layers of cells in the retina from inside to outside is

Which of the following statements are correct for the iris?
$(I)$. The ciliary body extends forward to form the iris.
$(II)$. It is a pigmented and opaque structure.
$(III)$. It is the visible coloured portion of the eye.
Choose the correct option.

The density of the vitreous humour is approximately equal to that of the:

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