Eye Functions

Lens

A biconvex, crystalline structure which is opaque in preserved eyes. Functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina.

Choroid (Coat)

A darkly pigmented layer directly beneath the retina. Anteriorly, It is continuous with the ciliary body. is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. Provides oxygen and nourishment to the outer layers of the retina.

Retina

A delicate yellowish membrane that is easily separated from the underlying choroid coat. Receives light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition.

Posterior Cavity

A narrow space behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes. The vitreous humor fills the posterior cavity

Sclera

A tough, thick layer beneath the choroid. "White of the eye" and is continuous with the transparent cornea. acts as a tough protection from injury, and provides attachment for the extraocular muscles that move the eye.

Pupil

Functions to regulate the amount of light that enters the eye. When the pupil is smaller, less light enters the eye in bright environments. The pupil gets larger as light levels decrease to let more light into the eye.

Blind Spot

Located in the optic disk. The place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through the optic disc.

Cornea

The cornea acts as the eye's outermost lens. It functions like a window that controls and focuses the entry of light into the eye.

Optic disk

The optic disc represents the beginning of the optic nerve and is the point where the axons of retinal ganglion cells come together. The optic disc is also the entry point for the major blood vessels that supply the retina.

Tapetum Lucidum

The retina has a layer of guanine called the tapetum lucidum, which reflects light and causes the eyes to shine at night when illuminated. (cow or sheep eye) humans do not have this.

Anterior Cavity

The space in the eye that is behind the cornea and in front of the iris. The anterior chamber is filled with the aqueous humor.

Extrinsic eye muscles

These extrinsic eye muscles are some of the fastest contracting and most precisely controlled skeletal muscles in the human body and function. any of six small muscles that control the horizontal, vertical, and rotating movements of the eyeball. somatic nerves

Suspensory Ligaments

Thin transparent fibers that attach the lens to the ciliary body. The ligament functions to support the eye and prevents downward displacement of the eyeball.

Vitreous Humor

This jelly-like substance helps maintain pressure within the eye and holds the retina in place against the posterior wall of the eyeball.

Iris

a darkly pigmented body anterior to the lens which is penetrated by an opening called the pupil. The iris is attached laterally to the ciliary body.. responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. Eye color is defined by that of the iris.

Aqueous Humor

the clear fluid filling the space in the front of the eyeball between the lens and the cornea (leaks out of the cow eye when dissected)

Ciliary body

the part of the eye that connects the iris to the choroid. releases aqueous humor in the eye. The ciliary body also contains the ciliary muscle which changes the shape of the lens when your eyes focus on something.

Optic nerve

transfer visual information from the retina to the vision centers of the brain via electrical impulses. The optic nerve is made of ganglionic cells or nerve cells. It consists of over one million nerve fibers.