Components of the eye

1. ‫اﻟﺮﺣﻴﻢ‬ ‫اﻟﺮﺣﻤﻦ‬ ‫ا‬ ‫ﺑﺴﻢ‬
Dr. Ashraf abdulrhman
MBBS, MSc Anatomy

2. INTRODUCTION
1.
2.
The Eye is the
organ of vision.
Composed of :
Eyeball.
The adnexa.
2

3. 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
3

4. 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
4

5. Eyeball
The three tunics are:
I- An external fibrous tunic
II- A middle vascular tunic
III- An internal tunic
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6. Eyeball
II.

The three tunics are:
I. An external fibrous tunic: that gives form to and protects
the eyeball; it’s the only complete tunic.
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.
6

7. 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.
7

8. 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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9. 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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10. The vascular Tunic
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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11. The vascular Tunic

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 11

12. The vascular Tunic
○
○
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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13. The vascular Tunic
○
○
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.
13

14. 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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15. 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 15

16.  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. 16

17.  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.
17

18. 18

19.  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 19

20.  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.
20

21.  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 21

22.  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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23.  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.
23

24.  The blood supply of the eye:
1.
2.
3.
The arteries can be divided into three groups:
THOSE SUPPLY EYEBLL
SUPPLY OCULR MUSCLES
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.
24

25.  The blood supply of the eye:
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.
25

26.  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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27.  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
-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.
27

28.  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.
28

29.  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 orbita
foramen and innervates most of retractor bulbi and
lateral rectus muscles.
29

30.  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:
- long ciliary nerve of the eye, lacrimal and supraorbital
nerves.
Maxillary division
Zygomatic branch supply ventrolateral segment of the
eyelids and conjunctiva
30

31.  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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