3. The Orbit & The Eye very jvaosnfsd.pdf

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1. ANATOMY III
3. The Orbit & The Eye
DR. MOHAMAD BAKER ABU-SNAINA
GENERAL SURGEON

2. The Orbit
•A pair of bony cavities that open in the
face, guarded by the eyelids.
•It is pyramidal in shape, having a base,
an apex & 4 walls.
The base, opens in the face as the
orbital opening, has 4 margins:
Superior: the frontal bone.
Inferior: the maxilla (medially) & the
zygomatic bone (laterally).
Medial: maxillary process of frontal
bone & frontal process of maxilla.
Lateral: zygomatic process of frontal &
frontal process of zygomatic bones.

3. The Orbit
The apex: corresponds the optic canal
The roof:
The orbital plate of frontal bone,
(anteriorly) the main part which
separates the orbital cavity from
anterior cranial fossa & frontal lobe.
Lesser wing of sphenoid bone (post.)
The floor:
The orbital plate of maxilla, separates
the orbit from maxillary sinus.
Maxillary process of the zygoma.
Orbital process of palatine bone.

4. Medial wall:
The frontal process of maxilla.
Lacrimal bone
Body of sphenoid.
The orbital plate of ethmoid
(separates the orbit from
ethmoid sinuses).
Lateral wall:
Frontal process of zygomatic
bone.
greater wing of sphenoid.
The Orbit

5. Openings Into the Orbital Cavity
•Orbital opening: Lies anteriorly,
guarded by two thin, movable
folds, the eyelids.
•Supraorbital notch lies on the
superior margin & transmits the
supraorbital nerve & blood
vessels.
•Infraorbital groove & canal:
situated on the floor of the orbit
in the orbital plate of the
maxilla; transmit the infraorbital
nerve & blood vessels.

6. •Nasolacrimal canal: lies
anteriorly on the medial wall; it
communicates with the inferior
meatus of the nose, It transmits
the nasolacrimal duct.
•Inferior orbital fissure: Located
posteriorly between the maxilla
& greater wing of sphenoid,
transmits the maxillary nerve &
its zygomatic branch, the inferior
ophthalmic vein & sympathetic
nerves.
Openings Into the Orbital Cavity

7. •Superior orbital fissure: lies
posteriorly between the
greater & lesser wings of
sphenoid, transmits the
lacrimal, frontal, trochlear,
oculomotor, abducent &
nasociliary nerves & superior
ophthalmic vein.
•Optic canal: lies posteriorly in
the lesser wing of the
sphenoid, It transmits the
optic nerve & the ophthalmic
artery.
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Openings Into the Orbital Cavity

8. 8

9. Eyelids
•The upper eyelid is larger & more
mobile than the lower & they meet
each other at medial & lateral angles.
•The palpebral fissure is elliptical
opening between the eyelids.
•When the eye is open & looking
straight, the upper lid just covers the
upper margin of the cornea.
•The lower lid lies just below the
cornea when the eye is open & rises
only slightly when the eye is closed.
•The free margin of each eyelid
possesses 2-3 rows of eyelashes at the
mucocutaneous junction.
Protect the eye

10. Skin: thin, loose, no subcutaneous fat,
easily distensible by edema/blood
Muscular layer: contains the palpebral
part of the orbicularis oculi (in both
upper & lower eyelids), in addition the
levator palpebrae superioris muscles in
the upper eyelid.
Tarsus: a plate of dens fibrous tissue.
•Tarsal glands are embedded in the tarsi
& their ducts open behind eyelashes.
•Both tarsi are attached to the medial &
lateral orbital margins by medial&
lateral palpebral ligaments.
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Structure of Eyelids

11. Structure of Eyelids
Conjunctiva: (palpebral Conjunctiva)
•It is the mucus membrane that lines
the inner surface of each eyelid.
•It is reflected on the sclera.
Arteries of the eyelids:
Medial palpebral artery from
ophthalmic artery.
Lateral palpebral artery from
ophthalmic artery.
Nerves of the eyelids:
Upper eyelid: by ophthalmic nerve.
Lower eyelid: by maxillary nerve.

12. Movements of the Eyelids
•The position of the eyelids at rest depends on tone of the
orbicularis oculi & the levator palpebrae superioris
muscles & the position of the eyeball.
•The eyelids are closed by contraction of orbicularis oculi
& relaxation of levator palpebrae superioris .
•The eye is opened by the levator palpebrae superioris
raising the upper lid.
•On looking upward, the levator palpebrae superioris
contracts & the upper lid moves with the eyeball.
•On looking downward, both lids move, the upper lid
continues to cover the upper part of the cornea, & the
lower lid is pulled downward slightly by the conjunctiva,
which is attached to sclera & lower lid.

13. The Orbit contains:
•Eyeballs, orbital fate, ligaments &
fascia.
•Extra-ocular muscles.
•The lacrimal apparatus.
•Vessels: ophthalmic artery & vein.
•Nerves:
Optic nerve : for vision.
Ophthalmic nerve : for general sensation.
Oculomotor, trochlear &abducent
nerves: motor to the muscles of the eye.
Ciliary ganglion, parasympathetic.
Sympathetic fibers from sup. cervical gan

14. Lacrimal Apparatus
The lacrimal gland consists of:
Large orbital part: lies in the lacrimal
fossa in the anterolateral part of the
roof of the orbit, above the eyeball.
Small palpebral part: embedded in
the lateral part of the upper eyelid.
The 2 parts are continuous together
around the lateral margin of the
levator muscle.
•The gland opens into the lateral part
of the superior fornix of the
conjunctiva by 12 ducts.

15. •The parasympathetic secretomotor
nerve supply is derived from the
lacrimal nucleus of facial nerve.
•The sympathetic postganglionic
supply is from internal carotid
plexus
lacrimal sac: lies in the lacrimal
groove present in the anterior part
of the medial wall of the orbit.
•It is the upper blind end of the
nasolacrimal duct, present in the
nasolacrimal canal.
Lacrimal Apparatus

16. Lacrimal Apparatus
Lacrimal puncti, canaliculi:
•The lacrimal puncti are 2
minute opening in the medial
end of the margins of the
upper & lower eyelids, these
puncti lead to the lacrimal
canaliculi.
•Lacrimal canaliculi: each
canaliculus runs in the edge of
the corresponding eyelid for a
short distance to join the
lacrimal sac.

17. Nasolacrimal duct is about 0.5
inch long & emerges from the
lower end of lacrimal sac,
descend downward, backward, &
laterally in bony canal & opens
into the inferior meatus of nose.
•The opening is guarded by a fold
of mucous membrane known as
the lacrimal fold.
•This prevents air from being
forced up the duct into the
lacrimal sac on blowing the nose.
Lacrimal Apparatus

18. The eyeball
•The eyeball is embedded in orbital fat but separated from
it by the fascial sheath of the eyeball.
The eyeball consists of 3 coats, from without inward:
The fibrous coat: Sclera & Cornea.
The vascular pigmented coat: Choroid, Ciliary body & Iris.
The nervous coat: Retina.
The cavity of the eyeball consist of the refractive media:
The aqueous humor.
The vitreous body.
The lens.

19. Fascial Sheath of the Eyeball
•The fascial sheath surrounds
the eyeball from the optic
nerve to the corneoscleral
junction.
•It separates the eyeball from
the orbital fat & provides it
with a socket for free
movement.
•It is perforated by the tendons
of the orbital muscles.
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20. The Sclera
•It is the posterior part of the
outer coat, composed of dense
fibrous tissue, white & opaque.
•Posteriorly, it is pierced by the
optic nerve at the lamina cribrosa
& fused with the dural sheath of
that nerve.
•It is also pierced by the ciliary
arteries & nerves & their veins.
•It is directly continuous in front
with the cornea at the
corneoscleral junction, or limbus.

21. The Cornea
•It is the transparent anterior part of
the outer coat.
•It is avascular & devoid of lymphatic
drainage, nourished by diffusion
from the aqueous humor with which
it is in contact posteriorly.
•Nerve supply by long ciliary nerves
from the ophthalmic division of
trigeminal nerve.
•It is the most important refractive
medium of the eye.
•Tear film in maintains the normal
environment for corneal epithelium.

22. The Choroid
•The choroid is composed
of:
Outer pigmented layer.
Inner highly vascular layer.

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23. The Ciliary Body
•The ciliary body is continuous:-
Posteriorly with the choroid.
Anteriorly: lies behind the
peripheral margin of the iris.
•It is composed of: the ciliary
ring, the ciliary processes & the
ciliary muscle.
The ciliary ring: is the posterior
part of the body, shows radially
arranged ridges.

24. 24
The Ciliary Body
The ciliary processes: each process
is attached to the ciliary ring on
one hand & to the periphery of the
iris & suspensory ligament of the
lens on the other hand.
The ciliary muscle: unstriated
muscle consists of 2 parts:
oMeridional direction fibers: extend
from the sclera to the ciliary
process
oCircular direction fibers: deep to
the meridional fibers.

25. •Nerve supply of ciliary muscle is
the parasympathetic fibers from
the oculomotor nerve.
•Action: it is the main muscle of
accomodation.
•Contraction of the ciliary muscle
pulls the ciliary body forward,
this relieves the tension in the
suspensory ligament & the lens
becomes more convex.
•This increases the refractive
power of the lens.


The Ciliary Body

26. The Iris & Pupil
•It is a thin, contractile, pigmented
diaphragm with a central aperture,
the pupil.
•It is suspended in the aqueous
humor between the cornea & lens
divides this space into anterior
chamber & posterior chamber.
•Its periphery is attached to the
anterior surface of the ciliary body.
•It contains involuntary muscle fibers:
Circular fibers.
Radiating fibers.

27. The circular fibers forms the sphincter
pupillae, arranged around the margin of
the pupil, supplied by parasympathetic
fibers from the oculomotor nerve.
•It constricts the pupil in the presence of
bright light & during accommodation.
The radial fibers form the dilator
pupillae lie close to the posterior
surface, is supplied by sympathetic fibers
•It dilates the pupil in the presence of low
light intensity or in the presence of
excessive sympathetic activity such as
occurs in fright.

The Iris & Pupil

28. The Retina
•It consists of an outer pigmented
layer & an inner nervous layer.
•Its outer surface is in contact
with the choroid & its inner
surface is in contact with the
vitreous body.
•The posterior ¾ of the retina is
the receptor organ(rods &
cones).
•The anterior part is nonreceptive
& consists of pigment cells.

29. The Retina
•The optic disc: is a rounded area 1.5
mm in diameter , consists only of
optic nerve fibers, pierced by the
central artery of the retina, with no
receptors, so it is insensitive to light
(called the blind spot)
•The macula lutea: is an oval,
yellowish area, at the center of the
posterior part of the retina lateral to
the optic disc, contains only cones,
area of the most distinct vision.
•Has a central depression, the fovea
centralis.

30. Aqueous Humor
•It is a watery fluid fills the anterior &
posterior chambers of the eyeball.
•It is secreted from vessels of the iris
& ciliary body, enters the posterior
chamber, then flows into the
anterior chamber through the pupil
& is drained away through the
spaces at the iridocorneal angle into
the canal of Schlemm.
•Obstruction to the draining of the
aqueous humor results in a rise in
intraocular pressure called
glaucoma.

31. Vitreous Body
•It is a transparent jelly-like
substance that fills the eyeball
behind the lens.
•It is enveloped by the hyaloid
membrane.
•It supports the posterior surface
of the lens & assists in holding
the neural part of the retina
against the pigmented part of the
retina.
•contribute slightly to the
magnifying power of the eye.

32. The Lens
•It is a transparent, biconvex
structure.
•Situated behind the iris & in front
of the vitreous body.
•Enclosed in a transparent capsule
which gives attachment to the
suspensory ligament encircled by
the ciliary processes.
•This ligament is a part of the haloid
membrane ensheathing the
vitreous body & it keeps the lens in
place.

33. •The elastic lens capsule is under
tension, causing the lens constantly
to assume a globular rather than a
disc shape.
•The circumference, of the lens is
attached to the ciliary processes of
the ciliary body by the suspensory
ligament.
•The pull of the radiating fibers of
the suspensory ligament tends to
keep the lens flattened so the eye
can be focused on distant objects.

The Lens

34. The Extraocular Muscles
•These are the six muscles that control
the eye movement & one muscle that
controls eyelid elevation (levator palp.)
•The action of the 6 muscles
responsible for the eye movements
depend on the position of the eye at
time of muscle contraction.
•4 recti muscles: superior rectus,
inferior rectus, medial rectus & lateral
rectus.
•2 oblique muscles: superior oblique &
inferior oblique.
•Levator palpebrae superioris.

35. The 4 recti muscles
•Common origin: tendinous ring
on posterior wall of orbital
cavity.
•Insertion: each muscle passes
straight forward to be inserted
into the sclera just posterior to
corneoscleral junction.
They are arranged as follows in
relation to the eyeball:
The superior rectus (above),
inferior rectus (below), medial
rectus (medial), lateral rectus
(lateral).

36. Superior oblique
Origin: posterior part of the
roof of the orbit above & medial
to the optic foramen.
Insertion: it runs forward above
the medial rectus, then its
tendon passes through the
trochlea then curves backwards,
downwards & laterally to be
inserted into the sclera between
the superior rectus & lateral
rectus.

37. Inferior oblique
Origin: floor of orbital cavity, just
lateral to the lacrimal groove.
Insertion: the muscle runs
backwards, upwards & laterally
below the eyeball to be inserted into
the lateral aspect of the sclera.
All the extraocular muscles are
supplied by the oculomotor nerve
(CN III), except:
Superior oblique by the trochlear
nerve (CN IV). (SO4)
Lateral rectus by the abducent nerve
(CR VI). (LR6)

39. Intrinsic Muscles of the eye
•The involuntary intrinsic muscles are:
 The ciliary muscle.
 The constrictor & the dilator pupillae of the iris.
•They take no part in the movement of the eyeball.

40. Optic Nerve II
•it is a special sensory nerve carrying
the visual impulse.
•Its fibers are the axon of the ganglion
of the retina.
•It runs within the recti muscles,
passes through the tendinous ring &
leave the orbit through optic canal.
•It ends in the middle cranial fossa by
joining its fellow forming the optic
chiasma.
•It is surrounded by sheaths of the
three meninges.

41. •The nerve is pierced by the central
artery of the retina (branch of the
ophthalmic artery).
•Pierces the sclera at a point medial
to the posterior pole of the eyeball,
here, the meninges fuse with the
sclera so that subarachnoid space
extends forward from the middle
cranial fossa, as far as the eyeball.
•A rise in pressure of CSF within the
cranial cavity is transmitted to the
back of the eyeball.
Optic Nerve II

42. Ophthalmic Nerve (V1)
•It is a general sensory nerve,
one of the 3 division of the
trigeminal nerve.
•It runs forward in the lateral
wall of the cavernous sinus,
below the oculomotor &
trochlear nerves & above the
maxillary nerve.
•Leaves the cavernous sinus,
then divided into 3 branches:
lacrimal, frontal & nasociliary all
enters the orbit through the
superior orbital fissure.

43. Nasociliary Nerve
•It crosses above the optic nerve,
runs forward along the upper
margin of the medial rectus
muscle, ends by dividing into:
Anterior ethmoidal.
Infratrochlear nerves.
•Branches:
The communicating branch to
ciliary ganglion.
The long ciliary nerves, 2or3 in
number, contain sympathetic
fibers for the dilator pupillae
muscle.

44. Nasociliary Nerve
Posterior ethmoidal nerve supplies
ethmoidal & sphenoidal air sinuses.
The infratrochlear nerve supplies skin
of the medial part of the upper eyelid
& the adjacent part of the nose.
The anterior ethmoidal nerve passes
through the anterior ethmoidal
foramen & enters the anterior cranial
fossa, then enters the nasal cavity.
Supplies an area of mucous
membrane, it appears on the face as
the external nasal branch at the
lower border of the nasal bone &
supplies the skin of the nose.

45. Lacrimal Nerve
•Passes forward along the upper
border of the lateral rectus
muscle.
•It is joined by a branch of the
zygomaticotemporal nerve,
which later leaves it to enter the
lacrimal gland (parasympathetic
secretomotor fibers).
•The lacrimal nerve ends by
supplying the skin of the lateral
part of the upper lid.

46. Frontal Nerve
•Passes forward on the upper
surface of the levator palpebrae
superioris beneath the roof of
the orbit.
•It divides into:
Supratrochlear.
Supraorbital nerves that wind
around the upper margin of the
orbital cavity to supply the skin
of forehead& mucous
membrane of frontal air sinus

47. Trochlear Nerve IV
•It is the most slender of the cranial
nerves, it is entirely motor.
•Origin: Dorsal aspect of midbrain
•It passes forward through the
middle cranial fossa in the lateral
wall of the cavernous sinus &
enters the orbit through the
superior orbital fissure.
•The trochlear nerve supplies the
superior oblique muscle of the
eyeball (extrinsic muscle), assists
in turning the eye downward &
laterally.

48. Oculomotor Nerve III
•It is entirely motor.
•Origin: anterior surface of
midbrain.
•It passes forward between the
posterior cerebral & superior
cerebellar arteries.
•It then continues into the middle
cranial fossa in the lateral wall of
cavernous sinus.
•Here, it divides into superior &
inferior ramus, which enter the
orbital cavity through the
superior orbital fissure.

49. •The extrinsic muscles of the eye: the levator palpebrae
superioris, superior rectus, medial rectus, inferior
rectus, & inferior oblique.
•The intrinsic muscles of the eye: the constrictor
pupillae of the iris & the ciliary muscles are supplied by
the parasympathetic component of the oculomotor
nerve.
•It is responsible for
Lifting the upper eyelid
Turning the eye upward, downward & medially.
Constricting the pupil.
 Accommodation of the eye.

Oculomotor Nerve III

50. Abducent Nerve VI
•This small nerve emerges from
the anterior surface of the
hindbrain between the pons &
the medulla oblongata.
•It passes forward with the
internal carotid artery through
the cavernous sinus in the middle
cranial fossa & enters the orbit
through the superior orbital
fissure.
•The abducent nerve supplies the
lateral rectus muscle & is
therefore responsible for turning
the eye laterally.

51. Ciliary Ganglion
•It is a parasympathetic ganglion
about the size of a pinhead &
situated in posterior part of orbit.
•It receives its preganglionic
parasympathetic fibers from the
oculomotor nerve via the nerve to
the inferior oblique.
•The postganglionic fibers leave the
ganglion in the short ciliary nerves,
which enter the back of the eyeball
& supply the sphincter pupillae &
the ciliary muscle.

52. Ophthalmic Artery
•It is a branch of the internal
carotid artery after that vessel
emerges from the cavernous
sinus.
•It enters the orbit through the
optic canal with the optic nerve.
•Runs forward & crosses the optic
nerve to reach the medial wall of
the orbit.
•It gives off numerous branches,
which accompany the nerves in
the orbital cavity.

53. Branches of the Ophthalmic Artery
The central artery of the retina is a
small branch, runs in the substance
of the optic nerve & enters the
eyeball at the center of the optic
disc, It divides into branches which
are end arteries.
The Muscular branches.
The ciliary arteries can be divided
into anterior & posterior groups.
The lacrimal artery to lacrimal gland
The supratrochlear & supraorbital
arteries are distributed to the skin of
the forehead.

54. Ophthalmic Veins
•The superior ophthalmic vein
communicates in front with the
facial vein.
•The inferior ophthalmic vein
communicates through the inferior
orbital fissure with the pterygoid
venous plexus.
•Both veins pass backward through
the superior orbital fissure & drain
into the cavernous sinus.
•Note No lymph vessels or nodes are
present in the orbital cavity.