orbit - anatomy
TRANSCRIPT
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ANATOMY OF ORBIT
Rajvin Samuel Ponraj
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Development of orbit
Develops from mesenchyme by ossification
6 th to 7 th week laying down of bones starting with maxilla bone around theOptic vesicle
During this time optic vesicle 170 degree apart rotates anteriorly
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Developmental Anomalies : Craniosynosotosis:
Brachycephaly
Oxycephaly
Scophocephaly
Trigonocephaly
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Craniosfacial dysostois / Crouzon’ syndrome
Proptosis – shallow orbits
Hypertelorim - wide separation
of orbits
V pattern exotropia
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Oxycephaly-syndactlye / Apert’ syndrome:
Flattened occiput , steep forehead , supra orbital ridge
Midfacial hypoplasia ,parrot beak nose
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Bones of Orbit
Frontal Ethmoid SphenoidLacrimal PalatineMaxillary Zygomatic
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Dimensions - orbit
30 ml –volume 35 mm vertically ,
40 mm horizontally 45 degree between lateral wall
and sagital plane 23 degree between visual
and orbital axis
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Boundaries of Orbit
Roof Floor Side walls Orbital apex
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Roof of orbit Frontal bone [Orbital plate] & lesser wing of sphenoid
Separated from frontal sinus and anteriorcranial fossa above
Lacrimal gland fossa and trochlear fossabehind orbital rim
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Orbital roof anomaly / fracture
CSF pulsation pulsatile
exophthalmos
Orbital meningocele / encephalocele
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Medial wall
Body of sphenoid
Ethmoid
Lacrimal
Maxilla[frontal
process]
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Orbital cellulitis
Extremely thin wall
Prone for damage & sinusitis spread
Infection across Orbital cellulitis
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Floor of orbit
MaxillaZygomaticPalatine
Triangular segment-- thinnestInferior orbital groove
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Blow out fractures
Fragile barrier to maxillary
sinus
Due to trauma eyeball collapse
into Maxillary sinus
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Le fort’s fracture
Type 2 - Pyramidal Type 3 - Craniofacial dissociation
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Lateral wall
Greater wing –sphenoid
Orbital surface –
Frontal process of zygomatic
Inferiorly – inf orbital fissure
Medially – sup orbital fissure
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Behind Zygomatic sphenoidal suture
lateral orbitotomy of greater wing
( thin wall ) cancellous bone
middle cranial fossa
dura matter
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At frontal sphenoidal suture -- meningeal foramen Site of anastomosis of Lacrimal artery and meningeal artery collaterals
Periosteal elevation at this site Brisk bleeding
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Orbital apex
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Orbital apex syndrome
/ Tolosa - hunt syndrome :
Damage to structures at apex 2 nd, 3 rd, 4 th ,6 th nerves
Symptoms : visual loss, ophthalmoplegia
periorbital & facial pain
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Other causes:
a. Inflammatory
b. Infectious
c. Neoplastic
d. Iatrogenic / traumatic
e. Vascular
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Superior orbital fissure syndrome
/ Rochon – Duvigneaud syndrome :
Lesion anterior to orbital apex excluding optic nerve pathology
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Contents of orbit
Eye ball Orbital fat Connective tissue system Blood vessels Nerves Extraocular muscles
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Eyeball - Applied anatomy: Proptosis :
Dystopia
Enophthalmosis
Ophthalmoplegia
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Connective tissue system Periorbita Orbital septum Tenon’s capsule
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Periorbita:
Loosely attached to orbital bone Attached firmly toa. Arcus marginalisb. Trochleac. Lateral orbital tubercled. Optic foramene. Orbital fissuresf. Dura and optic canal margins
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Orbital septum: Interconnecting / circumferential radial
webs of fascial system
support and transmit forces in trauma
Compressive optic neuropathy following trauma
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Anterior fascial system
Formed by condensation of fibrous septa Lockwood lig, whitnall sup susp lig Lacrimal lig Intermuscular septum
Posterior Fascial system Incompletely formed
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Tenon’s capsule
Dense elastic , vascular
Extent : from perilimbal sclera to optic
nerve meninges with bursa within
Sleeve like extensions for
extra ocular muscles continues as
fibrous capsule along its length
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Surgical spaces in orbit : Sub periosteal space Peripheral space Central space Tenon’s space
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Extra ocular muscles
4 rectal muscles 2 oblique muscles Two lid retractors
To serve in eyeball movements in the orbital cavity
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Arterial supply
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Venous drainage
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Optic nerveIntra orbital part = 25 mm out of 4 cm
Enclosed in three meningeal sheaths
At apex surrounded by recti muscles ,Central retinal artery and vein pierces optic nerve 1.25 cm behind optic nerve
Relations: superiorly ophthalmic artery sup ophthal vein nasociliary nerve inferiorly nerve to medial rectus
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Oculomotor nerveDivides at anterior part of cavernous sinus before Entering sup orbital fissure
Sup division Sup rectus LPSInf division Medial rectus Inf rectus Inf oblique
And motor root relay at ciliary ganglion sphincter pupillae , ciliary muscle
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Trochlear nerve
Runs medially from lateral wall of cavernous sinus
Above Levator palpebral supThen supplies orbital surface of Superior oblique
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Abducent nerve
Running inferior lateral to 3 rd nerve then supplies ocular surface of lateral Rectus
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Trigeminal nerve Three terminal branches of ophthalmic division:
I. Frontal nerve supratrochlear supraorbital
I. Lacrimal nerve Sensory and secretomotor fibres to lacrimal gland tru zygomaticotemporal nerve
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Nasociliary nerve:
1. Communicating branch to sensory root of ciliary ganglion
2. Long ciliary nerves - dilator pupillae
3. Posterior and anterior ethmoidal branches
4. Infratrochlear nerve
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