8. Eye & pathology Flashcards
how could acute sinusitis spread into the orbit?
via ethmoid sinus
why is diplopia worse on vertical gaze in orbital blowout fracture?
physical entrapment of structures under eyeball
management of orbital blowout fracture
CT orbit
refer to opthalmology
prophylactic antibiotics
avoid nose blowing, valsalva manoeuvres and driving until diplopia resolves
follow up 1 week: entrapment enopthalmos and diplopia should improve
or surgical repair after 1-2 weeks if not
which cranial nerve and artery/vein is transmitted by
1. optic canal
2. superior orbital fissure
3. inferior orbital fissure
- optic nerve, ophthalmic artery
- Va branches, CN 3,4,6, superior ophthalmic vein
- infraorbital nerve Vb, inferior ophthalmic vein
how can venous blood spread from orbit to cavernous sinus?
superior opthalmic vein
main arterial supply to orbit and eye
ophthalmic artery, central retinal artery
location of central retinal artery
runs inside optic nerve to retina
what males up the eyelid?
skin, subcutaneous tissue, muscles, tarsal plate
key muscles of eyelid
orbicularis oculi
levator palpeerde superioris
where are meibomian glands?
within tarsal plate
treatment of
-meibomian cyst
-stye
-nothing, or surgery is persists
-warm compress, maybe oral ABx
is a stye painful?
yes
blepharitis
-what is it
-cause
-signs
-treatment
-inflamamtion of eyelid margin
-staph, meibomian gland dysfunction
-crusting, dry eyelids, swollen, red
-warm compress and lid hygiene
where is periorbital cellulitis? is ocular function affected?
superior to orbital septum
no
what to do if unsure periorbital cellulitis vs post septal
refer urgently
where is orbital cellulitis?
within orbit or deep to orbital septum
signs of orbital cellulitis, why do they occur?
proptosis/exopthalmos
reduce painful eye movements
reduced visual acuity
optic never and extrapcular muscles involved
big risk of orbital cellulitis
route for infection to spread intracranially, and cause
-cavernous sinus thrombosis
-meningitis
-permanent blindnes via optic nerve damage
management of orbital cellulitis
admit
IV ABx
maybe surgical management if abscess
3 layers of tear film, and what produces them
- oily: meibomian glands
- water: lacrimal glands
- mucus: goblet cells in conjunctiva
epiphora
obstruction to drainage of tear film
conjunctivitis
-cause
-pain?
-symptoms
-infectious?
-viral, infection of conjunctival membrane
-no
-uncomfortable, gritty, red
-yes
sub conjunctival haemorrhage
-pain?
-cause
-no
-spontaenous hurts conjunctival blood vessel
pigmented part of eye
iris
how is central vision achieved?
light focussed onto macula and fovea
retinal ganglion cell axons exit the eye as what?
optic nerve via optic disc
central retinal artery occlusion
sudden unilateral painless loss of sight, e.g. embolus preventing blood supply to retinal blood vessels
nerve supply to retina
choroid blood vessels
retinal blood vessels
fundoscopy view of central retinal artery occlusion
cherry red spot: macula accentuated as choroid seen more clearly against pale retina
pale retina: ischaemia
why does blockage of drainage of aqueous humor cause raised IOP?
ciliary body keeps producing, but cant drain away
fundoscopy of glaucoma
raise IOP causes optic disc cupping
is glaucoma sight threatening?
closed angle is
signs of acute closed angle glaucoma
acute painful red eye
fixed oval space pupil
blurring
halos round lights
nausea, vominting
usually older patient
treatment of acute closed angle glaucoma
drugs to rescue IOP then surgery
factors needed for sight, and what controls them
- regulate light entry- pupil
- reaction: tear film, cornea, lens
- shape eyeball
how does lens become more biconvex?
contraction of ciliary muscle, relaxation of suspensory ligaments
phototransduction
conversion of photons to APs via photoreceptors
blind spot
optic disc (no photoreceptors)
lobe of brain APs sent to for visual interpretation
occipital
causes of decreased visual acuity
-opacity of strictures anterior to retina
-redcued refractive ability of structures anterior to retina
-retina/optoc nerve damage
examples of reduced refractive ability of structures anterior to retina
-irregularity of cornea surface: astigmatism
-age related lens stiffness: presbyopia
-shape of eyeball
examples of retina/optic nerve problems
-retinal detachment
-age related macular degeneration
-optic neuritis
red reflex
checks transparency os structures using opthalmoscope
how to test if decreased visual acuity is a refractive problem or not?
(i.e. transparency OK)
pin hole test- repeat snellen chart by looking through pinhole which allows light to only enter perp to cornea and lens
light doesn’t need reaction, so if result improves, problem was refractive
why do we have binocular vision?
-wider field of vision
-depth perception
conjugate eye movement
eyes coordinate so images from both hit same spot on retina
diplopia
misalignment of two visual axes, focus on different areas of retina so brain cant fuse, see 2 images
SR actions
elevate
adducts
intorts
IR actions
depress
adducts
extorts
SO actions
depress
intort
abducts
IO actions
elevate
extort
abduct
strongest elevator when eye is adducted
IO
strongest depressor when eye is adducted
SO
strongest elevator when eye is abducted
SR
strongest depressor when eye is abducted
IR
why do patients tilt their head in trochlear nerve palsy?
compensate for extortion
strabismus in adults vs children
congenital/infancy in children so less cncerning
acquired in adults due to pathology/disease involving neuromuscular junctions/ nerves
eye position in CN3 palsy
abducted, depressed
ptosis, maybe dilated pupil
causes of CN3 palsy
pupil sparing
-vasculopathic e.g. DM, HTN
pupil involving
-compressive, tumour, posterior communicating artery aneurysm, raised ICP)
why would a communicating artery aneurysm involve the pupil?
parasympathetics run superficially on CN3 and aneurysm is superficial too
eye position on CN4 palsy
extorted, elevated, adducted
when is diplopia worst with CN4 palsy? why?
looking down medially e.g. stairs, reading
cant get eyeball to look down due to loss of SO
causes of CN4 palsy
-vasculitic (DM, HTN)
-trauma
-congential
-tumour
eye position in CN6 palsy
adducted
causes of CN6 palsy
-DM, HTN
-raised ICP
worst diplopia with CN6 palsy
horisontal gaze
