Orbits

Size ,Shape and volume of orbits

General Features

• Volume: 30 mL/cc 

• Shape: Pyramidal. 

Boundaries of orbit

Bony Orbit (7 Bones Total)

• Medial Wall: Composed of (uSMLE)

  • Sphenoid body,

  • Maxillary,

  • Lacrimal, and

  • Ethmoid .

  • It includes the Lamina Papyracea and is the thinnest wall. 

• Inferior Wall / Floor: Composed of (Pa, Ma, Za)

  • Palatine,

  • Maxillary,

  • Zygomatic .

  • It is the weakest point and most susceptible to blunt trauma (blow-out fractures).

• Lateral Wall: Composed of

  • Zygomatic and

  • Greater wing of Sphenoid.

  • It is the thickest and strongest wall.

• Superior Wall / Roof: Composed of

  • Frontal bone

  • Lesser wing of Sphenoid.

Orbital geometry

Orbit Geometry & Axes

• Medial Walls: Parallel to each other, separated by 25 mm

• Lateral Walls: Positioned at 90 degree to each other.

• Orbital Axis vs. Visual Axis: The orbital axis forms a 45 degree angle with the medial wall and a 22.5 degree angle with the visual axis.

Thinnest wall of orbit - _______

Thickest and strongest wall of orbit - _____

Weakest point of orbit /MC part fractured in blunt trauma-_______

1) - Medial wall ( Lamina papiracia)

2) - Lateral wall

3) - Inferior wall / Psteromedial portion

Blow out fracture

• Blow-out Fracture:

  • Caused by blunt trauma to the inferior wall.

  • Features ecchymosis (Panda/Racoon eyes in base of skull fracture),

  • entrapped Inferior Rectus muscle leading to restricted upward gaze,

  • Teardrop Sign on A-P X-ray/NCCT scan.

Which sign on xray seen in fractured blunt trauma to inferior wall?

teardrop sign

Surgical spaces of orbit

surgical Spaces of Orbit

• Subperiosteal Space: Space located beneath the periosteum.

• Intraconal Space: Space inside the muscle cone formed by extraocular muscles.

• Extraconal Space /Peribulbar space: Space outside the muscle cone.

• Sub-Tenon's Space: Space between Tenon's capsule and the sclera.

(Conjunctiva →Tenons capsule →Sclera→ Choroid →Retina)

Anatomy of eyeball

• Layers: 3 coats

  • Outer (Sclera-post.5/6th/Cornea -ant.1/6th),

  • Middle (Uvea: Iris + Ciliary Body + Choroid),

  • Inner (Retina).

• Segments:

  • Anterior Segment:

    • Back of the lens till cornea

    • filled with aqueous humor.

    • Subdivided into the

      • Anterior Chamber - posterior cornea to anterior iris; 2-3 mm

      • Posterior Chamber - posterior iris to anterior lens/zonules).

  • Posterior Segment:

    • From back of the lens to anterior retina surface

    • filled with vitreous humor.

Apex of orbits

• Optic Canal: Traversed by Optic Nerve ({CN II}) and Ophthalmic Artery.

• Superior Orbital Fissure (SOF):

Common tendinious ring divide it in 3 parts =

• Outside Annulus of Zinn:

  • Superior part -

    • Superior Ophthalmic Vein,

    • Lacrimal Nerve, (Branch of CN5)

    • Frontal Nerve, (Branch of CN5)

    • Trochlear Nerve {CN IV}),

    • Recurrent Meningeal Branch of Ophthalmic Artery.

  • Inferior part -

    • Inferior opthalmic vein

• Inside Annulus of Zinn (middle part):

  • Superior & Inferior divisions of Oculomotor Nerve {CN III}),

  • Nasociliary Nerve (CN5),

  • Abducens Nerve {CN VI}.

• Inferior Orbital Fissure (IOF):

  • Infraorbital nerve/vessels,

  • Zygomatic nerve,

  • Inferior ophthalmic veins,

  • Emissary veins.

Extraocular muscles

6 = 4 rectus 2. Oblique

• Suoerior,inferior,medial ,lateral rectus

• Superior , inferior oblique

Nerve Supply - SO4,LR6, rest all 3

Other nerves important supply

1) Lacrimal nerve - Sensory - Periorbital region

2) Frontal nerve - Frontal area

3) Nasocilliary nerve - Afferent - blink reflex

Pathway of blink reflex

afferent -

Subepithelial plexus → Long posterior cilliary nerve → nasocilliafry nerve - 5th cranial nerve 1st division

Efferent pathway -

By facial nerve ( by orbicularis oculi contraction )

Superior orbital fissure syndrome and orbital apex syndrome

Clinical Conditions & Syndromes

Condition	Distinguishing Features	Visual Acuity
Superior Orbital Fissure Syndrome	Proptosis, total external ophthalmoplegia {CN III, IV, VI}), loss of corneal sensation, absent blink reflex.	Normal
Orbital Apex Syndrome	All features of SOF syndrome + Optic Nerve {CN II} involvement.	Decreased / Affected

Orbital cellulitis and preseptal cellulitis

• MC sinus involve - ethmoid sinus

• Mc organism involved - Staph . Aureus

• Preseptal vs. Orbital Cellulitis:

  • Preseptal:

    • Anterior to orbital septum;

    • features periorbital edema without any other symptoms proptosis, vision loss, or limitation of EOM.

  • Orbital:

    • Posterior to orbital septum;

    • proptosis

    • Periorbital edema,

    • Chemosis - swelling of conjunctiva + conjestion

    • dilated non-reacting pupil,

    • painful/restricted EOM, Increase introcular pressure

    • loss of vision ( due to optic nerve involvement )

    • All nerve coming from sup.orbital fissure inflammed,

    • Treatment: IV Vancomycin + 3rd Gen Cephalosporin.

    • Most deadly complication is Cavernous Sinus Thrombosis (earliest sign: Abduction defect due to {CN VI} palsy).

      • Symptoms of complication -

        • Disorientation

        • Slurred speech

        • Cork screw vessels on conjunctiva

        • Ataxia

        • Coma

      • Treatment - IV TPA / LMW heparin

Subperiosteal abscess

• Periosteal abscess = Elevation of periosteum + fluid level

• Fluid level in ethmoid sinus

• Can lead to orbital cellulitis

Tolossa hunt syndrome

• Non specific granulomatous inflammation

• Same symptoms as SOF syndrome / OA syndrome

• Treatment - oral /syestemic steroids

Thyroid eye disease

• Thyroid Eye Disease (TED):

  • Most common cause of both unilateral and bilateral proptosis.

  • Autoimmune disease of thyroid(graves) affects → orbital fibroblasts and extraocular muscles (because same antigen of thyroid as on eye belly)

  • Thyroxine level can be increased,decreased or normal becausewhen first antibodies attack → release all thyroxine → hyperthyroid, after some time → euthyroid, late presentation → Hypothyroidism

  • (order of involvement: I'm So LCKY → Inferior Rectus > Medial Rectus > Superior Rectus > Lateral Rectus).

  • Earliest feature of thyroid eye disease - Dalrymple sign

    • Key Signs:

      • Dalrymple sign (Upper lid retraction via Muller's muscle),

      • Von Graefe sign (Lid lag on downgaze),

      • Stellwag sign (Infrequent blinking),

      • Mobius sign (Convergence insufficiency),

      • Kocher sign (Staring appearance).

      • Goldzeither sign -Conjunctival conjestion

      • Enroth sign - Chemosis

    • Diagnosis/Management:

      • Forced Duction Test -Hold right superior limbus conjunctiva→ eyeball moves up then superior orbital paralysis → if eyeball not moving → inferior rectus fibrosis seen in thyroid eye disease.

    • Treatment

      • involves steroids (1st line), Tocilizumab (2nd line), or surgical sequence: Decompression → Squint Surgery → Lid Correction.

Exophthalmos

Proptosis In thyroid eye disease

Clinical Tests & Observations

• Naffziger's Test:

  • Performed by viewing the patient eye from the behind while he loos up. ("If view from front then → worm's eye view").

  • Qualitative test.

Exophthalmometer Diagnostics

• Exaphthalmometer

• Diagnostic Criteria (Absolute): Proptosis >_ 21mm

• Diagnostic Criteria (Difference): Difference between the two eyes >_3mm

• Hertel's Exophthalmometer: Used to assess exophthalmos in adults.

• Luedde's Exophthalmometer: Used to assess exophthalmos in children.

• Naugle's Exophthalmometer: Used for non-axial proptosis (eye protruding in other directions).

Werner's Classification (NO SPECS Mnemonic)

• N: No signs/symptoms.

• O: Only signs.

• S: Soft tissue involvement.

• P: Proptosis.

• E: Extraocular muscles.

• C: Corneal involvement.

• S: Sight threatening →“ compression of optic nerve.

Management of Thyroid Eye Disease (TED)

• 1st Line Treatment: Steroids.

• 2nd Line Treatment: Tocilizumab.

• 3rd Line Options: Radiotherapy & Surgery.

• Radiotherapy Goal: Decreases inflammation (\downarrow Inflammation).

• Surgical Sequence (TED- D/S/L):

  • D: Decompression

  • S: Squint

  • L: Lid correction

Proptosis

Proptosis Classifications & Intraorbital Tumors

• Axial Proptosis:

  • Eyeball moves centrally forward

  • Optic nerve glioma (glioma MC seen in Neurofibromatis type 1 with IMS-Lisch nodules),

  • Cavernous hemangioma.

• Non-Axial Proptosis:

  • Eyeball moves forward in different direction

  • Fronto-ethmoidal lesion (Down & Out),

  • Lacrimal gland tumor (Down & In)(MC benign- Pleomorphic adenoma,Mc Malignant - Adenocystic Ca),

  • Maxillary Ca (Upwards).

  • Outward - Anterior Ethmoidocele

• Intermittent Proptosis:

• Orbital varices (enlarges on Valsalva).

• Pulsatile Proptosis:

  • Carotid-Cavernous Fistula,

  • Roof of orbit fracture,

  • Neurofibromatosis type 1 (Sphenoid dysplasia).

Pseudoproptosis

• High myopia - Increased eyeball size

• Shallow orbit

• Eyelid retraction - Thyroid eye disease /Horners syndrome

• Pseudoenopthalmos (Partial pstosis)

Intraorbital tumor

• Tumor Summary:

  • Pediatric:

    • Most common benign is Dermoid Cyst (Choristoma-normal tissue at abnormal place)→ MC location - superotemporal;

    • most common malignant is Rhabdomyosarcoma. Rx - chemo,radio

  • Adult:

    • Most common benign is Cavernous Hemangioma; Rx-Proanolol

    • most common malignant is Non-Hodgkin Lymphoma / Metastasis.

[ MC cause of uni/bi proptosis in adults - Thyroid eye disease

MC cause of Unilateral proptosis in child - Orbital cellulitis

MC cause of bilateral proptosis in children - Neuroblastoma ]