Pupil in clinical diagnosis. Light reflex anatomy and the afferent pupil defect.

The neuroanatomy for the light reflex has been reviewed. The importance of the semidecussation of visual pathways in the afferent portion of the system has been emphasized. The anatomy of the near synkinesis and its relation to the anatomy of the light reflex have been reviewed. The various abnormalities of sensory pupil function have been outlined. Particular stress has been placed on the value of the afferent pupil defect in the diagnosis of sensory lesions affecting the eye because of retinal or optic nerve disease. In addition, the value of the consensual pupil in the diagnosis of afferent defects has received special comment.