The constriction of the pupils in response to light is a reflex that has long been of interest to physicians because its loss is a cardinal feature of the well known Argyll Robertson syndrome. Although an extensive literature has accumulated in the past forty years on the Argyll Robertson phenomenon, its mechanism still remains one of the unsolved problems in neurology. It is apparent that a major obstacle to an explanation of the syndrome has been the uncertainty regarding the localization in the brain stem of the pathway of the light reflex.
A dorsal view of the brain stem (fig. 7) shows some of the structures which must be taken into consideration in any discussion of this pathway. The superior and inferior colliculi of the corpora quadrigemina are situated dorsal to the cerebral aqueduct and form the roof or tectum of the midbrain. Between the superior colliculus and the
MAGOUN HW, RANSON SW. THE CENTRAL PATH OF THE LIGHT REFLEXA STUDY OF THE EFFECT OF LESIONS. Arch Ophthalmol. 1935;13(5):791-811. doi:10.1001/archopht.1935.00840050069006