vision

Question 1

what does pupil do

Answer 1

regulates light input to eye

Question 2

what happens to pupil in light, how and why

Answer 2

constricts by PSNS oculomotor nerve; decreases spherical abberations and glare and increases depth of field; reduces bleaching of photo-pigments

Question 3

what happens to pupil in dark, how and why

Answer 3

dilates by SNS oculomotor nerve; increases light sensitivity in dark by allowing more light in

Question 4

diagram of pupillary reflex

Answer 4

slide 9

Question 5

pupillary reflex: afferent pathway

Answer 5

rod and cone photoreceptors synapse on bipolar cells -> synapse on ganglion cells -> pupil-specific ganglion cells exit at posterior 1/3 of optic tract -> enter lateral geniculate nucleus -> synapse at brainstem (afferent pathway from each eye synapses on Edinger-Westphal nuclei on both sides of brainstem)

Question 6

pupillary reflex: efferent pathway

Answer 6

Edinger-Westphal nucleus -> oculomotor nerve efferent -> synapses at ciliary ganglion -> short posterior ciliary nerve -> pupillary sphincter

Question 7

define direct light reflex

Answer 7

constriction of pupil of light-stimulated eye

Question 8

define consensual light reflex

Answer 8

constriction of pupil of fellow (other) eye

Question 9

neurological basis of direct and consensual reflex

Answer 9

afferent pathway on either side alone will stimulate efferent pathway on both sides

Question 10

diagram of direct vs consensual reflex

Answer 10

slide 10

Question 11

effect of right afferent defect e.g. damage to optic nerve

Answer 11

no pupil constriction in both eyes when right eye stimulated with light; normal constriction in both eyes when left eye stimulated with light

Question 12

effect of right efferent (pupil constriction) defect e.g. damage to right oculomotor nerve

Answer 12

no right pupil constriction whether right or left eye stimulated; left pupil constricts whether right or left eye stimulated

Question 13

effect of unilateral afferent defect

Answer 13

different response depending on which eye stimulated

Question 14

effect of unilateral efferent defect

Answer 14

same unequal response between left and right eye irrespective which eye is stimulated

Question 15

what does swinging torch test for

Answer 15

relative afferent pupillary defect (alternating stimulation of right and left eye with light)

Question 16

what happens in swinging torch test when damaged eye is stimulated

Answer 16

partial pupillary response still present

Question 17

what happens in swinging torch test when light swings to undamaged side

Answer 17

both pupils constrict

Question 18

what happens in swinging torch test when light swings to damaged side

Answer 18

both pupils paradoxically dilate