A pre-hospital clinician is assessing a patient's pupil responses using a penlight. The right pupil constricts when light is shone in the left eye (co...

Question

A pre-hospital clinician is assessing a patient's pupil responses using a penlight. The right pupil constricts when light is shone in the left eye (consensual response) but does NOT constrict when light is shone directly in the right eye (direct response). What does this indicate?

Accepted Answer

Right afferent pupillary defect (right optic nerve or retinal pathology) - the right eye cannot detect light (damaged afferent limb via CN II) but the efferent pathway (CN III) is intact, so the right pupil constricts consensually when the left eye receives light

Answer

Right CN III palsy preventing pupil constriction

Answer

Normal pupillary response - asymmetry is expected

Answer

Left optic nerve damage

Answer

Right Horner's syndrome

uk-dipimc MCQ (SBA): Afferent Pupillary Defect - Mechanism

A pre-hospital clinician is assessing a patient's pupil responses using a penlight. The right pupil constricts when light is shone in the left eye (consensual response) but does NOT constrict when light is shone directly in the right eye (direct response). What does this indicate?