Eye & Orbit Flashcards
what passes through the inferior orbital fissure
inferior ophthalmic vein, infraorbital vein/artery/nerve
where is the optic chiasm in relation to the pituitary gland
superior and anterior to the pituitary
if there is injury affecting the optic nerve on one side
sight to that eye is lost, other eye works fine
if there is an issue with the optic chiasm
fibres cross over here so lateral side of each visual field is lost if information can no longer pass across the chiasm and we end up with tunnel vision
if there is a lesion in the optic tract on LHS
parts of visual field supplied by this tract will not work i.e. medial side on affected side and lateral side on RHS and this is another form hemianopia
action of orbicularis oculi
palpebral part - blinking reflex (involuntary)
orbital part - scrunching of eye (voluntary)
where is the lacrimal glad found in the orbit
upper lateral corner
drainage of tears
tears drain via puncta to canaliculi to lacrimal sac to nasolacrimal duct and then to inferior nasal meatus
parasympathetic supply of the lacrimal gland
- preganglionic parasympathetic fibres from facial nerve CN VII intermediate nerve
- travel in greater petrosal nerve & nerve of pterygoid canal
- arrive in pterygopalatine ganglion
- postganglionic parasympathetic fibres hitch-hike to zygomatic branch of CN V2 and then join the lacrimal nerve (branch of CN V1) to reach the lacrimal gland
name the 7 extra ocular muscles
4 rectus muscles - superior, inferior, middle, lateral
2 obliques - superior, inferior
levator palpebrae superioris
which extraocular muscles are not innervated by CN III
SO4 and LR6 i.e. superior oblique = CN IV and lateral rectus = CN VI
levator palpebrae superioris
found at very top of eyeball, responsible for superior eyelid movement, CN III
superior oblique
slightly medial to LPS & superior rectus, depresses and abducts eyeball (down and out), CN IV
inferior oblique
at bottom of eyeball, elevates and abducts (up and out), CN III
superior rectus
directly below LPS so sometimes difficult to distinguish between the two, elevates and adducts (up and in), CN III
middle rectus
on side of eyeball towards nose, adducts (in), CN III
lateral rectus
on side of eyeball towards exterior skull, abducts (out), CN VI
inferior rectus
very bottom of eyeball, depresses and adducts (down and in), CN III
injury of CN III can lead to paralysis of
superior/middle/inferior rectus, inferior oblique and levator palpebrae superioris
effect on eye of injury to CN III
removes parasympathetic pupil constriction leading to dilated pupil (mydriasis) with ptosis (complete loss of levator palpebrae superioris) so eye is turned downwards and inwards as superior oblique and lateral rectus are still intact
describe the layers of the eye
sclera = outermost fibrous layer
choroid = vascular layer
retina = innermost layer
to see far away
ciliary muscles relaxed, suspensory ligaments tense, lens is thin for distance
to see close up
ciliary muscles tense, suspensory ligaments slack, lens is thick and rounded for close up
dilator pupillae
under sympathetic control (for dim light, dilated pupil)
sphincter pupillae
under parasympathetic control (for bright light, constricted pupil)
