THE EYE Flashcards
why is the macula not in the centre of the back of the eye?
orbital cavity is laterally aligned
what is the common site of origin of the 4 rectus muscles?
Annulus of zinn
name two structures that run through the optic canal
optic nerve
ophthalmic artery
name the 6 nerves running through the superior orbital fissure…
trochlear frontal nasocilary lacrimal abducens oculomotor
where to the levator palpebrae superioris and superior oblique originate from?
lesser wing of the sphenoid
where does the inferior oblique originate?
antero-medial floor of the orbital cavity
where do all extraocular muscles insert?
into the sclera of the eyeball
yawing can be used to describe eye movement around which axis?
vertical axis
rolling can be used to describe eye movement around which axis?
sagital axis
pitching can be used to describe eye movement around which axis?
transverse axis
what is version movement of the eye?
when eyeballs move in the same direction, when lines of sight remain parallel
what is vergence movement of the eye?
where eyeballs move in opposite directions, and line of sight doesn’t remain parallel
in addition to motor fibres, what other fibre type is found, albeit as a minority, in cranial nerves 3,4, and 6?
proprioceptive fibres from extraocular muscles
what are the three components of the accommodation reflex?
vergence
change in pupil size
change in lens shape
how does contraction of the cilary muscles effect the shape of the lens?
cilary muscles contract > lens bulges > lens thickened in anterior - posterior plane > more light refracted onto retina
What is presbyopia? Why is it more common for older people to suffer from it?
Longsightedness
lens fibres continue to be laid down throughout life. Lens becomes more stiff and less bulging occurs when cilary muscles contract
how do the medial and lateral recti create co-ordinated contraction and relaxation to aid version?
interneurones of the medial longitudinal fasciculus run to/from CNIII to CNVI
what are the two eye-related signs that indicate a raised intracranial pressure?
lateral deviation of eye and diplopia
UNCAL HERNIATION
which walls of the orbital cavity are most at risk from a blow-out fracture?
Roof, floor and medial wall
