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
