Five percent povidone-iodine (PI) topical application to the eye has been observed to cause apnoea under general anaesthetic (GAS). The authors designed a randomised single-blinded controlled trial to evaluate changes in respiration caused by PI eye drops. They recruited 100 patients with 1:1 allocations: 50 receiving PI and 50 receiving a balanced salt solution. Subjects were aged 2-17 years. Groups were balanced at baseline for sex, age, weight, height and preoperative measures. After eye drop instillation, treatment group, breath number, treatment group by breath number interaction and average breath duration prior to eye drop instillation were significantly changed. All significant differences occurred between the third and sixth breath following drops. The PI group had significantly longer breath duration at breaths three, four and six after drops. There was no difference for breaths one, two and seven +. Thirty of 50 in the PI group showed at least one episode of a change in respiration after drops compared to none in the control group. Median time to change in respiration was 6.9 seconds. Median duration of respiratory pause was 18.5 seconds. Patients in the PI group with history of tonsillectomy and adenoidectomy and one or bilateral myringotomies were 7.2 times more likely to have respiratory changes. Females were 2.4 times more likely to have changes. The results confirm that PI drops decrease the rate of spontaneous breathing in children with respiratory pauses of varying duration. This is not due to mechanical stimulation of eye drops causing change in respiration. A possible mechanism for effect is activation of a trigeminocardiac reflex.