10 - The Orbit 2 - Shorooq's Part

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					The Orbit
Bones forming the orbit are:
         1- Frontal
         2- Ethmoid
         3- Palatine
         4- Zygomatic
         5- Lacrimal
         6- Maxilla
         7- Sphenoid


Orbital Margins are :
         1. Superior margin; frontal bone
         2. Inferior margin; maxilla and zygomatic
         3. Medial margin; frontal, lacrimal and maxilla
         4. Lateral margin; zygomatic and frontal
The orbital cavity contains walls:
The Roof formed by the frontal and sphenoid
The Lateral Wall; zygomatic & sphenoid
The Floor; maxilla, zygomatic & palatine
The Medial Wall; maxilla, lacrimal, ethmoid &
sphenoid


Five orbital openings :
Optic Foramen (C.N II & ophthalmic artery)
Superior Orbital Fissure (C.N III, C.N IV, C.N
VI, ophthalmic vein & sympathetic fibers)
Inferior Orbital Fissure (Maxillary nerve,
infraorbital vessels and ascending branches
from sphenopalatine ganglion)
Supraorbital Foramen (supraorbital nerve,
supraorbital vessels)
Lacrimal Fossa :
Indicates one of two (fossa of lacrimal gland, or
fossa of lacremal sac in the pic.)
Contents of the Orbit :
Eyeball
Extraocular Muscles
Nerves (C.N II, III, IV, V, VI)
Blood Vessels
Extraocular Fat
Lacrimal gland, Lacrimal sac, Nasolacrimal duct
Eyelids
Ligaments
Conjunctiva
Trochlea
Orbital Septum
Ciliary ganglion

Extra-ocular muscles and their movements:
Levator palpebrae superioris: innervated by the
oculomotor nerve and smooth muscle fibers are
innervated by sup. Cervical Sympathetic ganglion
The recti:
     superior rectus -superior when the eye is
     abducted
     medial rectus- medially
     inferior rectus-inferior , the eye is abducted
     lateral rectus-laterally
Superior oblique-inferior when the eye is adducted
Inferior oblique-superior ,the eye is adducted
Orbital Septum: It is a membranous sheet that acts as the anterior boundary of the
orbit.

It is attached to the orbital margin where it is continuous with the periosteum, and
then it goes through the eyelid as a sheet that thickens at the margin of the lid to
form the tarsal plate.

The tarsal plate contains the tarsal gland which is a sebaceous gland in the eyelid.




         Orbital septum




                                      Orbital septum
   Review slid !




Name each of the numbered bones.
Which bone is thinnest?
Which is most likely to fracture after
blunt injury?
Which is most likely to erode from
sinus infections?

The bones are: (1)Sphenoid (2)Zygomatic (3)Maxilla (4)Lacrimal (5)Ethmoid
(6)Frontal. The ethmoid is the thinnest bone and most likely to perforate from
an eroding sinus infection (this happens mostly in kids). The maxillary floor
is most likely to fracture from blunt injury.
What is the function of the Orbit ?

The orbit holds the eye in the correct position.


The three basic structures that determine globe position of the eye are the bony
   orbits, the ligament and muscle system & the orbital fat.

The orbit also protects the eye because the bones surrounding the eye “stick out”
   further than the eye, objects tend to hit the orbit and not the eye.

Transmits nerves and blood vessels.
Clinical features of orbit diseases:
    Despite the number of different tissues present in the orbit, the
     expression of disease due to different pathologies is often similar.


    Clinical features are:
1.   Exophthalmos (proptosis)
2.   Enophthalmos
3.   Pain
4.   Eyelid and conjunctival changes
5.   Diplopia
6.   Visual acuity disturbances
  It is a protrusion of the eyeball.
  could be unilateral or bilateral.




Bilateral proptosis                    Unilateral proptosis
Causes :
   Causes are classified into:

     1.   Intra-conal lesions: the lesion lies
          within the cone formed by extra-
          ocular muscles, thus the eye globe
          is displaced directly forwards, e.g.
          most commonly dysthyroid eye
          disease, others like Optic nerve
          sheath meningioma.

     2.   Extra-conal lesions: the lesion is
          outside the cone, so the eye is
          displaced to one side, e.g. mostly
          tumors, tumor of the lacrimal
          gland displaces the globe nasally.
Examples :
   The most common cause is Graves
    disease, it usually causes bilateral
    proptosis.
   Infectious (Orbital cellulitis)
   Orbital Inflammatory disease
   Vasculitis (wegener’s granulomatosis)
   Neoplastic (unilateral): Lacrimal,
    Lymphoma, Metastatic.
   Orbital vascular disease (orbital
    varices...causes transient proptosis on
    valsalva manouver)
   Trauma
   Pseudoproptosis
    (pseudoexophthalmos)
     o Buphthalmos ( congenital open
         angle glaucoma)
     o Contralateral enophthalmos
     o Ipsilateral lid retraction
Approach to Exophthalmos:
        History:
           duration, rate of onset.
           associated ocular symptoms (pain, decreased visual acuity or field, diplopia,
             transient visual loss).
           complaints of foreign body sensation or dry gritty eyes
           history of trauma
           family history
Onset:
   Slow onset usually indicates benign tumors.
   Fast onset indicates inflammatory disorder
         malignant tumors, caroticocavernous sinus fistula.
   intermittent onset indicates orbital varices,induced by
   increasing the cephalic (head) venous pressure.
        Examination:
           Full ophthalmic & systemic examination
           Exophthalmometer

        Treatment :depends on the underlying cause, but if left untreated it could lead to:
           1. Failure of the eyelids to close, causing corneal ulcerations and damage.
           2. Compression on the optic nerve or ophthalmic artery leading to blindness
The amount of ocular protrusion measured (with
Hertel Exophthalmometer) from the lateral orbital rim
(zygomatic bone) to the corneal apex.



 > 21 mm or a 2mm
 difference between
the two eyes is
 abnormal.
Complications
If it is left untreated
it could lead to:

   Failure of the eyelid to close
    leading to corneal damage ,
    ulceration , & Possibly perforation
    .

   Compression on the optic nerve or
    ophthalmic artery leading to
    blindness

   Restriction of eye movements &
    squint …
Definition: Relative recession (backward or
downward displacement) of the globe into the bony
orbit

•Presents clinically as a sunken appearance to the eye
with pseudoptosis.




       The doctor said this is mostly ptosis , sorry !
       U can check slid 17 for a better photo 
CAUSES OF ENOPHTHALMOS:
1.   Primary enophthalmos indicates a
     congenital etiology( Postnatal,
     inadequate, orbital cavity
     development)

2.   Acquired ( secondary):
-    * Blow out trauma
-    * Postsurgical muscle shortening

-    Horner’s Syndrome .. Will cause
     aberrant enophthalmos ; due to
     ptosis !!!
Treatment : involves reconstruction of the bony
orbit with restoration of bony orbital volume and
repositioning of the globe.




Complications : Long-standing enophthalmos,
especially associated with very extensive orbital
trauma, may be associated with severe orbital
scarring, and correction can be very difficult or
impossible.
Investigation of orbital disease

1.     CT
2.     MRI
3.     Systemic tests
       depending on the
       DDx.

Fun fact !
An ostrich’s eye is larger than
its brain ! 
Differential diagnosis of orbital
diseases
       Trauma
       Disorders of extra-ocular
        muscles (Dysthyroid eye
        disease and ocular myositis,
        rhabdomyosacroma)
       Infective disorders (orbital
        cellulitis and preseptal
        cellulitis)
       Inflammatory diseases
        (Sarcoidosis, orbital pseudo-
        tumors caused by
        lymphofibroblastic disorders)
       Vascular abnormalities
        (Carotico-Cavernous sinus
        fistula, orbital varix, capillary
        hemangioma)
       Orbital tumors (lacrimal
        gland tumors, meningioma of
        the optic nerve, optic nerve
        glioma, rhabdomyosarcoma)
       Dermoid cysts
Thank you

by Shorooq Abdoh
You can’t depend on your eyes when your
imagination is out
of focus.

Mark Twain

				
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posted:8/16/2012
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