UNIT 3: Eyes

Question 1

what are the three axes of movement of the eye?

Answer 1

• vertical: abduction/ adduction
• horizontal: elevation/ depression
• AP axis: medial/ lateral rotation

Question 2

what nerve innervates the superior rectus and what movements does it produce?

Answer 2

oculomotor - III

elevation/ adduction/ medial rotation

Question 3

what nerve innervates the inferior rectus and what movements does it produce?

Answer 3

oculomotor - III

depression/ adduction/ lateral rotation

Question 4

what nerve innervates the medial rectus and what movements does it produce?

Answer 4

oculomotor - III

adduction

Question 5

what nerve innervates the lateral rectus and what movements does it produce?

Answer 5

abducens - VI

abduction

Question 6

what nerve innervates the superior oblique and what movements does it produce?

Answer 6

trochlear - IV

depression/ abduction/ medial rotation

Question 7

what nerve innervates the inferior oblique and what movements does it produce?

Answer 7

oculomotor - III

elevation/ abduction/ lateral rotation

Question 8

What is the origin of the rectus muscles?

Answer 8

common tendinous ring

Question 9

what are the origins of the oblique muscles?

Answer 9

superior: body of sphenoid bone
inferior: anterior part of floor of orbit

Question 10

what movement does the levator palpulae superioris produce and what nerve innervates it?

Answer 10

elevation of upper eyelid (superior tarsal muscle also assists this movement)
innervated by oculomotor nerve has sympathetic and parasympathetic innervations

Question 11

what is the effect of oculomotor nerve palsy?

Answer 11

paralysis of muscles leads to eyelid droop (ptosis)/ non-reactive pupil/ fully dilated pupil (fully abducted/depressed)
“down and out” presentation

Question 12

what is the effect of abducens nerve palsy?

Answer 12

paralysis of lateral rectus - eye gaze - eye fully adducted (unopposed pull of medial rectus)

Question 13

which muscle closes the eyelids and what nerves innervates it?

Answer 13

orbicularis oculi - facial nerve (cranial nerve VII)

Question 14

where is the lacrimal gland found?

Answer 14

superolateral region of the orbit

Question 15

give three functions of the lacrimal gland

Answer 15

• lubrication
• nutrition and protection to ocular surface
• contains bactericidal enzymes to fight infection

Question 16

which nerve gives parasympathetic innervation to lacrimal gland?

Answer 16

facial nerve

Question 17

which nerve runs over the levator palpebrae superioris in orbit?

Answer 17

frontal nerve - ophthalmic division of trigeminal nerve

Question 18

describe the visual pathway for left and right visual fields

Answer 18

temporal fibres travel down optic nerve on ipsilateral tracts and synapse at lateral geniculate nucleus and project to primary visual cortex.
nasal fibres travel down optic nerve and DECUSSATE at optic chiasm and travel down tract to synapse onto the lateral geniculate nucleus

Question 19

describe the visual pathway for upper visual field

Answer 19

fibres in lower retina contain information about upper visual field due to refraction of the cornea. They travel along the optic nerve and tract to synapse onto the lateral geniculate nucleus. the passage of fibres is blocked by the inferior horn of the lateral ventricles so they project around it (aka meyer’s loop) and project onto primary visual cortex inferior to calcarine sulcus

Question 20

describe the visual pathway for the lower visual field

Answer 20

fibres in the upper retina contain information about the lower visual field due to refraction of the cornea. they travel along the optic nerve and tract to synapse onto the lateral geniculate nucleus. the fibres project directly to primary visual cortex, superior to calcarine sulcus

Question 21

what region of the brain is the inferior horn of the lateral ventricles and what would be the effect if there was a lesion in this region?

Answer 21

temporal lobe

lesion would cause visual deficit to upper visual field “pie in the sky”

Question 22

what is the role of the iris and what is its 2 pairs of muscles?

Answer 22

regulate size of pupil aperture - adjustment  to light
radial dilator - sympathetic innervation (long ciliary)
circular constrictor (iris sphincter) -parasympathetic innervation (short ciliary)

Question 23

describe the lens

Answer 23

held in place by suspensory ligaments attached to ciliary muscle, which has parasympathetic innervation so causes contraction ligaments slacken lens become round - close focussing

Question 24

what structures form and drain aqueous humour of the eye?

Answer 24

ciliary body: synthesises/ replenishes humour

canal of schlemn - drains humour into bloodstream

Question 25

what is the effect of increased humour?

Answer 25

higher extra-ocular pressure against rods/ cones - retinal damage loss of sight