orbit Flashcards
what makes the roof lateral wall floor medial wall of the orbit
● Roof: Frontal bone and lesser wing of the sphenoid.
● Lateral wall: Zygomatic bone and greater wing of the sphenoid.
● Floor: Zygomatic, maxillary and palatine bones.
● Medial wall: Maxillary, lacrimal, sphenoid and ethmoid bones. The lamina
papyracea is a paper-thin plate which covers the ethmoidal cells and forms a part of the medial wall. It can act as a route of entry for infection from the ethmoid sinus.
name the 3 orbital openings
optic foramen
superior orbital fissure
inferior orbital fissure
what goes thru the optic foramen and where is it based
Located within the lesser wing of the sphenoid.
It transmits the optic nerve and ophthalmic artery into the middle cranial fossa.
SOF comprise
LFTS
- Lacrimal nerve
- Frontal nerve
- Trochlear nerve
- Superior branch of ophthalmic vein
Contains the superior ophthalmic vein, the lacrimal nerve (CNV1), the frontal nerve (CNV1) and the CNIV.
– Note: The frontal nerve branches into the supraorbital and supratrochlear nerves. The supraorbital nerve leaves the orbit via the supraorbital notch
what does the inferior part of SOF comprise
Contains CNIII, the nasociliary nerve (CNV1) and CNVI.
what does IOF comprise and locations
- Branches of pterygopalatine ganglion
- Inferior ophthalmic vein
- Zygomatic nerve
- Maxillary nerve
Located between the maxilla and the greater wing of the sphenoid bone. It contains the infraorbital nerve (CNV2), the zygomatic
nerve (CNV2) and the inferior ophthalmic vein.
– Note: The infraorbital nerve exits the orbit via the infraorbital
foramen.
where is annulus zinn located and comprises
“Several Orbital Nerves In One Annulus” • Superior division of Oculomotor nerve • Nasociliary nerve • Inferior division of Oculomotor nerve • Abducens nerve
- surrounding the optic canal and the inferior part of the SOF is the common tendinous ring
fibrous tissue marking the origin of the four recti muscles
CNII, CNIII, CNVI and the nasociliary nerve.
retrobulbar anaesthetic block affects which nerves
inside the common tendinous ring/annulus of zinn
what is the orbital septum and location
It is a membranous sheet that forms the fibrous part of the eyelids.
The orbital septum is located anterior to the orbit and extends from the orbit rims to the eyelid.
what is thyroid eye disease and its cause and peak incidence
most common cause of unilateral and bilateral axial proptosis in adults.
idiopathic autoimmune disorder
30-50 years
what are the phases of TED
active inflammatory phase (months-years) in which the eyes are red and painful,
inactive fibrotic phase that involves extraocular muscles (EOM) and connective tissues.
RFs of thyroid eye disease
● Smoking
● Females
● HLA-DR3 and HLA-B8
pathophysiology of thyroid eye disease
● Sympathetic overstimulation of the Müller muscle due to high levels of thyroid hormones causing eyelid retraction.
● Fibroblastic deposition of glycosaminoglycans into the EOM producing oedema and eventual fibrosis of EOM. This leads to:
Impaired movement of EOM (restrictive myopathy).
Exophthalmos which exposes the cornea causing dryness, irritation and exposure keratitis.
Lid retraction due to fibrosis of levator palpebrae.
Increased pressure on the optic nerve causing optic neuropathy. Impaired venous drainage leading to conjunctival and periorbital oedema and conjunctival injection.
clinical features of thyroid eye disease
● Unilateral/bilateral axial proptosis, redness, chemosis and ocular irritation.
● Lid retraction (Dalrymple sign).
● Lid lag on downgaze (Von Graefe sign).
● ‘Staring’ appearance (Kocher sign).
● Restrictive myopathy: EOM is usually affected in the following order: inferior rectus (IR), medial rectus (MR), superior rectus (SR), levator palpebrae, lateral rectus (LR).
● Choroidal folds (rare).
Ix for thyroid eye disease
● Thyroid function tests.
● Imaging
CT or MRI are indicated if orbital decompression is planned, to help confirm an equivocal diagnosis or if there is asymmetry on exophthalmometry. Shows thickening of EOM bellies (most commonly IR and MR) with characteristic tendon sparing.
● Visual field testing is indicated, especially if optic neuropathy is suspected.
classification of TED and the name
European Group on Graves’ Orbitopathy (EUGOGO)
into severe sight-threatening (optic neuropathy)
moderate-severe (exophthalmos ≥3 mm, lid retraction ≥2 mm and/or diplopia) and mild disease.
General measures of TED
● Smoking cessation.
● Achieve euthyroid status.
Mx for mild disease TED
● Watchful waiting.
● Ocular lubricants during day and overnight to avoid dryness and ulceration
● Topical ciclosporin to reduce ocular irritation.
● Overnight lid taping for mild exposure keratopathy.
● Selenium supplements can improve the course of TED
Mx for moderate severe disease TED
● IV methylprednisolone ± oral prednisolone: Bisphosphonates should be considered in patients receiving steroid therapy due to risk of osteoporosis. It is important to check liver function in patients receiving high doses of IV steroids.
● Orbital radiotherapy: Can be used in combination with steroids or when steroids are contraindicated in patients with active TED complaining of diplopia or restricted eye movements. Orbital irradiation can increase risk of retinopathy in diabetic and hypertensive patients.
surgical measures for mod-sev disease for TED
Surgery is indicated after inflammatory phase subsides (i.e. in the inactive phase), in cases of optic neuropathy, significant proptosis, persistent diplopia or severe lid retraction.
The following order is recommended if surgery is indicated:
– Orbital decompression
– Strabismus surgery
– Eyelid surgery
complications and associations of TED
● Dysthyroid optic neuropathy: Causes severe sight-threatening TED, suspect if there are changes in colour vision or VA with presence of optic disc swelling and relative afferent pupillary defect (RAPD). Treatment is with IV steroids and orbital decompression (if unresponsive to IV steroids).
● Exposure keratopathy: Manage with lubricants, surgery (e.g. tarsorrhaphy) or botulinum toxin injections.
● Superior limbic keratoconjunctivitis: A common association with TED.
what is obrital cellulitis
Infection of the soft tissues of the eye socket behind the orbital septum
within the orbit but not affecting the globe
aetiology of orbital cellulitis
Spread of infection from paranasal sinuses most commonly ethmoidal sinus
common organisms in orbital
- Streptococcus pneumoniae
- Staphylococcus aureus
- Haemophilus influenzae
features of orbital cellulitis
• Children are most commonly affected
• Acute onset of swelling of orbital tissue, chemosis - limited eye movement
- proptosis
• Fever, tenderness and restricted eye movement
• RAPD, decreased colour vision, dVA and diplopia may occur
Ix for orbital cellulitis
CT scan
Mx for orbital cellulitis
Admit for IV antibiotics (e.g. ceftriaxone + flucloxacillin + metronidazole)
if orbit needs to be drained then refer to ENT
complications of orbital cellulitis
- Orbital abscess - Cavernous sinus thrombosis - Brain abscess and meningitis - Optic neuropathy - central retinal artery occlusion
what is preseptal cellulitis
Infection isolated anterior to the orbital septum
superficial tissue injury
aetiology of preseptal cellulitis
Direct inoculation from eyelid trauma
common organisms of preseptal cellulitis
Staphylococcus aureus
Streptococcus pyogenes
Streptococcus pneumoniae
features of preseptal cellulitis
- painful swollen lid
- maybe unable to open eye
• Patient presents with eyelid oedema and erythema - low- grade fever
Ix for preseptal cellulitis
CT scan if doubtful diagnosis
Mx for preseptal cellulitis
Oral antibiotics (e.g. co-amoxiclav)
complications of preseptal cellulitis
Can progress to orbital cellulitis
RFs for orbital cellulitis
previous URTI/sinus infection (ethmoidal)
lack of Hib vaccination
mena age hospitilisation 7-12 years
what features distinguish between preseptal cellulitis from orbital cellulitis
• Important distinctions from orbital cellulitis include normal eye movement, normal VA and colour saturation, absence of proptosis and absent of RAPD
what is orbital mucormycosis
fungal infection
more gradual onset and in immunocompromised patients or patients with diabetic ketoacidosis.
pathogen involved in mucormycosis
mucoraceae
Sx of orbital mucormycosis
Mx
orbital swelling and signs of orbital cellulitis. Characteristically, necrotic black eschars over the nasal turbinates or palate can form.
IV antifungals
surgical debridement
what is rhabdomyosarcoma
most common primary orbital malignancy in children.
onset age mean 8 years
most common affected areas for rhabdomyosarcoma
genitourinary system and the head and neck (including orbit).
histopathology of rhabdomyosarcoma
This tumour has the ability to differentiate into striated muscle from undifferentiated mesenchymal cells. Embryonal is the most common subtype and is characterized by elongated spindle-shaped cells (‘strap cells’)
clinical features of rhabdomyosarcoma
● Rapidly progressive unilateral proptosis.
● Most common location in the orbit is superonasal.
● Diplopia may occur.
Ix for rhabdomyosarcoma
● MRI or CT: Shows a circumscribed mass ± bone erosion.
● Biopsy.
what is a neuroblastoma
most common extracranial solid tumour in children and is derived from the neural crest cell of the sympathetic nervous system
neuroblastoma commonly occurs where
adrenal medulla secreting catecholamines but can also involve the
head, neck, chest abdomen or spine. It usually metastasises to the orbit.
histology of neuroblastoma
Homer-Wright rosettes.
clinical features of neuroblastoma
Child with unilateral/bilateral proptosis and periorbital
ecchymosis (racoon eyes). Differential for basal skull fracture.
associations of neuroblastoma
Opsomyoclonus, a rare neurological syndrome characterized by conjugate jerky eye movements (dancing eyes) and cerebellar ataxia (dancing
feet).
what is lymphangioma
Rare vascular hamartomatous tumours which may form blood-filled ‘chocolate’ cysts. They present in childhood and depend on whether the lesion is anterior or posterior.
what is anterior lymphangioma
Soft bluish mass superonasally on eyelid or conjunctiva which are exacerbated by Valsalva manoeuvre.
what is posterior lymphangioma
Insidious growth may lead to proptosis. Presentation can be with painful proptosis due to spontaneous haemorrhage.
what types of tumors can arise from the optic nerve
glial tissue - optic nerve glioma
meninges - optic nerve meningioma
what is carotid-cavernous fistula (CCF)
Development of an AV connection between cavernous sinus (venous) and the carotids ( arterial)
direct or indirect
what is optic nerve glioma
Slow-growing benign tumour which typically affects children
associations of optic nerve glioma
neurofibromatosis 1
clinical features of optic nerve glioma
Gradual painless
monocular proptosis
visual loss and RAPD
Optic nerve head can be
initially swollen but then becomes atrophic
Ix for optic nerve glioma
CT: Fusiform enlargement of the optic nerve
what is optic nerve sheath meningioma
Slow-growing benign tumour which typically affects middle-aged females
associations of optic nerve sheath meningioma
Neurofibromatosis 2
clinical features of optic nerve sheath meningioma
Pathogenomic triad of
- progressive
- painless
- unilateral visual loss + optic atrophy + optociliary shunt vessels
proptosis may also occur
Ix for optic nerve sheath meningioma and what would u see
CT: Thickening of the optic nerve sheath (‘tram-track’ sign) and osteoblastic changes
what is direct CCF
A high-flow arteriovenous fistula or communication between the cavernous sinus and internal carotid artery directly
aetiology of direct CCF
Usually due to trauma (can be spontaneous)
features of direct CCG
• Acute onset following head injury • Triad • Pulsatile proptosis with associated bruit • Conjunctival chemosis • Whooshing sound in head • Ophthalmoplegia (due to cranial nerve damage) • Raised IOP • Papilloedema • Visual loss
Ix for CCF and what will u see
• CT/MRI: Dilatation of the
superior ophthalmic vein
• Definitive diagnosis: MRA,
CRA or angiography
Mx for direct CCF
Transarterial repair of the artery
embolization
complications of CCF
- Immediate visual loss due to optic nerve damage at the onset of head injury
- Delayed visual loss can be due to open-angle glaucoma (most common cause of visual loss)
what is indirect CCF
A low-flow arteriovenous fistula or communication between meningeal branches of the internal/external carotids and the cavernous sinus
aetiology of indirect CCF
Usually spontaneous and most commonly in hypertensive elderly women
features of indirect CCG
• Gradual onset of redness and irritation of the eyes
• Raised IOP
• Moderate venous
dilatation with later tortuosity of retinal vasculature
• Corkscrew epibulbar vessels
• Mild proptosis
Ix for indirect ccf
• CT/MRI: Dilatation of the
superior ophthalmic vein
• Definitive diagnosis: MRA,
CRA or angiography
Mx for indirect CCF
- Spontaneous resolution in about half of the cases
* Monitor IOP and VA
what is cavernous haemangioma
most common benign hamartoma of the orbit in adults. It is a low- flow arteriovenous malformation.
where is cavernous haemangioma found and who is it common in
muscle cone lateral to the optic nerve
common in middle aged females
features of cavernous haemangioma
● Slowly progressive axial proptosis. Most notable during pregnancy.
● Induced hypermetropia due to globe indentation.
● Optic nerve compression may occur, leading to decreased VA (dVA).
● Extraocular muscle restriction leading to diplopia.
Ix for haemangioma
● USS shows a well-defined intraconal lesion with increased reflectivity.
● CT or MRI can show a well-circumscribed lesion, typically intraconally.
Mx for cavernous haemangioma
surgical excision if vision is affected
what is capillary haemangioma
A type of hamartoma; the most common benign orbital tumour of infancy. These are high-flow endothelial neoplasms which undergo rapid growth due to vascular endothelial growth factor soon after birth.
● May be superficial (‘strawberry naevi’) or deep (posterior to orbital septum).
● More common in boys.
● Rapid growth in early infancy (2 months–1 year) with spontaneous
regression by 7 years of age.
clinical features of caoillary haemangioma
● Bright red unilateral lesion on upper eyelid which blanch with pressure or enlarge when the child cries (Valsalva).
● Ptosis due to its location in the upper lid.
● Deep lesions, however, are dark blue/purple in colour and can cause axial
proptosis.
Mx for capillary haemangioma
● Observation: Most resolve spontaneously.
● If risk of amblyopia, cosmetic reasons or anisometropic astigmatism
Propranolol
Corticosteroid injections or systemic steroids Surgical excision
what is cavernous sinus thrombosis
clot formation within the sinus and is mainly due to a spreading infection from the paranasal sinuses, ear or pre- existing orbital cellulitis.
clinical features of cavernous sinus thrombosis
● Rapid-onset headache, nausea, vomiting, chemosis and dVA.
● Unilateral or bilateral proptosis.
● Diplopia due to CNIII, CNIV or CNVI compression. CNVI is first to be
affected, as it lies freely within the cavernous sinus, causing a lateral gaze palsy.
Ix for cavernous sinus thrombosis
● MRI and MRI venography to confirm diagnosis.
Mx for cavernous sinus thrombosis
● Intravenous antibiotics, steroids and/or low-molecular-weight heparin.
● Surgical drainage.
complications of cavernous sinus thrombosis
● Meningitis
● Septic emboli
● CNS deficits
