From a statistical point of view, Drs Sueke and Chandna are completely correct about their conclusions. However, Horner syndrome is a rare and life-threatening disease, so we need a more precise and easier way to diagnose it from the ophthalmologic point of view. Many factors caused Drs Sueke and Chandna’s results, including some limitations that we have reported (small sample size, no cutoff point in light intensity, etc.). The main reason is that apraclonidine results in a reversal of anisocoria, which causes the mean difference in pupil size not to be statistically significant between light and dark illumination.

We mentioned the possible side effects of using apraclonidine in children in our article. However, during our study, we only observed 2 children with conjunctival hyperemia, but no adverse systemic effects. However, as we mentioned and as Drs Sueke and Chandna suggest, a large prospective study is required to establish the safety of apraclonidine in the diagnosis of Horner syndrome in children.

We still believe that the reversal of anisocoria is easily detected clinically with the naked eye by using apraclonidine.