Afferent pathway for pupillary light reflex is: September 2007
Optic nerve
Oculomotor nerve
Trigeminal nerve
Ciliary nerve
Ans. A: Optic nerve Under normal conditions, the pupils of both eyes respond identically to a light stimulus, regardless of which eye is being stimulated. Light entering one eye produces a constriction of the pupil of that eye (the direct response), as well as a constriction of the pupil of the unstimulated eye (the consensual response). Comparing these two responses in both eyes is helpful in locating a lesion Normally, both pupils should constrict with light shone into either eye alone. On testing each reflex for each eye, several patterns are possible. Optic nerve damage on one side: - The ipsilateral direct reflex is lost (Example: when the left eye is stimulated, neither pupil constricts, as no signals reach the brain from the left eye due to its damaged optic nerve)