opthalmic anatomy Flashcards
what is pulsatile proptosis and causes
Pulsatile exophthalmos or pulsatile proptosis is a clinical symptom characterised by protrusion and pulsation of the eyeball that can occur due to various causes:
caroticocavernous fistulas neurofibromatosis type 1 (with sphenoid wing dysplasia) 2 arteriovenous malformation trauma (orbital roof fractures) 3 arachnoid cyst (rare) 4
how is the eye opened
CNIII oculomotor nerve supplies the LPS to open
how is the eye closed
CNVII facial nerve supplies the orbicularis oculi to close
What is retrobulbar haemorrhage
presence of a post septal orbital haematoma and is usually due to craniofacial trauma causing an extraconal haematoma. It may cause orbital compartment syndrome which is an ophthalmologic emergency.
what is orbital compartment syndrome
rapid rise in intraorbital volume and pressure,
reducing retinal and optic nerve blood flow. Unless urgently
decompressed, ischaemia rapidly ensues, potentially leading to
retinal infarction and permanent complete blindness
when to suspect orbital compartment syndrome (OCS)
examination findings
Any patient with an acute orbital injury is at risk of OCS.
Presenting features
rapid reduction in vision (with or without a RAPD),
tense, swollen lids, orbital congestion, and proptosis.
Other examination findings variably include periorbital haematoma,
restricted eye movements, high intraocular pressure,
(associated nausea or vomiting), chemosis and central retinal artery
occlusion.
what to do when you suspect OCS / treatment
Immediate decompression is required, with a lateral canthotomy
and cantholysis
to decompress the orbit and preserve ocular function
Immediate: lateral canthotomy (incision of the lateral canthal tendon) and lower ± upper cantholysis (disinsertion of the lateral canthal tendon) (see Box 3.1).
• If no improvement or if/worsens: IV mannitol (0.5–2g) and IV acetazolamide (500mg).
A common error that occurs with OCS
range imaging or medical treatment first,
this
delaying the only intervention which reduces the intraorbital pressure
when should one refer with OCS
Urgently refer to an orbital or maxillofacial surgeon for surgical
draining if perfusion does not return despite superior and inferior
cantholysis.
clinical features of retrobulbar syndrome
• Painful proptosis. • reduced vision. • resistance to retropulsion. • elevated IOP (>35mmHg). • relative afferent pupillary defect • restricted extraocular movements. • Tight eyelids. • retinal arterial pulsations.visual disturbance orbital bruising and swelling features of head and/or facial trauma
causes of retrobulbar syndrome
trauma - secondary to orbital fractures
orbital surgery
other surgery e.g. sinus or neurosurgical procedures
haemorrhage from an intraorbital vascular mass e.g. orbital vascular malformation or metastases
coagulopathies
what is pleomorphic adenoma of the lacrimal gland
(benign mixed tumor) is the most common epithelial neoplasm of the lacrimal gland.
slow growing, well-circumscribed, mass that is identical to its salivary gland counterpart
excellent prognosis for vision and long-term survival after complete surgical excision.
clinical features of pleomorphic adenoma of the lacrimal gland
slowly progressive and painless proptosis, with inferomedial displacement of the globe
visual disturbance possible with large tumours
sudden onset of pain may indicate malignant transformation
treatment for pleomorphic adenoma
Complete excision is curative, with an excellent prognosis. Incomplete excision is associated with high rates of recurrence.
differentials for a pleomorphic adenoma
other lacrimal gland masses
extralacrimal masses of the superolateral orbit such as dermoid/epidermoid cyst
CN III palsy presentations
down and out
pupils dialted
causes of CNIII palsy
increased intracranial pressure
aneurysms of PCA
vascular 2ry to diabetes, HTN - pupil sparing
cavernous sinus thrombosis
which cranial nerve has the longest route
trochlear as it emerges from the dorsal aspect of the brainstem
CN IV palsy
diplopia especially when looking down
causes of CNIV
head injury or increased ICP
what is horner syndrome
something impinging the sympathetic trunk
miosis
ptosis\anhidrosis
if someone comes with painful eye, face or neck with horner’s symptoms what is the causes and treatment
carotid dissection also causing the visual loss
call vascular team
weakest regions of the orbit
floor
medial wall
type of proptosis when its extraconal or intraconal
extraconal - non axial proptosis - pushing eye sideways or vertical displacement
intraconal - axial proptosis pushes it anteriorly
describe the surgical way of treating a squint
muscles can be shortened, realigned
CANNOT MOVE MORE THAN 3 MUSCLES AT A TIME
RISK ISCHAEMIA - IRIS CILIARY BODY CORNEAL LIMBUS
whats important with 6th nerve palsy
false localising sign for ICP as it comes of medulla pontinary junction
why do we have a blind spot
no photoreceptor cells in the optic nerve head - temporal visual field
what is surgical emphysema
air/gas located in the subcutaneous tissue
what is a chalazion
obstruction of the tarsal glands leading to painless swelling also called meiobian cyst
what is a stye
acute infection of Moll (sweat gland) or Zeiss (sebaceous glad) or eyelash follicle
tear path
lacrimal fluid entering the conjunctival sac thru duct into lacrimal lake medially into eye into lacrimal sal. nasla cavity thru nasolacrimal duct into nasopharynx
role of tear
provide a smooth ocular surface for light rays to be refracted uniformly and also provide lubrication to prevent friction between ocular surfaces during lid closure.
antibacterial action
components of a tear film
Surface lipid layer – secreted by the meibomian (tarsal) glands
Middle aqueous layer – secreted by the lacrimal gland and accessory lacrimal glands
Inner mucus layer – secreted by goblet cells of the conjunctiva and the epithelial cell surface
role of the lipid layer
prevents drying out as it stops evaporation
what happens if tarsal glands become obstructed
increase inevaporation drying th eyes out causing discomfot and grittiness
increase risk of damage and infection
causes of dry eyes
obstruction in tarsal glands - increased evaporation
reduced
reduced prod of tears
causes of red prod of tears
autoimmune diseases - Sjogren’s, RA
medications ie anithistamines
what are the layers of the eyeball
sclera
choroid
retina
what is the anterior chamber
space between the cornea and the iris
what is the posterior chamber
space between the iris and the ciliary body and the lens
what is the aqueous humour
ciliary body secretes this
fills the chambers of the eye
what are the muscles of the orbit
levator palpebrae superioris
FOUR RECTI
two oblique
the supplied by which CN
oculomotor - 3
trochlear - 4
abducen - 6
bloody supply to orbit
opthalmic artery - central artery to the retina
opthalmic veins - cavernous sinus
oculomotor palsy
ptosis
diplopia
role of the cornea
maintaining transparency
ocular protection
refraction of incoming light
