Horner's syndrome, Pseudo-Horner's syndrome, and simple anisocoria.

This discussion reviews the common causes of Horner’s syndrome, with emphasis on case reports from the past several years. Much of the recent literature concerns the use of apraclonidine as a diagnostic test for Horner’s syndrome, possibly as an alternative for the current gold standard of cocaine eye drops. This new literature is discussed in the context of the current standards for clinical diagnosis.