Effect of 0.5% apraclonidine on ptosis in Horner syndrome

To demonstrate the effect of apraclonidine on anisocoria and ptosis in Horner syndrome, one drop of 0.5% apraclonidine was instilled in both eyes of 3 patients who presented with acute Horner syndrome, and the effect on ptosis and anisocoria was documented. As reported in the literature, one drop of 0.5% apraclonidine reverses the anisocoria of Horner syndrome. In addition, 0.5% apraclonidine leads to a complete resolution of the ptosis associated with Horner syndrome, a finding reported once in the literature. Apraclonidine is a safe and readily available alternative to cocaine for the diagnosis of Horner syndrome.