Question: what are the four main parts of the eye?
Answer: Parts of the Eye. Here I will briefly describe various parts of the eye:
Sclera. The sclera is the white of the eye. ... 
The Cornea. The cornea is the clear bulging surface in front of the eye. ... 
Anterior & Posterior Chambers. The anterior chamber is between the cornea and the iris. ... 
Iris/Pupil. ... 
Lens. ... 
Vitreous Humor. ... 
Retina.