Pereira V, et al. - A randomized, double-blind, placebo-controlled add-on trial was performed to evaluate the effectiveness and safety of the combination of codeine plus acetaminophen (paracetamol) versus placebo as an add-on therapy for pain control after photorefractive keratectomy (PRK). It was concluded that the oral combination of codeine/acetaminophen was safe and significantly better than the placebo for pain control after PRK when added to the usual care therapy.