Session 8- Functional Anatomy of the orbit, eye and ocular muscles Flashcards
what is the orbit
a bony pyramid housing the eyeball, its muscles, nerves vessels and most of the lacrimal apparatus
which are the weakest walls of the orbit
inferior and medial making them most vulnerable to fracture
what does fracture of the orbit lead to
a sudden increase in introrbital pressure and is often the floor that fractures
what makes the medial wall stronger than the inferior wall
although it is thinner than the inferior wall the presence of the walled air cells act as buttresses and convey an added strengh to the medial wall
what becomes infected in acute sinusitis
walled ethmoidal air cells
what travels through the inferior orbital fissure
infraorbital nerve- branch of Vb
inferior opthalmic vein
what series of holes are at the apex of the orbit
optic canal
superior orbital fissure
inferior orbital fissure
what is the transparant continuation of the sclera
cornea
what does the sclera provide in terms of attachemnt
extra-ocular muscles
what thin transparent layer of the cells cover the sclera
conjunctivae
treatment of conjuctivitis
reassurance
hygeine advice
short course of chloramphenicol eye drops
what is a cause of conjuctivitis in the neonatal period
an infective organism like chlamydia picked up from the mother’s vaginal mucosa during birth
treated with erythromycin
what causes subconjuctival haemorrhage
when one of the small conjuctival blood vessels rupture and the blood escapes under the transpareny conjunctival layer
what does the choroid continue as anteriorly
cilary body and iris
what does the cilary body consist of
cilary process and muscle
function of cilary body
connects choroid and iris
what alerts you with a red eye
if it is painful as this indicates a serious underlying cause
uveitis
what is uveitis
inflammation of the choroid layer
what is the uvea
collective term for choroid, cilary process and iris
what does the outer layer o the eyeball consist of
sclera
cornea
what does the middle layer of the eueball consist of
choroid
cilary body
iris
what does the innerlayer of the retina consist of
neurosensory cell layer
pigmented epithelial cell layer
what layers are within the retina
neurosensory cell layer
pigmented epithelial cell layer
where does the pigmented epithelial layer lie
betweem the choroid and neurosensory layer of the retina
what is the role of the melanin in the pigmented epithelial cells
helps absorb scatterd light that has passed into the eye
function of neurosensory layer
area of the retina that senses light and where photoreceptors are found
what are the cones responsible for
high visual acuity and color vision
where are the cones concentrated
macula
how does the macula appear on fundoscopy
darker
lying lateral to optic disc
what is the centre of the macula called
fovea
what is present in the fovea
small area where the only photoreceptors are cones
what causes colour blindness
absence of dysfunction of one of the red green or blue cone leads
what is the function of rods
responsible for vision in low intensity ligjt and do not discern colours
where are rods abundant
peripheral parts
what is the optic disc
accumulation of retinal axons making it devoid of photoreceptors making it the blind spot
what are the three chambers of the eyeball
anterior, posterior and virteous chamber most posteriorly
what is the virteous chamber filled with
transparent, jelly like virteous humour
what are the anterior and posterior chambers filled with
transpaarent liquid called aqeuos humour
where is the anterior chamber
space between the cornea and iris
where is the posterior chamber
space between the iris and lens where the cillary body and processes are found
what is aqueous humour important for
supporting the shape of the eyeball by the pressure it exerys
provides nourishment to the lens and cornea
where does aqueous humour drain
irido-corneal angle into the canal of schlemm via a trabecular meshwork and subsequently back into venous circulation
what happens to the deainage of aqueous humor as we age
it can become obstructed which leads to a ris ein intra-ocular pressre leading to glaucoma
what is glaucoma
irreversible damahe and death of optic nerve
what is the most common type of glaucoma
open-angle glaucoma
what causes open angle glaucoma
blockage within the trabecular meshwork
why is open angle glaucoma hard to pick up
it develops painlessly and insidiously over time
what is closed angle glaucoma
when the irido-corneal angle is narrowed by the peripheral edge of the iris
access to trabecular meshwork is blocked off
rise in intraocular presuure
how does closed angle glaucoma present
sudden onset of a painful red eye blurred vision fixed sluggish semi-dilated irregular oval shaped pupil nausea vomiting eye feels hard to palpate
what muscles form the iris
spinchter and dilator pupillae which are under the control of the ANS
what supplies nutrients to the lens
aqueous humour
what is cataracts
degredation of the proteins in the lens causes it to become clouded and less transparent
how is the shape of the lens altered
contraction of the ciliary muscle under the influence of the PNS alters the tension in the suspensory ligaments
From what artery does the arteries in the optic disc arise from
Central retina,
