Relative afferent pupillary defect: role and assessment

Relative afferent pupillary defect (RAPD) is one of the more important clinical signs in neuro-ophthalmic examination. Quite often its presence is the only objective sign of unilateral or asymmetric dysfunction of the optic nerve. Hence, its detection plays a critical role in making a diagnosis of retrobulbar optic nerve pathology where examination at the slit lamp may not show any abnormality of the ocular media, retina or optic nerve head.