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[Correspondence] Latanoprost for glaucoma: primum non nocere – Authors’ reply

Aharon Wegner questions the ethics of having a placebo arm, citing the tenet “primum non nocere”. It is, therefore, important to consider whether harm was likely to occur to trial participants.1 Participants were monitored much more closely than in routine clinical practice and the criterion to identify visual field deterioration was very sensitive. The median change in the visual field at the time deterioration was identified in one eye was only 1·6 dB, and the deterioration was less than 2·6 dB in 75% of participants who were identified with a change (figure 4A); figure 4B shows the change from baseline for all participants reaching the endpoint.