Eye Flashcards
What forms the roof of the orbit?
Frontal bone
Lesser wing of sphenoid
What forms the floor of the orbit?
Maxillary bone
Palatine bone
Zygomatic bone
What forms the medial wall of the orbit?
Lacrimal bone
Ethmoid bone
Maxillary bone
Sphenoid bone
What forms the lateral wall of the orbit?
Zygomatic bone
Greater wing of sphenoid
What forms the apex of the orbit?
Optic canal
What are the openings into the orbit?
Optic canal
Superior orbital fissure
Inferior orbital fissure
What is the arterial supply to the orbit?
Ophthalmic artery
What is the venous drainage of the orbit?
Superior ophthalmic vein
Inferior ophthalmic vein
Where does the superior ophthalmic vein drain?
Cavernous sinus
Where does the inferior ophthalmic vein drain?
Pterygoid plexus
What provides general sensory innervation to eye?
CN Va
What are the weakest parts of the orbit?
Medial wall + floor
What is an orbital blowout fracture?
Traumatic fracture of medial wall or floor of orbit
What causes an orbital blowout fracture?
Sudden increase in intra-orbital pressure often due to fist or ball hitting eye
What happens in an orbital blowout fracture?
Orbital contents can prolapse and bleed into maxillary sinus
Fracture site can ‘trap’ structures
What are the signs of an orbital blowout fracture?
Loss of upward gaze on affected size History of trauma Periorbital swelling Double vision Anaesthesia over affected cheek
What causes anaesthesia in an orbital blowout fracture?
Infraorbital branch of CNVb runs through floor of orbit
What makes up the eyelids?
Skin Subcutaneous tissue Tarsal plate Orbicularis oculi Levator palpaebrae superioris Meibomian glands Sebaceous glands - associated with eyelash follicles
What do Meibomian glands secrete?
Meibum - an oily substance that prevents the evaporation of the tear film
What do sebaceous glands secrete?
Sweat
What is caused by a blockage of a Meibomian gland?
Meibomian cyst
What is a stye?
Infection due to blockage of sebaceous gland or eyelash follicle
Where do Meibomian glands lie?
Within the tarsal plate
What is the orbital septum?
Thin sheet of fibrous tissue that originates from the orbital rim periosteum and blends with the tarsal plates
What is the role of the orbital septum?
Prevents superficial infection spreading into orbit
What is peri-orbital cellulitis?
Infection occurring within eyelid tissue - superficial to orbital septum
Where does peri-orbital cellulitis effect?
Confined to tissues superficial to orbital septum
What happens to ocular function in peri-orbital cellulitis?
Unaffected
What is orbital cellulitis?
Infection within the orbit - deep to orbital septum
What are the signs of orbital cellulitis?
Proptosis
Exophthalmos
Reduced/painful eye movements
Reduced visual acuity
What is the risk of orbital cellulitis?
Can spread intracranially - via venous system
What is proptosis?
Protrusion of the eyeball