12. Functional Anatomy And Disorders Of The Eye Flashcards
What 3 openings are found at the apex of the orbital cavity?
Superior orbital fissure.
Inferior orbital fissure.
Optic canal.
What anatomical relation means the inferior and medial walls of the orbital cavity are weaker and also means infection can spread here?
Ethmoid sinuses found medially, and maxillary sinus found inferiorly.
What causes an orbital blow out fracture?
Sudden increase in intra-orbital pressure, such as from retropulsion of the eye ball by fist or ball, fractures the floor of the orbit.
Where can the orbital contents and blood prolapse into in an orbital blow out fracture?
The maxillary sinus.
Why might someone with a blo out fracture be unable to look up?
Fracture site can trap structures, in this case the extra orbital muscle located near the floor or orbit.
Why may a patient with an orbital blow out fracture experience anaesthesia over the affected check on the affected side?
Infraorbital branch of the maxillary division of the trigeminal nerve runs through the base of the eye, and so is damaged, leading to reduced sensation in upper teeth and gums.
What sign is seen on a X-ray if tissue has prolapsed into the maxillary sinus in an orbital blow out fracture?
Tear drop sign.
What does the orbital cavity contain?
Lacrimal apparatus. Nerves and blood vessels. Orbital fat. Globe of the eye and its internal structures. Extra-ocular muscles.
What is the function of the tarsal plates of the eyelids?
Provide a connective tissue skeleton to the eyelid for firmness and shape.
What is the orbital septum?
A thin sheet of fibrous tissue originating from the orbital rim which blends with the tendon of levator palpebrae superioris and tarsal plates.
What structures does the orbital septum separate? What advantages does this provide?
Intra-orbital contents from eyelid fat and orbicularis oculi muscle.
Acts as a barrier against infection spreading from the pre-septal space to post-septal (orbital cavity proper).
Name 2 causes of periorbital cellulitis
Secondary to infection from bites, periorbital trauma, sinuses (fronto-ethmoidal).
How would you tell if a periorbital cellulitis is pre-septal or post-septal?
Pre-septal - swelling is localised.
Post-septal - swelling more diffuse.
Give 2 complications of periorbital cellulitis
Abscess formation.
Spread of infection intracranially via veins of orbit draining to cavernous sinus, pterygoid venous plexus and facial veins, leading to a cavernous sinus thrombosis.
What is the role of Meibomian glands?
Glands inside tarsal plates - secrete oily substance onto edge of eyelashes, when blink rubs over front of eye and stops tears from evaporating and dripping over the edge of the eyelid.
What is a Meibomian cyst?
Blockage of the Meibomian glands by the oily substance they secrete, causing a painless cyst.
What is a stye?
Glands of Zeis blocked due to staph infection, causing a painful lump.
What is blepharitis?
Inflammation of the whole base of the lashes. Can affect the Meibomian glands.
What is conjunctivae?
Transparent secretory mucosa producing mucous and tears lubricating the conjunctival and corneal surfaces of the eye. Highly vascular with small blood vessels within the membrane. Lacrimal apparatus also involved in secretion of tears into the conjunctival sac.
What 3 structures make up the lacrimal apparatus?
Lacrimal gland.
Lacrimal sac.
Nasolacrimal duct.
What is the function of blinking?
Washes tear film across the front of the eye, rinsing and lubricating the conjunctivae and cornea.
What parts of the eye does the conjunctiva cover?
Sclera, inside of eyelids (forming a conjunctival sac), does not cover cornea.
What is conjunctivitis?
Inflammed and infected conjunctiva.
What is a subconjunctival haemorrhage?
Haemorrhage from a blood vessel in the conjunctiva.
