Download Anatomy and Physiology of The Eye

Anatomy and
Physiology of The Eye
By
Hesham M. El-Toukhy
Ass. Prof. of Ophthalmology
KFU, KSA
• Ophthalmology. A Short Textbook by F.
Hollwich, Thieme Verlag Stuttgart, Germany.
• Lecture notes on ophthalmology. Bruce
James, Chris Chew, Anthony J. Bron,
Blackwell publishing.
• Clinical ophthalmology: A Systemic approach
By: Kanski Jack 3, Butterworth-Heinemann.
- Orbit
- Eye Lids.
- conjunctiva.
- Lacrimal apparatus:
Lacrimal gland.
Lacrimal drainage system.
- Extraocular muscles.
- The globe and visual pathway.
The orbit ‫ فورمن اهميتها تربط‬3 ‫فيه‬
‫االوربت كفتي بأذر كفتي في السكل‬
Pear shaped
cavities.
Apex (within optic
canal) directed
posteriorly,
medially, and
slightly upwards.
Formed of 7 bones:
frontal, zygomatic,
maxilla, palatine,
lacrimal, ethmoid,
and sphenoid.
Periorbita (orbital fascia) at base
-orbit cavity is pyramidal in shape .its apex is
goes posteriorly.angle=90 between superior and
inferior fissure
-foramin in orbita cavity:1-optical canal.2superior and inferior fissure
-periostium at anterior margin is called
periorbital which is thicken with eye lid to form
orbital septum then became more thicker to form
tarsal plate
-skeleton of eye lid are orbital septum and tarsus
plate {{at base
•
•
•
•
Orbital apex.
Common tendinous ring
(annulus of Zinn)
Orbital contents
- Eye ball
and optic
nerve
-Muscles:
Levator
superioris,
the 6
Extraocular
Muscles
- Nerves and
blood
vessels (no
lymphatic)
-Lacrimal
apparatus
-Orbital fat
The Lid
1-skin
2-subcutaneous tissue.
3-orbicularis occuli muscle.
4-orbital septum and tarsal plate.
5-conjunctiva.
-Aponeurosis
of levator
palpebrae superioris muscle in
upper eye lid. << ‫هذا الي يفرقه عن اللور‬
-smooth muscle (upper and lower tarsal muscles).
Lid margin:
Cilliary portion.
Lacrimal portion.
No cillia here
Opening of tarsal
(meibomian)
glands.
Gray line: junction
between ant. Part
(skin and muscle)
and post. Part
(tarsus and
conjunctiva).
• Blood supply: medial palpebral (of
ophthalmic) and lateral palpebral (of
lacrimal of ophthalmic) arteries.
• Lymphatic drainage: superficial parotid
and submandibular nodes.
conjuctiva
• Is a thin mucous
membrane that lines
the eye lids and is
reflected at the
superior and inferior
fornices onto the
antirior surface of the
eye ball.
• The conjunctival
epithi. Is continuous
with the epidermis at
lid margin and with
corneal epithelium at
the limbus. Thus
forming a potential
space; the
conjunctival sac.
For purpose of description, It is
divided into:
palpebral conjunctiva, fornical
conjunctiva, bulbar conjunctiva and
plica semilunaris.
• Palpebral conjunctiva : firmly adherent to
the tarsus. Sulcus subtarasalis is a
shallow groove on the back of the eye lid
2mm from post. Lid margin.
Histologically, the conjunctiva is formed
of 2-5 layers of stratified columnar epith.
Resting on loose connective tissue.
• Goblet cells are scattered along the
surface of the conjunctiva, it secretes the
mucous component of the tear film.
• Accessory lacrimal glands situated in the
connective tissue of the conjunctiva.
• Blood supply of the conjunctiva comes from
the palpebral vessels of the eye lid that
supply palpebral conjunctiva, fornical
conjunctiva (posterior conjunctival arteries),
and bulbar conjunctiva reaching for 3mm
from the limbus, where they anastomose
with the anterior conjunctival arteries which
are branches of the anterior cilliary arteries.
• Lymphatic drainage: to superficial parotid
and submandibular nodes.
Orbital septum and tarsal plate
Orbital
septum is the
framework of
the lid.
Attached to
orbital
margin.
Separates lid
from orbital
cavity.
Become
thickened to
form the
tarsus.
Tarsal glands (meibomian gl.) 20-30 embedded in
the substances of the tarsus in postirior wall .
Opening at lid margin.
Orbicularis
oculi:
-close eye
Lid >> most
importanant
-dilates
lacrimal sac
(suction of
tears).
Nerve supply: facial (7th) N enter the muscle from
temporal side.
Levator
palpebrae
superioris :
only in the upper eye
lid.
Function: elevation
of the eye lid.
Insertion: -aponeurosis into the upper edge of tarsus
(smooth muscle of tarsus), ant. surface of tarsus ( also
skin. -Medial and lateral expansion of aponeurosis into med. and lat. palpeb
ligaments. –upper conj fornix).
Nerve supply by superior branch of oculomotor (3rd)N.
part which is smooth muscle of the tarsus: sympathetic Ns from superior
cervical sympathetic ganglion.
Origin from apex of eye lid
Lacrimal gland
lies in the anterior upper temporal part of
the orbit
Consists of
large orbital
part and small
palpebral part
that are
continuous
with each
other around
the apenorosis
of the levator
Ms.
Lacrimal gland
• Ducts from the orbital part and plapebral
part open in the superior fornix.
• Blood supply: lacrimal artery of
opthalmic artery.
• Lymphatic drainage: with conjunctival
drainage to superficial parotid nodes.
Lacrimal drainage system
- 2 Lacrimal puncti
on the summit
lacrimal papillea.
- 2 Lacrimal
canaliculi each
has vertical and
horizontal portion.
- Lacrimal sac:
has fundus , body,
and neck.
- Nasolacrimal duct: connects sac with inferior meatus
of the nose. Directed downwards, backwards, and
laterally.
The Exrtraocular Muscles
There are 6 extraocular muscles:
4 straight muscles (4 recti)
1- superior rectus. 2- inferior rectus.
3- medial rectus. 4- lateral rectus.
2 0blique muscles
1- superior oblique.
2- inferior oblique.
Origin of extraocular muscles
5 arise from
the apex of the
orbit except
the inferior
oblique.
The 4 recti:
from annulus
of zinn
(common
tendinous
ring).
The superior oblique: above and medial to the
annulus of Zinn.
Orbit, ant. View
0rigin of Inferior oblique
The inferior
oblique: the only
muscle that
originates from
the anterior part
of the orbit)
shallow
depression in
the floor of the
orbit lateral to
the fossa for
lacrimal sac.
Insertion of extraocular muscles
All are inserted in the sclera.
The 4 recti muscles are inserted into
the sclera anterior to the equator
close to the limbus.
The oblique muscles are inserted into
the sclera, posterior to the equator at
the posterior temporal part of the
sclera.
Insertion of the 4 Recti (right
Eye)
In the
sclera
anterior
to the
equator
(spiral of
Tillaux >>
junction
bettwen
cornea
and
seclera ).
Insertion of the oblique muscles
in the sclera posterior to the equator (right
Eye).
Superior
oblique:
upper post.
Lateral
part.
Inferior
oblique:
lower post.
Lateral part
• Blood supply from muscular branches of
ophthalmic artery (2 for each muscle
except LR only one).
• Nerve supply : all by 3rd nerve
(occulomotor) except:
Lateral rectus by Abducent nerve. (6th).
Superior oblique by trochlear (4th) nerve.
Uniocular eye movements
A- elevation
B- depression C- adbuction
d- adduction E–extortion >> away from the
nose
F- entortion
The horizontal recti
The medial rectus:
Arise from annulus of zinn, inserts 5.5
mm from the limbus on the medial side
of the globe.
Its sole action is adduction.
The lateral rectus:
Arise from annulus of zinn, inserts 6.5
mm from the limbus on the lateral side
of the globe.
Its sole action is abduction.
The vertical recti
The vertical recti run in the
same direction of the orbital
axis. So they form angle of
23° with the optical axis.
Orbital
axis
Axis of
vertical
recti
Optical
axis in
primary
position
Axis of
oblique
recti
The superior rectus main
(primary) action in the
primary position is
elevation.
Secondary actions are
adduction and intortion.
In position of 23°
adbuction the only action is
elevation. (optimal position
for function testing)
In position of 67° adduction
the only action is intortion.
(the line of pull of the
Action of right SR
muscle makes 90 degree
with the optical axis).
The inferior rectus main action in
the primary position is
depression.
‫ لو كانت فور‬Secondary actions are
‫وورد ونوت برلل مع االكسس حق االي بول لها‬
adduction and ‫ثالث حركات‬
extortion.
‫ووصار‬In position of 23°adbuction
‫تقريبا برلل حق االكسس اوف أي بول ومافي انقل‬
the only action is ‫لها حركه وحده‬
depression. (optimal position for
function testing).
In position of 67 ° adduction the
only action is extortion. (the line
of pull of the muscle makes 90
degree with the optical axis).
Action of right IR
The oblique muscles
The obliques are inserted behind
the equator, and form angle of
51° with the optical axis.
Orbital
axis
Axis of
vertical
recti
Optical
axis in
primary
position
Axis of
oblique
recti
The superior oblique
Originates above and medial to optic
canal, passes through the trochlea
between the superior and medial orbital
walls, become reflected backwards, to
insert in the posterior upper temporal
quadrant of the glob.
Insertion of the oblique muscles
in the sclera posterior to the
equator (right Eye).
Superior
oblique:
upper post.
Lateral
part.
Inferior
oblique:
lower post.
Lateral part
Its primary action in the
primary position is
intortion, its secondary
actions are depression
and abduction.
In position of 51°
adduction, its only
action is depression.
(0ptimal position for
testing of function).
In position of 39°
abduction its only
action is intortion. (the
line of pull of the
muscle makes 90° with
the optical axis).
Action of SO
The inferior oblique
Originates from small depression just
behind the lower orbital margin, lateral
to the tear duct, to insert in the
posterior lower temporal quadrant of
the glob. (close to the macula).
Its primary action in the
primary position is
extortion, its secondary
actions are elevation
and abduction.
In position of 51°
adduction, its only
action is elevation.
(0ptimal position for
testing of function).
In position of 39°
abduction its only
action is extortion. (the
line of pull of the
muscle makes 90° with
the optical axis).
Action of IO
Remember,
The 0bliques are abductors
and verticals are adductors.
The superiors are intortors,
and the inferiors are
extortors.
The eye ball
• Surrounded by fascial
sheath (tenon capsule)
• Formed of segments of 2
spheres; ant transparent
smaller and post opaque
larger.
• Ant. Pole is the center of
curvature of ant. Segment,
post. pole is the center of
curvature of post. Segment.
The equator lies midway
between the two poles.
The coats and contents of the eye ball
A- Coats
1- The outer protective
(fibrous):
cornea (clear) and sclera
(junction is the limbus). ‫بين‬
‫السكليرا والكورنيا‬
2- The middle vascular layer:
Iris, ciliary body and
choroid.
3- The inner nervous layer:
Retina.
The coats and contents of the eye ball
B- contents:
- Anterior chamber
between cornea and iris
( have hol in middel >>
pupil ) , filled with
aqueous.
- Crystalline lens ‫ورى‬
‫البيوبل‬
- Posterior chamber
between iris and lens,
filled with aqueous
-The
cavity
filled with the vitreous
fromvitreous
cillary body
.
body
‫ الي الضووؤء يمر خاللها لين يوصل الريتنا‬Refractive media of th
Cornea, aqueous, the lens and the vitreous body.
The cornea
• Transparent anterior 1/6 of the outer
coat 70% of refrection of eye {{
major part in refraction and it fixed
• Diameter: about 12 mm.
• Thickness: central 0.56mm
peripheral 1mm.
• Refractive power: 42 D (75% of the
Histologically:
formed of 5 layers.
1- Epithelium (Stratified
nonkeratinized squamous epith).
2- Bowman’s membrane.
3- stroma. (( main
thikmness )
4- Descemet’s membrane.
5- Endothelium.
The limbus is the
corneoscleral junction
The cornea
• Nerve supply: very reach in sensory
supply from nasociliary branch of
trigeminal nerve (5th) cranial nerve
(sensory).
• It is avascular, nutrition through limbal
capillaries, aqueous humor, and tear
film caver the cornea
Tear film
The cornea: is the part with
main refractive power in the
eye.
Factors responsible for
corneal Transparency:
• Avascular >> in ifnlamation will be opay
• Regular stromal lamellae << if irregular will be
opay
• Endothelial pump: removal of excess fluid by
the endothelium>> any difunction >> edema >>
opay
• Non-myelination of corneal nerves >> will be
mailenated in liprosy for example
Sclera
• Posterior 5/6 of the outer coat
• White in color ,may be bluish in
children
• Thickness: 1 mm posterior, 0.6 mm
at equator 0.3 mm at insertion of
recti muscles (thinnest area).
‫ الزم كل‬Scleral foramina
‫الستركجر تروح حق السكليرا‬
• Anterior : exit of
anterior ciliary vessels
and nerves
( at the insertion of
the recti)
• Equatorial: exit of
vortex veins
• Lamina cribrosa: exit
of optic nerve bundles
• Posterior: around optic nerve:
exit of posterior ciliary vessels
and nerves
Sclera , structure, function
• Episclera.
• sclera is separated from choroid by
suprachoroidal space.
• Thick collagenous bundles running in
various directions.
- Functions:
• Protection
• Insertion of muscles
• Preserve shape of globe
Vascular layer
• Iris
• Ciliary body
• Choroid
The Iris
• Pigmented contractile diaphragm with
central opening called the pupil.
-Iris pattern is the presence
of fine irregularities on
the anterior iris surface
due to presence of the
collarette (irregular
circular line) and the
crypts (areas of dark
depressions).
-It is divided by the
collarets into pupillary
and cilliary zones.
-The post. Surface is darkly
pigmented.
-The iris is attached to the
middle of the antrior
surface of the cilliary
body.
Iris structure
• Iris stroma contains two muscles;
sphincter pupilae ( ‫كونستركتر ببلري مصل‬
supplied by oculomotor (3rd) nerve
(parasympathetic) and dilator
pupillae supplied by sympathetic
system.
• Iris epithelium: two layers on the back surface
of the iris rich in melanin
Iris function
• Control amount of light entering the
globe through the action of sphincter
and dilator pupillae
• Give the color of the eye through the
melanin pigment
The Ciliary body
It extends between the
iris and choroid.
It is triangular in cross
section.
The base of the triangle
(anterior surface) is
continuous with the iris
root.
The apex is directed
posteriorly and is
continuous with the
choroid.
The Ciliary body
The anterior surface (base)
is called pars plicata
and it contains 60-70
process and gives
attachment to the lens
zonules and responsible
for aqueous formation.
The posterior surface is
smooth and is called
pars plana (important
surgical land mark) ‫عشان‬
‫نوصل الفترس بدون ما نسوي‬
‫انجوري حق اللنس او الريتنا‬. It
lies against the sclera.
Histologically:
Formed of ciliary epithelium, stroma, ciliary
muscles.
-ciliary muscles: 3 parts;
1- longitudinal fiber.
2- circular fibers.
3- oblique fibers.
Nerve supply parasympathetic from occulomootr
(3rd) nerve.
Functions of ciliary body
• Accommodation.
• Formation of the aqueous humor. >> to
control inra ocular prassure
Anterior chamber angle
• Between cornea
and iris
• It is the main pathway for
drainage of the aqueous.
Contents:
•
•
•
•
•
Rote of iris
Ciliary band
Scleral spur
Trabecular meshwork
Schwalbe’s line
The choroid
• Highly vascualr and pigmented
membrane between the sclera and
retina
• Formed of large, medium sized and
small vessels and choriocapillaris.
• Main function is to nourish the
retina
A- long
post.
Ciliarry
arteries.
C- short
post.
Ciliarry
arteries
D- anterior
cilliarry
arteries
K- vortex
veins
The crystalline lens
• It is a transparent, biconvex
structure lies behind the iris
and in front of the vitreous
body.
• The convexity of its ant.
Surface is less than of its
posterior surface.
• 4 mm thick 10 mm diameter
• It is kept in place by the
suspensory ligaments.
• Center of ant.s called
antirior pole .. And the post.
The same ‫اسمه بوستيريور بول‬
• The priphri of lens called
equator
• The lens is formed of:
1- lens capsule, elastic clear membrane. {{ caver the
lens
2- Subcapsular epithelium, single layer of cells under
the anterior capsule and absent at posterior
capsule. At the equator it become transferred to
lens fibers.
3- lens fibers. The earliest fibers moves centrally and
form the nucleus , and the later fibers form the
cortex.
With advancing of age
(about 25 years of age),
the nucleus becomes
progressively harder in
component.
‫بره كبسول في النص كورتكس‬
• The lens is avascular and nutrition
is obtained by diffusion from
aqueous.
• Functions of the lens:
1- refractive media (25% of the
refractive power of the eye).
2- protects retina from ultraviolet
rays.
3- accommodation >> main
Accommodation:
It is the ability of the lens to increase its
refractive power so that images of near
objects can come to focus on the retina.
(it is part of the near reflex).
Mechanism: contraction of the circular fibers of ciliary muscle causes
relaxation of the lens zonules and the lens becomes more spherical
mainly at its anterior surface and its refractive power increases.
The Vitreous Body
• It fills the posterior
cavity of the eye
between the lens and
retina.
• It is clear transparent
semi-fluid, and
avascualr.
• Loosely adherent to the
retina except around
the optic disc, the
major retinal vessels
(both gets weaker with
ageing) and at the
extreme periphery
;vitreous base (never
gets weaker with
ageing). Sport to ball
The
anterior surface is
adherent to the lens by the
hyaloido-capsular
ligament. It becomes
weaker with aging.
The Retina
• It is the inner
most sensitive
(nervous) layer
of the eye.
• It extends from
the ciliary body
to the optic
disc.
• transparent
showing the
red color of the
underling
chororidal
vessels.
Retina, Left Eye
The retina
• Orra serrata: junction of retina to
ciliary body
• Macula: central part of the retina,
contain xanthophil pigment
• Optic disc: exit of nerve fibers to
higher visual centers
the macula lutea:
The fovea is a central
depression formed
by displacement of
layers of the retina
leaving the
photoreceptors with
highest
concentration of
cones. Its avascualr.
The center of the
depression is called
the foveola. ‫اهم منطقه‬
‫حق الفجن والكلور فجن النها‬
‫فيها واجد كونز سل فاهي‬
Structure:
formed of 10 layers
1-the Retinal
pigment
epithelium.
2-rods and cones.
3-external limiting
membrane.
4-outer nuclear
layer.
5-outer plexiform
layer.
6-inner nuclear
layer.
7-inner plexiform
layer.
8-Gangelion cells.
9-nerve fiber layer.
10-internal limiting
membrane.
Physiology of vision
When light falls on the retina the following
occurs:
1- The rhodopsin in the rods (responsible for
night vision) is broken down (to retinene and
Vit. A) and gives rise to electrical changes.
This process is reversed in the dark. The cone
pigment (responsible for color and day vision)
has the same response but to specific wave
length of light giving the sense of color.
2- this electrical changes passes through the
visual pathway to the brain to produce visual
sensation.
The Retina : Anatomy
The blood supply of the retina :
The outer lamina : ( RPE, Rods, Cones , and outer nuclear layer)
Supplied by the choroidal capillaries
The Retina : Anatomy
The blood supply of the retina :
The inner lamina : (The rest of the retinal layers)
Supplied by the central retinal artery&vein .
The Optic Nerve
- Is made of all ganglion cells axons that
becomes myelinated behind lamina cribrosa
(scleral foramina that gives passage to the
nerve).
- It runs through lamina cribrosa leaves the orbit
through the optic canal to reach the optic
chiasma.
- Its surrounded by dense sheath of dura mater,
middle delicate sheath of arachnoid, and inner
most vascular pial sheath. ‫النقطه الفاتحه الي نشووفهاا‬
‫من البيوبل اهي بدايه االوبتك نيرف‬
the optic disc:
-Nasal to the
macula.
-1,5 mm in
diameter.
-Pale pink in color.
-rounded in shape,
Well-defined edges.
-central physiological cup ‫مافيه نررف مار في‬
‫الوسط‬, Lamina cribrosa is seen.
- Central retinal vessels enter and leave the
eye from the cup.
The visual pathway
Made of:
- optic nerve.
- optic chiasma
(crossing of nasal
fibers occurs).
- optic tracts.
- lateral geniculate
bodies.
- optic radiations.
- visual cortical areas
(17-18)
The visual nerve pathway
• Sensory end organs: Rods and cones.
• The first order neuron: bipolar cells of
retina.
• The second order neuron: Ganglion cells
of retina.
• Third order neuron: cells of the lateral
geniculate body.