Afferent pathway for pupillary light reflex is: September 2007
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)
Optic nerve
Oculomotor nerve
Trigeminal nerve
Ciliary nerve