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The eye is a spherical structure which fits in the eye socket in the skull bone. It can be treated as an optical instrument.

The human eye is the organ of vision and light perception.

THE HUMAN EYE

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Six Rectus muscles outside the eye govern its movements. They are the four rectus muscles: 1) lateral, 2) inferior, 3) superior, 4) medial — and the 5) superior and 6) inferior oblique muscles.

The rectus muscles arise from a fibrous ring that encircles the optic nerve at the optic foramen and are attached to the sclera.

HUMAN EYE : RECTUS & OBLIQUE MUSCLES

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Sclera : an opaque layer of the eye that offers a surface for attachment to the intrinsic muscles of the eye. Choroid : part of the Uveal tract extending from the edge of the optic nerve head to the oar serrate. Retina : is a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface.

HUMAN EYE : MAIN LAYERS

CHOROID RETINA SCLERA

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It is triangular in horizontal section and is coated by a double epithelial layer which produces the aqueous humor.

The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes.

HUMAN EYE : CILIARY BODY

CILIARY BODY

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The vitreous humor comprises a large portion of the eyeball. It is a clear gel that occupies the space behind the lens and before the retina at the back of the eye. Because the eye must process visual data, this liquid must be clear enough that light can easily pass through.

HUMAN EYE : VITREOUS HUMOR

OPHTHALMOSCOPE IMAGE OF VITREOUS HUMOR

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The colored part of the eye is called the iris. It controls light levels inside the eye. The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size.

The pupil is the black circle in the middle of the eye. The primary function of the pupil is to control the amount of light entering the eye.

The cornea is the clear, protective outer layer of the eye. Attached to the sclera, it is capable of filtering out some amount of the sun's ultraviolet light.

HUMAN EYE : CORNEA

CORNEA IRIS

PUPIL

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The lens is composed of transparent, flexible tissue and is located directly behind the iris and the pupil.

It can change its curved shape to focus on objects and people that are either nearby or at a distance.

LENS

HUMAN EYE : FOCUSING SYSTEMS

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It transfers visual information from the retina to the vision centers of the brain via electrical impulses through the neural pathway to the brain.

The optic nerve is located in the back of the eye. It is the second of several pairs of cranial nerves.

HUMAN EYE : OPTIC NERVE

OPTIC NERVE

OPTIC NERVE CHASM

OPTIC TRACT

CROSS-SECTION OF BRAIN