Anatomy of The Eye
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INTRODUCTION

The Eye is the
organ of vision.

Composed of :
1. Eyeball.
2. The adnexa.
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THE POSITION

In the Predatory species:
have set well forward

In Herbivores ,
Ruminant and rabbits:
have eyes more laterally
to have wide area of
vision
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Terminology of the eye




Cornea : the transparent
part of the eyeball .
Anterior pole: the highest
point on cornea .
Posterior pole : the
highest point on posterior
surface .
Optic axis: the straight
line passing through both
poles
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The Eyeball

Equator :an imaginary line about
the eyeball, which is the
equidistant from the poles.

Meridian: is one of many lines
passing from pole to pole that
intersects the equator at right
angles.
• Optic nerve :leaves the
eyeball slightly ventral
to the posterior pole
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Eyeball
The three tunics are:
I- An external fibrous tunic
II- A middle vascular tunic
III- An internal tunic
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Eyeball
The three tunics are:
I. An external fibrous tunic: that gives form to and
protects the eyeball; it’s the only complete
tunic.
II.
A middle vascular tunic: that consist largely
of blood vessels and smooth muscle

concerned with the nutrition of the
eyeball and the regulation of the
shape of the lens and size of pupil.
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Eyeball
III. An internal tunic: that consists largely
of nervous tissue
 concerned with vision and translation of
visual stimuli into nerve impulses for
interpretation by the brain.
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The Fibrous Tunic
It consists of the sclera and the cornea,
which meet at the limbus.
1. The sclera is the opaque posterior part of
the fibrous tunic and consists of a dense felt
work of colagenous and elastic fibers and is
generally white but in some species it
contain pigment cells

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The fibrous tunic
The cornea forms about one quarter of the
fibrous tunic and bulges forward. It is
composed off dense connective tissue
arranged in lamellar form .
 The cornea doesn’t contain blood vessels;
nutrients for its cells permeate from vessels
in the limbus or are carried to it its surface
in the lacrimal fluid and aqueous humor .

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The vascular Tunic (uvea)
Deep to the sclera, which it composed of
three zones .
1) The choroids: lies on the sclera from the
optic nerve to the limbus and contains a
dense network of blood vessels embedded
in heavily pigmented connective tissue

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The vascular Tunic (uvea)


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In the dorsal part of the fundus the choroids forms colored,
light-reflecting area known as tapetum lucidum
 is avascular layer (cellular in the carnivores, fibrous in
ruminants and horses) between the capillaries and the
vessels.
The tapetum makes the eyes of animals shine when they
look toward the light.
Our eyes and those of the pig don’t have a tapetum so they
don’t reflect the light.
This reflecting of light is a night vision adaptation because
of stimulation of the light sensitive receptors in the retina.
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The vascular Tunic (uvea)
2) The ciliary body :
toward the limbus the choroids
thickness to form it.
3) The Iris: the smallest part of the
vascular tunic, which extends from
the cornea to the lens.
 It attached to sclera and ciliary
body by pectinate ligament.
 the opening in the center is the
pulpi
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The vascular Tunic (uvea)

The iris divided the space between the
lens and cornea into anterior and
posterior chambers tat communicate
through pupil and filled with, aqueous
humor (a clear watery fluid).

The color of the iris determines the
color of the eye
 depends on the number of the
pigmented cells present in its
stroma
 the type of the pigment in the
cells.
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The internal tunic

The internal tunic of the eyeball contains
the light-sensitive receptor cells (known as
retina).
 It’s an extension of the brain to which
remains connected by the optic nerve.
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The internal tunic
The layers in retina are:
 A single layer of pigmented cells.
 Aneuroepithelialm layer containing the
receptor cells, rods and cones and their
nuclei.
 the rods for black and whit
 the cones for the color vision.
 A layer of bipolar ganglion cells.
 A layer of multipolar ganglion cells
nonmyelinated axons lying internal to the
cells and pass to the optic disc where they
form the optic nerve.
 The optic disc is a blind area because there
is no receptor cell.
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v The adnexa of the eye
1.
The orbital fasciae :
a. The periorbital: is attached
near the optic foramen at the
apex of the cone .
b. The superficial muscular
fascia: lies within the
periorbital. It’s loose and fatty.
And envelops in the levator
palpebrae superioris and the
lacrimal gland.
c. The deep muscular fascia: is
more fibrous and arises from the
eyelids and from the limbus of
the eyeball.
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v The adnexa of the eye
2. The muscles of the
eyeball:
 The rectus muscles: dorsal,
ventral, medial and lateral
are inserted anterior to the
equator by wide but very
thin tendons.

The ventral and dorsal
oblique muscles: attach to
the eyeball near the equator.
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v The adnexa of the eye
2. The muscles of the eyeball:

The retractor bulbi arises
from the vicinity of the
eyeball and inserted on the
eyeball posterior to the
equator.

The levator palpebrae
superioris: striated muscle
within the orbit that doesn’t
attach to the eyeball but
passes over it to enter and
elevate the upper eyelid
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v The adnexa of the eye
3. The eyelids and conjunctiva :
 The eyelids (palpebrae) are two
musculofibrous folds of which
the upper is the more extensive
and more mobile.

The free margins of the lids are
meet at the medial and lateral
angles of the eye and bound an
opening known as the
palpebral fissure.
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v The adnexa of the eye
3. The eyelids and conjunctiva :
They are consist of three layers:
1.The skin: is thin and delicate and is
covered with short hairs: it may also
carry a few prominent tactile airs.
2.The musculofibrous layer: is formed
by the orbicularis oculi, the orbital
septum, the aponeurosis of the levator
muscle and the smooth tarsal muscle.
3.The mucous (palpebral conjunctiva) a
thin, transparent mucous membrane
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v The adnexa of the eye
3. The eyelids and
conjunctiva :
 The third eyelid is
supported by a T-shaped
piece of cartilage.
 Bar lies in the free edge of
the fold and stem points
backward into the orbit
medial to the eyeball.
 The stem of cartilage is
surrounded by lacrimal
gland (the gland of the third
eyelid).
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v The adnexa of the eye
4.

The lacrimal apparatus:
This consists of lacrimal gland
proper

The lacrimal gland is flat and
lies between the eyeball and the
dorsolateral wall of orbit.

The glands associated with the
third eyelids

several small accessory glands
•
duct system that conveys the
lacrimal fluid after it has
washed over the eye into the
nasal cavity for evaporation.
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v The blood supply of the eye:

The arteries can be divided into three groups:
1.
THOSE SUPPLY EYEBLL
2.
SUPPLY OCULR MUSCLES
3.
THOSE LAEVING THE ORBIT TO SUPPLY
ADJCENT STRCTURES.

The external ophthalmic artery carries the
principle supply of the blood to the eye, which is
a branch of the maxillary artery.
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v The blood supply of the eye:
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1) The branches of the external
ophthalmic for the eyeball penetrate
the sclera to reach the vascular
tunic and retina.
-Short posterior ciliary a. / supply
the adjacent choroids in addition to
branches to the optic nerve.
-Long posterior ciliary a. /pass
close the sclera closer to the
equator.
-The anterior ciliary a. / supply
the anterior potion of the choroids,
the ciliary body and the iris
These arteries anastomose to form
the greater arterial circle of the
iris.
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v The blood supply of the eye:
2) The arteries that supply the ocular muscles.
Which the absence of the large vessels in
distal ends reduces bleeding when the
muscles are cut during the enucleating.
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v The blood supply of the eye:
3) The arteries that leave the orbit:
 -The lacrimal a. / supply the lacrimal gland in
route.
 -The supraorbital a. / send branches to the upper
eyelids
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
-The malar a. /supply the eyelids and also
adjacent area of the face.
-The external ethamoid a. / supply the ethamoid
labyrinth of the nasal cavity.
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v The nerve supply of the eye:
The optic nerve II: enters the orbit through the
optic foramen and passes to the light receptor
cells in the retina.
 It allows the movements of the eye and is
covered by meninges that it acquired during its
development.

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v The nerve supply of the eye:

The Oculomoter nerve III: control the movement of the
eyeball. it enters the orbit through the orbital fissure.
 Supply: dorsal, medial, ventral Rectus muscle
 Ventral oblique muscle
 Part of retractor muscle

The abducent nerve VI: enters through the orbital
foramen and innervates most of retractor bulbi and lateral
rectus muscles.
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v The nerve supply of the eye:

The trochlear nerve IV: innervate

Dorsal oblique muscle

The trigeminal nerve V: send branches to the eye.
 Opthalmic division
Give sensory branches to:
1- long ciliary nerve of the eye, lacrimal and supraorbital
nerves.
 Maxillary division
 Zygomatic branch supply ventrolateral segment of the
eyelids and conjunctiva
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v The nerve supply of the eye:

The facial nerve VII:
 passes between the eye and the ear gives
auriculopalpebral branch

innervates the orbicularis oculi
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