Eye disorders Flashcards
What causes an orbital blow-out fracture?
Direct impact to the front of the eye
How does direct impact cause an orbital blow-out fracture?
Causes backwards movement of eye
sudden increase in intra-orbital pressure
wall of orbit fractures
Which wall of the orbit is fractured in an orbital blow out fracture?
Floor of orbit
What happens to the associated structures of the eye immediately after an orbital blow-out fracture?
Prolapse into maxillary sinus
become trapped between the bone fragments
What are the symptoms and signs of an orbital blow-out fracture?
Peri-orbital swelling, pain
Double vision
Eye appears sunken
Limited upward eye movement
Anesthesia over cheek on affected side
Why does the eye appear sunken with an orbital blow-out fracture?
Due to prolapse of the associated structures of the eye into the maxillary sinus, trapped between the bony fragments
Why is there limited eye movement with an orbital blow-out fracture?
Due to inferior rectus of eye prolapsing into maxillary sinus, becoming trapped between bone fragments
can’t move
Why is there anaesthesia over the affected cheek with an orbital blow-out fracture?
Damage to infra-orbital nerve of maxillary branch of CN5 trigeminal nerve
because it runs through the floor of the orbit, emerges through the infra-orbital foramen
What investigations are done for a patient with a suspected orbital blow-out fracture?
X ray
CT scan
What can be seen on a X ray and CT scan with an orbital blow-out fracture?
Fluid which is blood in maxillary sinus
Clear fracture through floor of orbit
What is peri-orbital cellulitis?
Inflammation of the eyelid and skin around the eye
What are the causes of peri-orbital cellulitis?
Trauma
Infection
Sinusitis
What are the types of peri-orbital cellulitis?
Pre-septal
Post-septal
What is the difference between pre-septal and post-septal peri-orbital cellulitis?
Pre-septal involves tissues in front of the orbital septum
Post-septal involves tissues behind the orbital septum
Which is more severe: pre-septal or post-septal periorbital cellulitis? Why?
Post-septal peri-orbital cellulitis
because infection may spread into cranial cavity, giving cavernous sinus thrombosis
How can infection in post-septal peri-orbital cellulitis spread to the cranial cavity and cause cavernous sinus thrombosis?
Venous drainage of eye
superior and inferior opthalmic veins drain into the cavernous sinus
What causes a Mebomian cyst?
Blockage of the mebomian glands
oily secretions build up and form a cyst
What is a stye?
Blockage of glands in eyelash hair follicles
What causes a stye?
Staph. aureus infection
What are the differences between a Mebomian cyst and a stye?
Mebomian cyst isn’t caused by infection, stye is
Mebomian cyst isn’t painful, stye is
What is conjunctivits?
Inflammation of the conjunctiva
What causes conjunctivitis?
Usually a viral infection
What is a subconjunctival haemorrhage?
Rupture of one of small blood vessels supplying conjunctiva
bleeds into conjunctiva
What does a subconjunctival haemorrhage look like?
Visible bruising over the white of the eye
because the conjunctiva is transparent
What is glaucoma?
Condition of increased intra-ocular pressure
causing damage to the optic nerve
impaired vision as a result
What causes glaucoma?
Blockage of drainage of aqueous humour from the anterior and posterior chambers of the eye
What are the types of glaucoma?
Open angle
Closed angle
What is open angle glaucoma?
Trabecular meshwork degenerates
How long does open angle glaucoma take to develop?
Slowly over time
What is closed angle glaucoma?
Narrowing of irido-corneal angle
access to trabecular meshwork is blocked off
How long does closed angle glaucoma take to develop?
Acutely
What happens to the accommodation reflex with age? Why?
Poorer accommodation reflex
lens becomes stiffer, less able to change shape
What is presbyopia?
Age-related inability to focus on nearby object
What is cataracts?
Progressive opacities within the lens
What causes cataracts?
Breakdown of proteins in the lens
How do cataracts affect normal eye function?
Light rays cannot pass through lens
What is papilloedema?
Swelling of the optic disc
specifically due to raised intra-cranial pressure, not other causes
How does raised intra-cranial pressure cause papilloedema?
The optic nerve is surrounded by meningeal layers
therefore surrounded by CSF also
so increased intra-cranial pressure is transmitted to the optic nerve through this
compresses the optic nerve which causes it to swell
Is papilloedema usually unilateral or bilateral?
Bilateral because raised intra-cranial pressure will usually affect both optic nerves
What is optic disc cupping?
Increased diameter of the optic disc cup
What causes optic disc cupping?
Raised intra-ocular pressure
e.g. glaucoma
How is papilloedema different to optic disc cupping on a fundoscopy?
With papilloedema, optic disc is swollen, blurred margins
With optic disc cupping, no swelling of optic disc and well-defined margins
How does a damaged orbicularis oris muscle affect the eye?
Cannot close the eye
reduced lubrication of the eye, reduced protection of eye
Lower eyelid falls away,
pooling of tears, may cause infection
What are the consequences of stenosis of the lacrimal duct system?
Excessive tearing
Potential inflammation, infection
What are the stages in a clinical examination of the eye?
I - inspection
VA- visual acuity tests e.g. Snellen chart
F - visual field tests e.g. confrontation
R - reflexes e.g. pupllary light and accommodation
O - opthalmoscope
M - eye movements
