In the following abnormalities of the eye, which one is a serious condition that leads to blindness?

In the human eye,the fovea is the central point of vision,where:

Aqueous humour is present

Through which of the following does the optic nerve enter the eyeball?

Which of the following statements is correct regarding the pupil of the human eye?
$(I)$. It is the aperture surrounded by the iris.
$(II)$. The diameter of the pupil is regulated by the muscle fibres of the iris.
$(III)$. It is a transparent crystalline structure attached to the ciliary body.
The correct option is:

Differentiation of colour is the property of the cone; it is because of the