eye Flashcards
What shape is the orbital cavity?
Pyramidal
What are the four walls of the orbital cavity?
Roof
Floor
Medial
Lateral
What are the three openings that transmit nerves and blood vessels in and out go the orbit?
Superior orbital fissure
Inferior orbital fissure
Optic canal
What does the orbital cavity have that protects it from injury?
Tough orbital rim
What are some important anatomical relations of the orbit?
Paranasal air sinuses
Nasal cavity
Anterior cranial fossa
What do the anatomical relations of the orbit have implications for?
Orbital trauma and spread of infection
What are the weakest parts of the orbit?
Medial and floor
What are the symptoms of orbital blow out fracture?
Perioorbital swelling, painful Double vision Impaired vision Anaesthesia over affected cheek and upper teeth and gums Cannot look upwards to
What happens in an orbital blow out fracture?
Sudden increase in intra-orbital pressure fractures floor of orbit
Orbital contents and blood can prolapse into maxillary sinus and trap structures
Who will have an orbital blow out fracture?
Trauma to front of the eye e.g. retropulsion of eye ball
Why would orbital blow out fracture cause anaesthesia over cheeks?
Infra orbital nerve may be damaged
What would you see on an X-ray of someone with a orbital blow out fracture?
One side may have a fracture and blood accumulation
Tear drop
What would you see on a CT of someone with a blow out fracture?
Grey side as has blood and orbital contents which have passed down and prolapsed
What do the eyelids do?
Protect the eye when palpebral fissure is closed
What structures does the eyelid contain?
Tarsal plates and muscles
Glands at the edge
What is the contents of the orbital cavity?
Lacrimal apparatus Nerves and blood vessels Orbital fat (lots) Globe of the eye (eyeball) and internal structures Extrinsic ocular muscles (move eyeball)
What do the tarsal plates do?
Prove a connective tissue skeleton to the eyelid
Gives firmness and shape
What is the orbital septum?
A thin sheet of fibrous tissue originating from orbital rim
What does the orbital septum blend with?
The LPS and tarsal plates
What does the orbital septum separate?
Intra-orbital contents from the eyelid fat and orbiculares oculists muscles
What does the orbital septum help to do?
Act as a barrier against infection spreading from pre septal to post petal space
What is periorybital cellulitis?
Cellulitis of orbital structures
abscess Formation and spread of infection intracranially and cause cavernous sinus thrombosis
What causes periorybital cellulitis?
Infection from bites, periorybital trauma, sinuses
Where do veins of the orbit drain?
Cavernous sinus
Pterygoid venous plexus
Facial veins
What do glands within the tarsal plate secrete?
Glands within the tarsal plate secrete oily substances to prevent evaporation of tear film and tear spillage
What happens when these glands within the tarsal plate block?
Meibomian cyst
What is a stye?
Eyelash follicles can block by infection staph
What does the conjunctivae do?
Secretory mucosa lubricating the conjunctival and corneal surfaces
Also secrete tears
What does the lacrimal apparatus do?
Secretes tears into conjunctival sac
What is the lacrimal apparatus made up of?
Lacrimal gland
Lacrimal sac
Nasolacrimal duct
What does blinking do?
Washes tear film across front of eye, rinsing and lubricating the conjunctivae and cornea
What is treatment for stye and meibomian cyst?
Hot compress
What is the conjunctiva?
Transparant mucous membrane
What does the conjunctiva cover?
White of the eye (sclera), lines inside of eyelid and does not cover cornea
How vascular is the conjunctiva?
highly vascular with small blood vessels within the membrane
What is conjunctivitis?
Inflammed and injected in infections
What is sunconjunctival haemorrhage?
Haemorrhage from blood vessels- like a bruise
Do nothing
What is the main arterial supply of the eye?
Ophthalmic artery
What is the venous drainage of the eye?
cavernous sinus, pterygoid plexus and facial vein
What is the general sensory innervation of the eye?
Trigeminal nerve
What is the special sensory innervation for vision?
Optic nerve
What motor nerves to muscles in the eye?
Occulomotor, trochlear and abducens
What maintains the eyeballs position?
Suspensory ligament
Rectus muscle
Orbital fat
What is the outer layer of the eyeball?
Fibrous layer
tough sclera
continuous anteriorly as transparent cornea
What is the middle layer of the eyeball?
Vascular consisting of choroid, ciliary body and iris
What is the inner layer of the eyeball?
Retina
inner photosensitive layer lying on an outer pigmented layer
Is there any blood vessels in the cornea?
No as needs to be see through so light can get through
what is aqueous humour secreted from?
Ciliary processes within the ciliary body
Where does the aqueous humour flow?
Posterior chamber, through pupil and anterior chamber,
Nourishes lens and cornea, drains through iridocorneal angle via trabecular meshwork into canal of schlemm
What is glaucoma?
When drainage od aqueous humour from anterior chamber is blocked
What is open angle glaucoma?
Trabecular meshwork deteriorates
chronic
What is closed angle glaucoma?
Narrowing of the iridocorneal angle
What does glaucoma cause?
Rise in intracranial pressure and damage to optic nerve by optic disc cupping
Sight threatening
What is aqueous humour for?
Provides nourishment and oxygen to lens and cornea
What is light detected by in the eye?
Retinas photoreceptors
What are generated in response to light?
Action potentials which pass via ganglion cell whose icons collect in area of optic disc to optic nerve
What needs to occur for light to focus on retina?
Transparent medium
Refraction (bending of light)
What will pathology affecting the eye cause?
transparency of structures and refraction ability
What will happen if looking at something far away?
Refracted as it passes through number of structures and fluids from outside in
How does the eye look at something close?
Pupil constricts
Eyes converge
Lens becomes more biconcave
As you get older what happens to the eye?
Lens becomes stiffer and less able to change shape
Also progressive opacities can also occur within lens e.g. cataracts
What is presbyopia?
Age related inability to focus near objects (stiffer lens)
What is the innervation of the elevator palpebrae and superior tarsal muscle?
Oculomotor
What is the action of the elevator palpebrae and superior tarsal muscle?
elevates eye
What is the consequence of damaging theelevator palpebrae and superior tarsal muscle?
Eye cant open
What is the innervation of the Palpebral part of orbicularis oculi?
Facial
What is the action of the Palpebral part of orbicularis oculi?
Closes eye
What is the consequence of damage of the Palpebral part of orbicularis oculi?
Cant close eye
What is the innervation of the extra ocular muscles?
Oculomotor
Apart from LR=Abducens and SO= trochlear
What does the lateral rectus do?
Move eye laterally
abductions
What does the medial rectus do?
Moves eye medially
Adducts
What does the superior rectus do?
Depress
Roll up and in
Intortion
What does the inferior rectus do?
Elevates
Rolls down and in
What does the inferior oblique do?
Elevates
roll up and out
Extortion
What does the superior oblique do?
Depresses
rolls down and out
Intortion
What happens if lateral rectus is damaged?
Unable to abduct eye, stays adducted
Diplopia made worse on horizontal gaze
What happens if medial rectus is damaged?
Abduction occurs
What happens if Superior oblique is damaged?
Extorted, up and in
Tilting the head slightly
Difficulty looking down and medially e.g. walking up stars and reading
What happens if superior rectus is damaged?
Elevation occurs
Roll down and out
What happens if inferior rectus is damaged?
Depression occurs
Roll up and out
What happens if inferior oblique is damaged?
Depression occurs
Roll down and in
