Iopidine®

This is the test that displaced cocaine. Denervation makes the dilator's alpha-1 receptors supersensitive, so apraclonidine dilates the affected pupil while very weakly constricting the normal one, and the anisocoria REVERSES. Across 31 eyes with oculosympathetic paresis and 54 control eyes, all confirmed against the cocaine test, apraclonidine dilated the affected pupils by a mean 2.04 mm and constricted the controls by 0.14 mm, reversed the anisocoria in every Horner case, and lifted the ptotic lid by a mean 1.75 mm. The authors concluded it has at least the sensitivity and specificity of the cocaine test. Two cautions the study does not cover: supersensitivity takes days to weeks to develop, so an acute Horner can test falsely negative, and apraclonidine is avoided in infants for the risk of central nervous system depression.