Reflexes of the Eye

Question 1

what is the corneal reflex

Answer 1

a blink, when something touches the cornea/sclera

Question 2

what is the function of the corneal reflex

Answer 2

to protect the eye from foreign objects or pathogens entering

Question 3

describe which nerves are involved in the sensory(afferent) limb of the corneal reflex

Answer 3

action potentials conducted from the cornea via CN V1 branches, to trigeminal ganglion , then along CN V to the pons

Question 4

describe which nerves are involved in the motor(efferent) limb of the corneal reflex

Answer 4

action potentials conducted via CN VII, to eyelid part of the orbicularis oculi

Question 5

describe the function/action of the vestibulo-ocular reflex

Answer 5

turns eye in the opposite direction to a head movement, stabilises gaze on an object during head movement

Question 6

what nerves connections are involved in the vestibulo-ocular reflex

Answer 6

CNS connections between CN VIII and CN III, IV and VI

Question 7

describe the function/action of the oculocardiac reflex

Answer 7

reflex bradycardia in response to tension on extraocular muscles or pressure on eye

Question 8

what nerve connections are involved in the oculocardiac reflex

Answer 8

CNS connections between CN V1 and CN X

Question 9

what muscle is involved in the wide eye opening reflex of the eye, and is it para or sympathetic innervation

Answer 9

levator palpebrae superioris, sympathetic innervation

Question 10

what muscles are involved in the pupillary constriction reflex, and is it para or sympathetic innervation

Answer 10

sphincter pupillae fibres, innervated by parasympathetic in bright light and “rest and digest”

Question 11

what muscles are involved in the pupillary dilation reflex, and is it para or sympathetic innervation

Answer 11

dilator pupillae fibres, innervated by sympathetic

Question 12

describe the muscles of the iris

Answer 12

sphincter pupillae fibres circulate around pupil on interior iris
dilator pupillae fibres radially arranged around external circumference of iris

Question 13

what is a mydriatic pupil and a miotic pupil

Answer 13

mydriatic pupil = non-physiologically enlarged pupil

mitotic pupil = non-physiologically constricted pupil

Question 14

what are the sensory(afferent) and motor(efferent) limbs of the pupillary light reflex

Answer 14

sensory = ipsilateral CN II
motor = bilateral via CN III

Question 15

what connects the ciliary body and the circumference of the lens

Answer 15

the suspensory ligament of lens

Question 16

describe what the ciliary body is, and what reflex it is responsible for

Answer 16

muscular and vascular, smooth muscle like a sphincter around circumference of the lens
lens accommodation reflex

Question 17

describe the lens accommodation reflex when the ciliary body relaxes

Answer 17

no parasympathetics, ligament tightens + lens flattens to focus on an object in the distance
relaxes in “far vision”

Question 18

describe the lens accommodation reflex when the ciliary body contracts

Answer 18

parasympathetic, ligament relaxes + lens becomes spherical to focus on near objects
contracts in “near vision”

Question 19

what 3 components are assessed clinically for lens accommodation reflex

Answer 19

bilateral pupillary constriction(sphincter pupillae), bilateral convergence of both eyes towards midline(medial rectus), bilateral relaxation of the lens(ciliary muscles)

Question 20

what are reflex tears(lacrimation) in response to

Answer 20

extra response to mechanical or chemical stimulation

Question 21

what are the afferent and efferent limbs of lacrimation reflex

Answer 21

afferent = CN V1 from cornea/conjunctiva
efferent = parasympathetic axons from CN VII