Transcript Embryology And Anatomy Of The Eye And Ocular

Anatomy And Embryology Of
The Eye And Ocular Adnexa
Dr. Abdullah Al-Amri
Ophthalmology Consultant
Contents
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Anatomy of The Bony Orbit
Anatomy of Ocular Adnexa.
Anatomy of The Eye.
Embryology.
Orbital anatomy
• Seven bones make up the bony orbit :
1. Frontal
2. Zygomatic
3. Maxilla (or maxillary bone)
4. Ethmoid (or ethmoidal bone)
5. Sphenoid
6. Lacrimal
7. Palatine
Orbital roof
Medial orbital wall
Orbital floor
Lateral orbital wall
Optic foramen and superior
ophthalmic fissure
Periorbital Sinuses
• The periorbital sinuses have a close
anatomical relationship with the orbits.
• The periorbital sinuses offer a route for the
spread of infection.
• Mucoceles occasionally arise from the sinuses
and can extend into the adjacent orbit.
Extraocular Muscles
• There are 7 extraocular muscles:
1. Medial rectus
2. Lateral rectus
3. Superior rectus
4. Inferior rectus
5. Superior oblique
6. Inferior oblique
7. Levator palpebrae superioris
Origin and insertion
Eye lid
• The palpebral fissure is the exposed zone
between the upper and lower eyelids.
• The upper eyelid is more mobile than the
lower and can be raised I5 mm by the action
of the levator muscle alone.
• The levator muscle is innervated by CN Ill.
Conjunctiva
• The palpebral conjunctiva is a transparent
vascularized membrane covered by a
nonkeratinized epithelium that lines the inner
surface of the eyelids.
• Continuous with the conjunctival fornices it
merges with the bulbar conjunctiva before
terminating at the limbus.
• The conjunctiva
consists of bulbar (red),
forniceal (black), and
palpebral (blue)
portions.
Vascular Supply of the Eyelids
• The blood supply of the eyelids is derived from the
facial system, which arises from the external carotid
artery, and the orbital system, which originates from
the internal carotid artery.
• The venous drainage of the eyelids can be
divided into 2 portions:
1. Superficial system which drains into the
internal and external jugular veins.
2. Deep system which flows into the cavernous
sinus.
Lymphatics of the Eyelids
• Lymphatic vessels are
found in the eyelids and
conjunctiva, but neither
lymphatic vessels nor
nodes are present in
the orbit.
• Swelling of the lymph
nodes is a diagnostic
sign of several external
eye infections.
Lacrimal Gland and Excretory System
• The main lacrimal gland is located in a shallow
depression within the orbital part of the
frontal bone.
• The gland is divided into 2 parts.
• When the upper eyelid is everted, the smaller,
palpebral part can be seen in the superolateral
conjunctival fornix.
Vascular Supply and Drainage of the Orbit
• The posterior ciliary
vessels supply the
whole uveal tract,
the cilioretinal
arteries, the sclera,
the margin of the
cornea, and the
adjacent
conjunctiva.
• The anterior ciliary
arteries supply the
rectus muscles.
• The vortex veins
drain the venous
system of the
choroid, ciliary
body, and iris.
• Venous drainage
of the orbit
occurs through 2
major veins, the
superior and
inferior
ophthalmic veins.
The eye
Cornea and the tear film
The sclera
• The sclera, also known as the white of the eye,
is the opaque, fibrous, protective, outer layer
of the eye containing collagen and elastic
fiber.
• It is of variable thickness, 1 mm around the
optic nerve head and 0.3 mm just posterior to
the muscle insertions.
The uvea
• The uvea is the vascular pigmented middle
layer of the eye.
• It is traditionally divided into three areas, from
front to back:
1. Iris.
2. Ciliary body.
3. Choroid.
The iris
The ciliary body
The retina
The lens
Optic nerve and visual pathway
• This is formed by the axons arising from the
retinal ganglion cell layer.
• In the orbit, the optic nerve is surrounded by a
sheath formed by the dura, arachnoid and pia
mater continuous with that surrounding the
brain.
• The central retinal artery and vein enter the
eye in the center of the optic nerve.
Embryology of the eye
• The eye begins
to develop as a
pair of optic
vesicles on each
side of the
forebrain at the
end of the 4th
week of
pregnancy.
Questions