The major parts of the eye and their functions are summarized in the following chart:
| Structure |
Function |
| Sclera |
Maintains shape of eye; protects eyeball; site of eye muscle attachment |
| Cornea |
Refracts incoming light; focuses light on the retina |
| Pupil |
Admits light |
| Iris |
Regulates amount of incoming light |
| Lens |
Refracts and focuses light rays |
| Aqueous humor |
Helps maintain shape of eye; maintains introcular pressure; nourishes and cushions cornea and lens |
| Ciliary body |
Holds lens in place; changes shape of lens |
| Vitreous humor |
Maintains intraocular pressure; transmits light to retina; keeps retina firmly pressed against choroids |
| Retina |
Absorbs light; stores vitamin A; forms impulses which are transmitted to brain |
| Optic nerve |
Transmits impulses to the brain |
| Choroid |
Absorbs stray light; nourishes retina |
The accessory structures of the eye include the eyebrows, eyelids, eyelashes, conjunctiva, and lachrymal apparatus. These structures have several functions, including protecting the anterior portion of the eye, preventing the entry of foreign particles, and keeping the eyeball moist.
