QuestionSBA
QuestionChoice
This is incorrect. A lesion in the right optic nerve would result in a lack of pupil constriction in both the right and left eyes when light is shone into the right eye. However, if light is shone into the left eye, there is constriction of both eyes as the oculomotor nerves would be functioning. Additionally, there may also be ipsilateral vision loss.
10004293
c
Right optic nerve
QuestionChoice
This is incorrect. A lesion in the left optic nerve would result in a lack of pupil constriction in both the right and left eyes when light is shone into the left eye. However, if the light is shone into the right eye, there is constriction of both eyes as the oculomotor nerves would be functioning. Additionally, there may also be ipsilateral vision loss.
10004294
d
Left optic nerve
QuestionChoice
This is incorrect. The right pretectal nucleus receives an afferent from the retinal ganglion cells of the optic nerve when light is shone into the left eye. The right pretectal nucleus will then send signals to the Edinger-Westphal nucleus of both eyes which results in an efferent through the oculomotor nerve to cause pupillary constriction in both eyes via the ciliary ganglion. If the lesion was located here, neither the left nor right pupil would constrict when light is shone into the left eye. However, if the light is shone into the right eye, there is constriction of both eyes as the oculomotor nerves would be functioning.
10004292
b
Right pretectal nucleus
QuestionChoice
This is incorrect. The left pretectal nucleus receives an afferent from the retinal ganglion cells of the optic nerve when light is shone into the right eye. The left pretectal nucleus will then send signals to the Edinger-Westphal nucleus of both eyes which results in an efferent through the oculomotor nerve to cause pupillary constriction in both eyes via the ciliary ganglion. If the lesion was located here, neither the left nor right pupil would constrict when light is shone into the right eye. However, if the light is shone into the left eye, there is constriction of both eyes as the oculomotor nerves would be functioning.
10004295
e
Left pretectal nerve
QuestionChoice
This is correct. Firstly, as there is no constriction of the left pupil when light is shone in the left or the right eye, there is a lesion either in the left optic nerve or left oculomotor nerve. However, when light is shone into the left eye, there is constriction of the right pupil, indicating it is not an afferent nerve lesion. Therefore, the lesion must be located in the left oculomotor nerve, with failure to produce left pupil constriction.
10004291
a
Left oculomotor nerve
Concept
Chapter
2693
4261
Eye anatomy
Topic
141
Neurology
13405
A 49-year-old man is having his pupil reflexes assessed in A&E. When light is directed into his right eye, there is constriction of the right pupil but not the left pupil. When light is directed into his left eye, there is a contraction of the right pupil but not the left pupil.

Which structure is most likely damaged?
a