OP1 - orbit & eye Flashcards
what are the 7 bones that make up orbital cavity?
- frontal bone (superiorly)
- zygomatic bone (laterally)
- maxilla (inferomedially)
- sphenoid bone
- ethmoid bone
- lacrimal bone
- palatine bone
what are the orbital plates?
they are flat smooth areas in orbital cavity = they are susceptible to fractures
- you get maxilla, frontal & ethmoidal orbital plates
where in orbit is superior orbital fissure? what passes through there?
it’s between greater & lesser sphenoid - CN III, IV, VI passes through
what is supraorbital notch?
it’s at superior lateral bit of orbit - neurovascular bundle here
what is blowout fracture?
when trauma to orbital rim but outside bit strong so fractures inner fragile bits
what is tarsus?
it’s fibrous skeleton deeper layer of eyelid = prevents infection spread
what is sclera?
white bit of eye
what is iris?
coloured bit around pupil
what is cornea?
bit that covers iris & pupil (it has 2/3 refractive power - means focuses light)
what is conjunctiva?
bit that covers sclera (white bit)
what is corneoscleral junction?
area where sclera & corneus meet = makes grey translucent circle
- also called limbus
what are the layers of eye?
- outer fibrous layer (sclera & cornea)
- uvea vascular layer (iris, ciliary body, choroid)
- retina (inner layer)
what is ciliary body?
- it’s in middle layer of eye - it’s sphincter around iris that has attachment to lens controlling shape of lens
- also secretes aqueous humour = given to lens to nourish then passes through pupil to anterior chamber so nourishes cornea too
- this fluid reabsorbed by scleral venous plexus & canal of schlemm
what is choroid?
dense vascular middle layer of eye -full of blood vessels (it’s the bit that red in photo)
what is anterior & posterior segment of eye?
anterior = in front of lens (splits again into anterior & posterior chamber). contains aqueous humour
posterior = behind lens. contains vitreous body that has vitreous humour
what is iridocorneal angle?
bit where iris & corneal meet (clinically important)
what can cause increase in intraocular pressure? (something to do with ciliary body)
ciliary body is part that makes aqueous humour - can be increased pressure if either
1. too much fluid made
2. not enough fluid absorbed (by scleral venous plexus & canal of schlemm)
what is arterial supply to eye?
internal carotid gives off ophthalmic artery
- ciliary arteries is branch of ophthalmic that supplies choroid (red bit in photo)
- central artery of retina is also branch that is an end artery
what is danger triangle of face?
bit of upper lip & nose = where facial nerve runs = means if infection in triangle then can drain to facial vein and get carried to cavernous sinus and spread infection deep
what is back of retina called?
fundus
what part of retina has no photo receptors? what does this mean?
optic disc has no photoreceptors - means that it’s a blind spot
what is macula?
area that has greatest density of cones (photoreceptor) - has depression at centre called fovea that has most acute vision since the most cones
what is the process of light absorption in retina?
light goes through & strikes retina - hits photoreceptors - passes into ganglion & synapses onto axons that form optic nerve
what is the yellow circle seen on fundoscopy?
it’s the optic disc - can see central artery & vein coming in at optic disc
what is visual pathway?
any light from right seen on left of eyeball & vice versa
- light hits both eyes (right visual field hits temporal retina on left eye & nasal retina on right eye)
- info from both right & left visual fields travel back on optic nerve
- in optic chiasm the info from nasal retina swaps sides (temporal retina info stay same side)
what is movement of eyeball in each axis:
a) transverse
b) vertical
c) anteroposterior
a) up or down
b) right or left (abduction or adduction)
c) extorsion (outwards) or intorsion (inwards)
where is lacrimal gland?
superolaterally of orbit
what is process of tear production from lacrimal glands?
CN VII stimulates lacrimal glands (parasympathetic) - fluid washed down & pushed towards medial angle w every blink - fluid collects in lacrimal lake - pass into canaliculi through puncta and moves to lacrimal sac & nasolacrimal duct (why runny nose when cry)
what are the 7 extra ocular muscles?
4 rectus (straight) muscles = superior, inferior, lateral, medial
2 oblique = superior & inferior
levator palpebrae superioris
where do rectus extraocular muscles attach from?
attach from annulus ring and insert onto sclera
what does LPS (levator palpebrae orbicularis) attach & insert onto?
attaches from lesser wing of sphenoid & attaches onto superior tarsus and skin of superior eyelid
what is mnemonicy thing for innervation of extra ocular muscles?
LR6 SO3 AO3
- lateral rectus = VI
- superior oblique = IV
- all others = III
why need to think about lots of different twisty turn of eye to find clinical tests?
because orbit axis & eyeball axis different
how to clinically test superior rectus muscle?
abduct eye (uses lateral rectus muscle to line up oblique axis) and then look up = uses superior rectus muscle to look up once abducted
how to clinically test inferior rectus?
abduct then look down
how to clinically test inferior oblique?
look towards nose (medially) then look up = tests inferior oblique since inferior oblique sort of at angle and pulls from underneath to make look up
how to clinically test superior oblique?
look medially then look down
what is meant by term yolk muscles?
when muscles work together to make movement e.g. superior rectus & inferior oblique both work to elevate eyes (but also both work against each other rotating but cancel each other out so keep straight but lift up)
