Segments and chambers of the eyeball

Anterior segment.
It includes crystalline lens suspended on ciliary body by zonules (suspensory ligaments), iris, cornea and two aqueous humour-filled spaces.

Anterior chamber.
It begins anteriorly just behind cornea and it ends posteriorly just before the anterior surface of iris and part of ciliary body. It contains about 0.25 mL of the aqueous humour communicating with posterior chamber through the pupil.

Posterior chamber.
It starts anteriorly by the posterior surface of iris and part of ciliary body ending posteriorly by the crystalline lens and its zonules with a lateral border of the ciliary body. It contains about 0.06 mL of aqueous humour.

Posterior segment
It includes structures behind crystalline lens including the vitreous humour (a gel-like structure which fills the space behind the lens), retina, choroid and optic disc.

Crystalline lens
It is a flexible transparent biconvex structure enclosed in its capsule, situated immediately behind the iris, in front of the vitreous body. It is suspended in position by the zonules of Zinn that support and attach it to the ciliary body.
At birth, it has equatorial diameter of about 6.5 mm with 3.5–4.0 mm anteroposterior diameter weighing approximately 90 mg. The adult lens typically has equatorial diameter of 9–10 mm with 4 mm anteroposterior diameter weighing approximately 255mg. This proves that the lens continues to grow throughout life. Its accommodative capacity, however, progressively decreases with age finally resulting in presbyopia.
It is made up of capsule, subcapsular epithelium, cortex and nucleus.

Functions
Refraction and focusing of light to the retina for a clear image formation
Blockage of some of the incoming ultraviolet light rays to protect the retina against long-term ultra violet radiation.

Optic nerve
It is the nerve that carries information from the eye to the brain. It is the second cranial nerve (cranial nerve II). The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye. It is the entry point for the major blood vessels that supply the retina.

optic disc