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Chapter 11: Eyes

Anatomy and Physiology

Eye is the sensory organ that transmits visual stimuli to the brain for interpretation.

The eye itself is a direct embryologic extension of the brain. Four Rectus and Two

bli!ue muscles attached to the eye. The eye itself is connected to the brain bycranial nerve "C#$ %%& the optic nerve.

External Eye

Composed of the eyelid& con'unctiva& lacrimal gland& eye muscles& and

the bony orbit. rbit contains fat& blood vessels& nerves and supporting nerve

tissue.

Eyelid

Composed of s(in& striated muscle& the tarsal plate& and

con'unctivae.

)eibomian glands provide oils to the tear *lm

Tarsus provides a s(eleton to the lid.+istributes tears over the surface of the eye

,imits the amount of light entering it

-rotects the eye from foreign bodies.

Conjunctiva

Clear& thing mucous membrane.

-alpebral con'unctiva is the part of con'unctiva that coats the

inside eyelids

The bulbar con'unctiva covers the outer surface of the eye and

protects the

anterior surface& with the exception of the cornea and the

surface of the eyelid

in contact with the globe.

Lacrimal Gland

,ocated in the temporal region of the superior eyelid produces

tears that

moisten the eye.

Tears /ow over the cornea and drain via the canaliculi to the

lacrimal sac

and duct and then into the nasal meatus

Eye Muscles

0uperior%nferior

)edial

,ateral rectus nly muscle innervated by the abducens.

0uperior bli!ue only muscle innervated by the trochlear

nerve.

%nferior bli!ue

These muscles are innervated by

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C# %%% "oculomotor$ Controls the levator palpebrae superioris

"2hich elevates and retracts the upper eyelid$ and all

extra ocular muscles

except for the superior obli!ue muscle and lateral rectus

muscle.

C# %3 "trochlear$ 4C# 3% "abducens$

Internal Eye

Composed of three separate layers.

uter wall4 composed of the sclera posteriorly and the cornea

anteriorly

)iddle layer56vea4 Consists of the choroid posteriorly and the

ciliary body5iris

anteriorly.

%nner this layer of nerve *bers is the retina

Sclera

+ense& avascular structure that appears anteriorly as the whiteof the eye.

-hysically supports the internal structure of the eye

Cornea

Constitutes the anterior sixth of the globe and is continuous with

the sclera

ptically clear and has rich sensory innervation and is avascular.

)a'or part of the refractive power of the eye

Uvea

%ris circular& contractile muscular disc containing pigment cells

that produce

the color of the eye. Central aperture is the pupil& through whichlight travels to

the retina. +ilation5contraction controls how much light reaches

the retina.

Ciliary body4 produces a!ueous humor "/uid that circulates

between lens and

cornea$. Contains the muscles controlling accommodation.

Choroid a pigmented& richly vascular layer that supplies

oxygen to the outer

layer of the retina.

Lens

7iconvex& transparent structure located immediately behind theiris.

0upported circumferentially by *bers arising from the ciliary

body.

,ens is highly elastic& contraction5relaxation of the ciliary body

changes its

thic(ness& permitting images from varied distances to be

focused on retina.

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Retina

The sensory networ( of the eye. Transforms light impulses into

electrical

impulses.& which are transmitted through:

ptic nerve: passes through the optic foramen along with the

ophthalmic art5ve Communicates with the brain and the autonomic nervous

system of the eye.

8ccurate binocular vision achieved when image on retina is

fused by cornea5len

Infants and Children

Eyes develop during *rst 9 wee(s of gestation "malformed to maternal drug

ingest5infection

3ision delops through