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)
