Eye Flashcards
how may extra ocular muscle
6
3 pupil movements
movement of pupil after muscle action
movement of pupil during testing muscle action
position of pupil after nerve paralysis
name 6 extra ocular muscle
superior rectus
superior oblique
median rectus
inferior oblique
inferior rectus
lateral rectus
2 axis and walls of orbital cavity orientation
medial vs lateral walls
axis of orbit vs axis of eyeball
basic shape of orbit
pyramid
3 axis of movement of the eye
horizontal
vertical
torsion
3 movements of the eye
elevation/depression
abduction / adduction
intorsion / extorsion
intorsion
the top of the eye moving towards the nose
extorsion
the superior aspect of the eye moving away from the nose
vertical axis
left and right
horizontal axis
up and down
torsion axis
towards and away from the nose
intorsion and extortion
intorsion = medial rotation, incyclotorsion
extorsion = lateral rotation. excyclotorsion
abduction and adduction of the eye
abduction = away from the nose
adduction = towards the nose
elevation and depression
elevation = up
depression = down
what direction would pupil face if lateral rectus contracts
Abduction
what direction would the pupil face if the superior rectus contracts
Elevation, incyclotorsion, adduction
what direction would the pupil face if the inferior oblique contracts
excyclotorsion, elevation, abduction
what direction would the pupil face if the superior oblique contracts
incyclotorsion, depression, abduction
where is the inferior oblique muscle positioned
starts on the floor of the cavity and then wraps around the eyeball
where is the superior oblique positioned
starts on the back and runs along the medial wall
what happens to the pupil when the medial rectur contracts
adduction
what happens to the pupil when the inferior rector contracts
depression
excyclotorsion
adduction
procedure of a squint or strabismus surgical correction
detach section of eye muscle is removed
muscle is moved back or brought forward
movement of pupil during testing the muscle action
testing for the presence of extra ocular muscle is different from their actions
test for superior rectus
look laterally and up
test for inferior rectus
look laterally and down
test for lateral rectus
look laterally
test for medial rectus
look medially
test for inferior oblique
look medially and upward
test for superior oblique
look medially and downward
what nerve innervated the lateral rectus
abducent nerve (VI)
what nerve innervated the superior oblique
trochlear nerve (IV)
what nerve innervates the medial rectus, superior rectus, inferior rectus, inferior oblique
oculomotor nerve (III)
how can you work out what muscle has been paralysed
position of the pupil
by the position of the pupil - the movement that is missing is the muscle that has lost innervation.
3 eyeball layers
- fibrous layer
- vascular layer
- inner layer
what parts of the eye are in the fibrous layer
sclera and cornea
look and function of the sclera
white
maintains shape of the eyeball
what is the limbus junction
the point where the translucent sclera (anterior) meets the white sclera
what is the lamina cribrosa
a defect that allows entry of the optic nerve
bulges raised intracranial pressure
why is the sclera translucent
allows light to come in
what does the cornea look like
transparent
what is the sclera covered by
conjunctiva
what is the palpebral fissure
open space between eyelids
what are the lateral and medial commissures
the medial end of the eyelids and the lateral end of the eyelids
what is the scleral buckle
procedure used for retinal detachment
if the scleral is bigger than it should be
what is scleral icterus and how is it caused
yellow eyes
hepatic failure and jaundice
build up of bilirubin (fibrous layer)
chemical build up - liver failure
what is the tissue that lines the inside of the eyelids and covers the sclera
conjunctiva
highly vascular
what is bloodshot/red eyes
blood vessels on sclera dilate = blood vessels become visible
inflammation
what does the cornea do
allows light to pass through
60% of the optical refractive power
what are some conditions of the cornea
corneal abrasion
keratoconus
keratoconus
thinning and pointing of the cornea
affects refraction ability and tends to have double / triple
what is Fuchs endothelial dystrophy
inherited condition
progressive visual blurring
cornea dehydration important
inner cornea the endothelium pumps fluid from cornea to aq humour
endothelial cells do not replicate
water left in cornea = cloudy
number of cells shifting electrolytes and water diminish over time
eye used in forensics
longer dead = cloudier eyes = more water stuck in cornea
what is the vascular layer composed of
choroid
ciliary body
iris
iris
coloured part of the eye
where is the ciliary body located
ciliary muscle ring around the line
between iris and choroid
nerve supply of the ciliary muscle
oculomotor nerve (CN3)
action of the ciliary muscle
looking at something nearby = ciliary muscle contracts = ligaments (zonular fibres) relax = greater focusing
looking at something far away = ciliary muscle relax = more tension in suspension (zonular fibres) ligaments = flatter/longer shape
cataract surgery
the inside of the diseased lens is scooped out
using phacoemulsification (Ultrasound)
replaces with new lens
parasympathetic action of iris muscle
parasympathetic stimulation causes circular muscle to contract
pupil gets smaller
sympathetic action of the iris
sympathetic stimulation causes radial muscle to contract
pupil widens
dual innervation of the iris
parasympathetic and sympathetic innervation
what is Horners syndrome
pre or post ganglionic sympathetic Nerone damage
causes mitosis ( constricted pupil)
hoe do drugs for dilating pupils work
- mydriatic medications
- tropic amide and atropine (parasympathetic antagonist)
- give the opthalmogist a better view of the retina and optic nerve
- contracts the radial pupil smooth muscle - makes pupil bigger
where do axons exit the eyeball
optic disc
optic disc
blind spot
void of rods and cones
macula
sits behind the lens
an area of retina with high cone density
parafovea
a region in the retina that circumscribes the parafovea and fovea and is a part of the macula lutea.
fovea centralis
small depression
minimised bouncing of light
ora serratus
most anterior limit of the retina
when examining a patient using lighted ophthalmoscope where is the macula and optic disc
macula = dead centre
optic disc =right edge
rods detect
black and white / shades
cones detect
colour
optic nerve diamater
4mm
age related macular degeneration is
centre vision becomes blurry and eventually black
retinitis pigments
damage on the periphery
centre bit only
fluids in the eye
aqueous humour (anterior)
vitreous humour (posterior)
vitreous humour
hyaloid canal
embryological remnant
hyaloid canal
jelly like substance
what are eye floaters
pieces of vitreous humour that had broken off
colourless - worms or hair
tiliting head - move out the way
surgery = vitrectomy procedure
aqueous humour
high turn over
fluid in posterior chamber
travels anteriorly between lens and iris
build up of aqueous humour causes glaucoma
glaucoma
build up of pressure
insufficient drainage of canals of schlep then veins
iridocorneal angle could narrow
treatment of glaucoma
drugs improving the Flow at the canal of schelm (drugs similar to prostaglandins)
decreasing aq humour production (beta adrenergic receptor antagonists)
vasoconstriction of arteries of the ciliary body (epinephrine)
insertion of glaucoma drainage implants
function of hyaloid canal
passage of the vitreous humour
