Orbit Flashcards
List the orbital openings.
- Optic foramen.
- Superior orbital fissure.
- Inferior orbital fissure.
- Tendinous ring (Annulus of Zinn)
Where is the optic foramen found?
Found on the lesser wing of the sphenoid bone.
What runs through the optic foramen?
- Optic nerve.
- Ophthalmic artery.
Where is the superior orbital fissure found?
Lies between the greater and lesser wings of the sphenoid bone.
What runs through the superior orbital fissure?
(LFTs)
- Lacrimal nerve (CNV1).
- Frontal nerve (CNV1).
- Trochlear nerve (CN4).
- Superior ophthalmic vein.
Where is the inferior orbital fissure found?
Lies between the maxilla and the greater wing of the sphenoid.
What runs through the inferior orbital fissure?
- Inferior ophthalmic veins.
- Infraorbital nerve (CNV2).
- Zygomatic nerve (CNV2).
What runs through the tendinous ring (annulus of Zinn)?
- CN3 upper division.
- Nasociliary nerve (CN5a).
- CN3 lower division.
- CN6.
Which bones make up the roof of the orbit?
‘Front S’
- Frontal bone.
- Lesser wing of the sphenoid.
Which bones make up the medial wall of the orbit?
‘SMEL’
- Sphenoid.
- Maxillary.
- Ethmoid.
- Lacrimal.
Which bones make up the floor of the orbit?
‘My Zipped Pants’
- Maxillary.
- Zygomatic.
- Palatine.
Which bones make up the lateral wall of the orbit?
‘Greater Z’
- Greater wing of the sphenoid.
- Zygomatic.
Which aspect of the orbit is weakest? Why?
- Medial wall.
- Has a thin transparent membrane called the lamina papyracea through which infection can easily spread.
- This is how ethmoid cellulitis can lead to orbital cellulitis.
What is the hallmark of orbital disease?
Eyeball sitting abnormally in the socket.
What is a Herten exophthalmometer? What is considered abnormal?
Machine used to measure the protrusion of the globe in the orbit.
> 20mm indicates proptosis.
What are the 3 types of exophthalmos?
- Axial proptosis.
- Non-axial proptosis.
- Pseudoproptosos.
What is axial proptosis?
Straight out.
What does axial proptosis indicate?
Lesion within the tendinous ring such as optic nerve glioma and cavernous haemangioma.
What is non-axial proptosis?
Protrusion at an angle.
What does non-axial proptosis indicate?
Lesion outside the tendinous ring such as the lacrimal gland.
What is pseudoproptosis? Why does this happen?
- False appearance of proptosis.
- Typically due to facial anatomy.
What is the difference between proptosis and exophthalmos?
Proptosis is the protrusion of any organ whereas exophthalmol is proptosis of the eye.
What is enophthalmos?
Sunken eyes, opposite of exophthalmos.
What causes enophthalmos?
Can be congenital as a result of atrophy of the ocular contents.
When may pseudoenophthalmos be seen?
Can be seen in a small eye (microphthalmos), ptosis or proptosis of the fellow eye.
What are the two types of cellulitis seen in ophthalmology?
Preseptal and orbital.
What is the main difference between preseptal and orbital cellulitis?
Orbital cellulitis is severe and preseptal cellulitis is mild.
Where does preseptal cellulitis occur as opposed to orbital cellulitis?
Preseptal: anterior to the orbital septum.
Orbital: eye socket behind the orbital septum.
What typically causes preseptal cellulitis as opposed to orbital cellulitis?
Preseptal: direct infection from lid trauma (Staph aureus).
Orbital: infection via air sinuses (ethmoid sinus) by Strep pneumoniae or H. influenzae.
How do patients present in preseptal cellulitis as opposed to orbital cellulitis?
Preseptal: lid inflammation and low-grade fever, no signs of eye involvement.
Orbital:
- Children.
- Acutely inflamed orbit.
- Proptosis.
- Fever.
- Restricted ocular movements.
- Defects in vision.
- RAPD.
How is preseptal cellulitis treated as opposed to orbital cellulitis?
Preseptal: PO antibiotics.
Orbital: IV antibiotics (admit due to risk of progression into brain).
How are preseptal and orbital cellulitis anatomically demarcated?
Demarcated by the orbital septum.
This is a membrane that extends from the orbital rim and inserts into the eyelid.
What is the most common cause of axial proptosis in adults?
Thyroid eye disease.
What are the stages of thyroid eye disease?
- Active inflammatory stage - eyes are red and painful.
- Fibrotic phase - oedema and fibrosis, leading to restrictive myopathy, exophthalmos and optic neuropathy. Involved extraocular muscles.
What is the pathophysiology of thyroid eye disease?
TSH IgG binds to TSHr on extraocular muscles and fibroblasts > leads to adipogenesis and hyaluronic acid deposition in orbital muscle > leads to swelling of muscles and fat.
What causes lid retraction in thyroid eye disease?
Sympathetic overstimulation of Muller’s muscle.
What is the single biggest risk factor for thyroid eye disease?
Smoking.
Which condition is most associated with thyroid eye disease?
Superior limbic keratoconjunctivitis.
N.B., around half of these patients will also have thyroid eye disease.
Describe the presentation of thyroid eye disease.
- Hyperthyroid typically (not always).
- Axial proptosis.
- Lid retraction (Dalrymple sign).
- Lid lag (Von Graefe sign).
- Characteristic staring appearance (Kocher sign).
- Restrictive myopathy typically affects the inferior rectus first.
What is Kocher sign?
Characteristic staring appearance.
What is Von Graefe sign?
Lid lag.
What is Dalrymple’s sign?
Lid retraction.
Which muscle is affected first and most commonly in thyroid eye disease?
Inferior rectus.
Which investigations are used to diagnose thyroid eye disease?
- CT of the orbit > thickening of extraocular/levator muscle and sparing of the tendons.
- Anti-TSHr antibody.
Describe the management of severe/acute thyroid eye disease.
- IV methylprednisolone followed by oral prednisolone.
- Orbital radiation if steroids are contraindicated.
Describe the management of mild/chronic thyroid eye disease.
- Lubricants.
- Taping - to minimise exposure keratopathy.
- Topical cyclosporine to reduce inflammation.
- Aim for euthyroid.
Describe the management of the fibrotic phase of thyroid eye disease?
Orbital decompression surgery.
When do we initiate management for severe/acute thyroid eye disease?
If there are signs of optic neuropathy:
- Dyschromatopsia.
- RAPD.
- Field and acuity defects.
What are three other causes (aside from thyroid eye disease and cellulitis) that can cause orbital inflammation?
- Tolosa-Hunt syndrome.
- Granulomatosis with polyangiitis (Wegener’s granulomatosis).
- Sarcoidosis.
What is Tolosa-Hunt syndrome? What is it caused by?
- Syndrome of headache, ophthalmoplegia and periorbital sensory loss.
- Caused by granulomatous inflammation of the orbit, cavernous sinus or superior orbital fissure.
What is the key feature of Tolosa-Hunt syndrome?
Dramatic response to steroids.
What is granulomatosis with polyangiitis (Wegener’s)?
Multisystem necrotising vasculitis that typically affects the upper respiratory tract, kidneys and lungs.
What is the key feature of granulomatosis with polyangiitis (Wegener’s)?
C-ANCA positive in most cases.
What is sarcoidosis?
Multisystem non-caseating granulomatous disorder that manifests in the eye as uveitis.
What is the key feature of sarcoidosis?
- Elevated serum ACE and calcium.
- Bilateral hilar lymphadenopathy on chest x-ray.
What are the 4 types of childhood orbital tumour?
- Rhabdomyosarcoma.
- Neuroblastoma.
- Capillary haemangioma.
- Optic nerve glioma.
What is a rhabdomyosarcoma?
Commonest primary childhood orbital malignancy.
What does a rhabdomyosarcoma affect?
Most commonly affects the genitourinary system and the head and neck.
Where does an orbital rhabdomyosarcoma typically present?
Superonasal orbit.
How does orbital rhabdomyosarcoma present?
Rapidly progressive, painless, unilateral proptosis with down and out displacement of the eyeball.
What is a neuroblastoma?
Tumour of neural crest cells that can metastasise to the orbit from elsewhere in the body.
How can neuroblastoma be identified histologically?
Homer-wright rosettes.
What is a capillary haemangioma?
High flow vascular hamartoma which grows rapidly in infancy.
Completely resolve at around age 8.
How does capillary haemangioma present?
Blanching, red, unilateral lesion of the upper lid.
When should capillary haemangioma be treated? How?
- If small and no risk of affecting the visual axis > observation is sufficient.
- If there is a risk of amblyopia > propranolol can be used to increase the rate of lesion regression.
What is an optic nerve glioma?
Tumour of the glial tissue of the optic nerve, associated with NF1.
How does optic nerve glioma present?
Slowly progressing unilateral proptosis with visual defects and RAPD.
What does a CT show in optic nerve glioma?
Characteristic fusiform enlargement of the optic nerve.
What are the two types of adulthood orbital tumour?
- Optic nerve sheath meningioma.
- Cavernous haemangioma.
What is an optic nerve sheath meningioma?
Tumour of the meningeal tissue of the optic nerve.
How does optic nerve sheath meningioma present?
Presents with triad:
- Painless, unilateral vision loss.
- Optic nerve atrophy.
- Optociliary shunting of vessels.
- Middle-aged woman.
Which investigations are used to diagnose optic nerve sheath meningioma? What do they show?
- CT.
- Shows thick optic nerve sheath and osteoblastic changes.
What is a cavernous haemangioma?
Low-flow hamartoma within the common tendinous ring.
How does cavernous haemangioma present?
- Slowly progressive axial proptosis.
- Decreased visual acuity.
- Middle-aged woman.
Which investigations are used to diagnose cavernous haemangioma? What do they show?
- CT.
- Shows defined lesion within the common tendinous ring.
What is the cavernous sinus?
Venous structure in the brain made up of a network of hollow spaces that drain blood away from the brain.
What is a carotid cavernous fistula?
An arteriovenous malformation between the carotid artery and the cavernous sinus.
What are the 2 types of carotid cavernous fistula? How do we differentiate between them?
- Direct and indirect.
- Angiogram is done to provide a definitive diagnosis.
What is a DIRECT carotid cavernous fistula?
High flow direction connection between the internal carotid artery and the cavernous sinus.
What is an INDIRECT carotid cavernous fistula?
Low flow connection between internal carotid artery and the cavernous sinus VIA meningeal branches.
What typically causes DIRECT carotid cavernous fistula?
Trauma.
What typically causes INDIRECT carotid cavernous fistula? Who does it appear in?
Spontaneous in elderly hypertensive women.
How does DIRECT carotid cavernous fistula present?
- Ocular bruit - whooshing sound heard by the patient.
- Raised IOP.
- Visual defects.
How does INDIRECT carotid cavernous fistula present?
- Gradual onset irritated eye.
- Increased IOP.
- Corkscrew epibulbar vessels.
How is DIRECT carotid cavernous fistula managed?
Embolisation.
How is INDIRECT carotid cavernous fistula managed?
Most cases self-resolve.
Where does the internal carotid travel that makes it so significant in carotid cavernous fistula?
Within the cavernous sinus.
What is the cavernous sinus in terms of CST?
Venous blood sinus that is prone to thrombosis. Lots of important structures travel within this sinus.
What is a cavernous sinus thrombosis? What causes it?
A clot within the cavernous sinus.
Typically caused by spreading infection.
Describe the presentation of cavernous sinus thrombosis.
- Acute onset headache.
- Nausea.
- Proptosis.
- Diplopia.
What causes the characteristic symptoms of cavernous sinus thrombosis?
Thrombosis causes compression of CN3, CN4 and CN6 as they traverse the sinus.
Which investigation is diagnostic for cavernous sinus thrombosis?
MRI with MRI venogram.
Which cranial nerve is affected (compressed) first in cavernous sinus thrombosis? Why?
CN6 - travels within the sinus as opposed to CN3 and CN4 which travel within the walls of the sinus.
What is the management of cavernous sinus thrombosis?
- Antibiotics.
- Steroids.
- Thrombolytics.
- Surgical drainage.
What are orbital varices?
Venous enlargements within the orbit.
How do orbital varices present in terms of distribution?
- Unilateral.
- Medial.
What is the key defining feature of orbital varices?
Intermittent proptosis.
What worsens orbital varices?
Valsalva manoeuvre.
What are the 5 types of ocular trauma?
- Intraocular foreign bodies (IOFB).
- Burns.
- Orbital floor fractures.
- Retrobulbar haemorrhage.
- Hyphaema.
What is the most ocular toxic metal?
Copper.
What can be caused by alloys of copper?
- Sunflower cataracts.
- Kayser-Fleischer rings.
What are the effects of iron on the eye?
Deposits in the ocular epithelial tissue:
- Cell death > glaucoma, cataract and retinal detachment.
What are some inert foreign bodies?
- Glass.
- Plastic.
- Stone.
- Silver.
- Gold.
- Platinum.
- Lead.
Which metals have mild toxic effects on the eye?
- Aluminium.
- Zinc.
Which investigations are diagnostic for intraocular foreign bodies?
- CT/x-ray in ALL cases.
- Visual evokes potential testing > reduced b-wave in some cases of chronicall retained IOFB.
Which investigation is contraindicated in intraocular foreign body?
MRI as some bodies can be magnetised.
What is the priority in terms of management with a penetrating injury?
Repair of the globe.
What does foreign body removal technique depend on?
The location of the foreign body.
Which removal technique is used for a foreign body in the cornea?
26G needle.
Which removal technique is used for a foreign body in the anterior chamber?
Fine forceps.
Which removal technique is used for a foreign body in the angle of the anterior chamber?
Scleral trapdoor approach.
Which removal technique is used for a foreign body in the ciliary body?
Electromagnetic removal.
Which removal technique is used for a foreign body in the posterior segment?
Intraocular magnet or vitrectomy forceps.
What are the two substances that can cause ocular burns?
Alkalis and acids.
Which substance causes significantly worse burns?
Alkalis.
What kind of necrosis is caused by alkalis?
Liquefactive necrosis.
What kind of necrosis is caused by acids?
Coagulative necrosis.
What aids corneal healing?
Migration of limbal stem cells. If the limbus is damaged then healing is hindered.
What are the steps in managing ocular burns?
- Irrigation with copious amounts of water.
- Antibiotics + cycloplegics + lubricants + analgesia.
- Topical steroids.
- Ascorbic acid (not to be used in acid burns) - aids collagen formation and mops up free radicals.
- Doxycycline - proteinase (MMP) inhibitor which aids healing.
Which management techniques are used for prolonged corneal healing problems?
- Amniotic membrane transplant.
- Limbal stem cell transplant.
Why is topical sodium citrate useful in healing ocular burns? Why is it not used?
- Inhibits collagenases and aids healing.
- Administration is painful so not in common use.
What is the classic mechanism of orbital floor fractures?
Ball/fist injury to the eye.
What is the consequence of an orbital floor fracture?
- Soft tissue of the globe is pushed into the maxillary sinus.
- Inferior rectus can be entrapped, causing vertical diplopia and restriction of eye elevation.
When does surgical emphysema occur?
- Orbital floor fractures.
- More pronounced in medial wall fractures.
Describe the presentation of orbital floor fractures.
- Periorbital bruising.
- Vertical diplopia and extraocular muscle entrapment.
- Enophthalmos.
- Infraorbital anaesthesia.
Which investigation is diagnostic for orbital floor fractures?
CT.
What is used in monitoring and follow-up of orbital floor fractures?
Hess charts.
What is the typical presentation of extraocular muscle entrapment?
Antagonistic movement is restricted.
e.g., if the superior rectus is trapped, downgaze is restricted.
What are the indications for surgery on orbital floor fractures?
- Oculocardiac reflex.
- Severe facial destruction.
When can observation suffice for orbital floor fractures?
- Minimal diplopia.
- Minimal enophthalmos.
What should patients with orbital floor fractures be advised?
To avoid blowing their nose.
What is retrobulbar haemorrhage and why is it an emergency?
- Intra-orbital bleeding/swelling.
- The bony orbit is a rigid chamber so this can lead to a sharp rise in pressure > blindness.
What is the pathology of retrobulbar haemorrhage?
- Trauma causes oedema/bleeding in the orbit and leads to a sharp rise in intraorbital pressure.
- Rising intraorbital pressure restricts blood flow and causes optic nerve damage.
- Process can be thought of as orbital compartment syndrome.
Describe the presentation of retrobulbar haemorrhage.
- Painful loss of vision.
- Rigid proptosis.
- Restricted ocular movements.
- RAPD.
- Elevated intraocular pressure.
Which investigation is diagnostic of retrobulbar haemorrhage?
Radioimaging.
However, this should not delay treatment.
What is the immediate management of retrobulbar haemorrhage?
- IV mannitol.
- IV acetazolamide.
- IV methylprednisolone.
If medications fail to work, what is the next management for retrobulbar haemorrhage?
Lateral canthotomy and cantholysis.
What is cantholysis?
Disinsertion (rupture) of the lateral canthal tendon. This procedure allows the release of intraorbital pressure.
If canthotomy and cantholysis fail to work, what is the next management for retrobulbar haemorrhage?
Orbital decompression.
What is hyphaema? What causes it?
Blood in the anterior chamber. Most commonly caused by blunt trauma.
What is hyphaema a sign of?
Ocular trauma.
Warrants investigation.
What is microhyphaema?
Erythrocytes are only visible on a slit lamp.
What are the risk factors for hyphaema (things to check for)?
- Drug history - anticoagulants.
- PMH - coagulative disorders and sickle cell.
When is treatment required for hyphaema?
Only required in high risk cases.
What is considered a high risk case for hyphaema?
- Children.
- Rebleeds.
- Risky medical histories.
What is the treatment for hyphaema?
- Admit for steroids and bedrest.
- Monitor IOP for red cell glaucoma.
If medications fail for hyphaema, what can be tried next?
Anterior chamber paracentesis.
If AC paracentesis fails for hyphaema, what can be tried next?
Trabeculectomy.
