Anatomy: the orbit and the eye Flashcards
what are the 3 layers of the eye
outer fibrous layer, middle uvea layer (vascular), retinal photosensitive inner layer
what is in the fibrous layer of the eye
sclera and cornea
what is in the middle layer of the eye (uvea)
iris, ciliary body and choroid
what is in the inner layer of the eye (retina)
optic disc, macula, fovea
what is the anterior segment of the eye divided into and where is it
in front of the lens: anterior chamber between the cornea and iris/ posterior chamber: between iris and suspensory ligaments
where is the posterior segment of the eye and what does it contain
behind the lens - 2/3rds of the eye, contains vitreous body
what part of the eye secrete aqueous in the posterior chamber
smooth muscle and blood vessels of ciliary body
where does aqueous circulate and what is it’s function
circulates in posterior chamber and nourishes lens, then passes through pupil to anterior chamber and nourishes cornea
where is aqueous reabsorbed to
scleral venous sinus at iridocorneal angle (bottom of iris and sclera - glaucoma open vs closed angle)
describe the arterial blood supply to they eye
internal carotid –> opthalmic artery –> ciliary arteries
what is an end artery
an artery with insufficient anastomoses to maintain viability of tissue if occluded
what is the arterial/ venous supply to the retina and what type of artery/ vein are they
central artery/ vein of the retina - they are end arteries/ veins
what 3 veins does the eye orbit blood drain into? why is this known as the danger triangle)
superior ophthalmic vein, inferior ophthalmic vein and facial vein (anteriorly) - big circle of veins
what is the fundus of the retina and what 3 features does it contain
posterior area where light is focused: optic disc, macula and fovea
what does the optic disc contain and what does it cause in vision
CN II and only point of entry/ exit for blood vessels
what part of the eye has the greatest density of cones
macula
what part of the eye has the most accurate vision and where is it
fovea - centre of the macula
what is the pathway light follows directly after it has hit the retina
(posterior –> ant) photoreceptors –> ganglion cells –> axons –> afferent optic nerves
what can occlusion of a retinal vein/ artery branch lead to
ischeamia and loss of vision in a field
what can occlusion of a retinal vein/ end artery lead to
monocular blindness (whole eye)
how does light reach the occipital lobe from the retina
retina –> optic nerve –> optic chiasm –> optic tract –> lateral geniculate nucleus –> primary visual cortex in occipital lobe
what 6 bones make up the eye orbit
orbital plate of ethmoid, orbital plate of maxilla, sphenoid, frontal bone, zygomatic, lacrimal
which bones are most easily fractured in the orbit
plate of ethmoid and maxilla (posterior and inferior) - blowout fracture
where is the supraorbital notch/ foramen and what is it for
frontal bone - for supraorbital nerve and ophthalmic CNV
where is the infraorbital foramen and what is it for
maxilla - for infraorbital neurovascular bundle
what muscle surrounds the eye and what is it’s innervation
orbicularis oculi - CNVII
what is the only muscle responsible for raising the upper eyelid, what type of muscle is it and what is it’s innervation
levator palpebrae superioris - skeletal muscle (CN III)
what muscle helps to keep the superior eyelid open, what type of muscle is it and what is it’s innervation
superior tarsus muscle AKA muller’s muscle - smooth muscle - sympathetic control
where and what are tarsal./ meibomian glands
line the eyelids - produce oil that stops eyes tear film evaporating
what is the function of the lacrimal gland, where is it and where does it drain to
secretes and aqueous tear film for the eye - washes over eye, drains into lacrimal sac (inferior and medial) then drains into nasolacrimal duct (nose)
where is the lacrimal gland and what is it’s innervation
superolateral in frontal bone - lacrimal nerve which is a branch of the ophthalmic trigeminal nerve (CNV1)
what are the 3 axis of eye movement of the eye and what do they do
vertical axis (left and right - abduct and adduct) / transverse axis (up and down - elevation and depression) / anteroposterior (intorsion and extorsion)
name all the extraocular muscles and the 2 that dont have secondary movement
superior and inferior rectus, medial and lateral rectus (o secondary movement), superior and inferior oblique, (levator palpebra superiossis - eyelid)
what innervation do the extraocular muscles have
lateral rectus CNVI (abducens), superior oblique CNIV (trochlear) and all others CNIII (occulomotor)
what are the functions of the lateral and medial rectus
lateral abducts only to bring in line with the orbit - medial adducts to bring in line with superior oblique
what position must the eye be in for superior and inferior rectus to elevate and depress the eye
abduction (lateral rectus)
what position must the eye be in for superior and inferior oblique to depress and elevate the eye
adduction (medial rectus) - SO causes depression and IO causes elevation
what does the superior oblique pass through to attach to the eye
trochlear loop of connective tissue
where do all the rectus muscles attach from and ro
common tendonous ring/ annulus –> sclera
where do the SO and IO attach from and to
SO from sphenoid –> sclera and IO from maxilla –> sclera
what muscles are involved in pure elevation and depression of the eye
elevation: SR and IO / depression: IR and SO
what way does the orbit face vs the eyes themself
orbit looks slightly laterally while eye looks straight ahead
