Objective: To compare the effectiveness and safety of two instillation methods of combined 0.75% tropicamide and 2.5% phenylephrine at 0, 5 minutes (min) with the same combined regimen at 0,30 minutes in preterm infants.
Material and Method: A prospective, cross-over, randomized controlled trial was performed to compare 0, 5-min instillation (Method A) of combined 0.75% tropicamide and 2.5% phenylephrine with 0, 30-min instillation (Method B) of the same regimen. Forty-two preterm infants scheduled for screening retinopathy of prematurity (ROP) were randomly assigned to two groups. Group 1 was defined as preterms applied by Method A at first examination then by Method B 1 4 weeks apart whereas vice versa in Group 2. Pupil size, heart rate (HR), systolic and diastolic blood pressure (SBP, DBP) were recorded before and after eye-drop instillation.
Results: Mean time to 7-mm pupil size was no statistically significant difference between the two methods (Method A 46.47 min, Method B 46.58 min; p = 0.894). Method B has mean longer time to maintain 7-mm pupil size than Method A (Method A 67.67 min, Method B 75.33 min); but not statistically significant different (p = 0.323). HR, SBP and DBP were not significant change between the two methods.
Conclusion: Both instillation methods produced consistently sufficient mydriasis and safety for evaluation peripheral fundus. Method B has slight longer mydriatic effect than Method A; thus giving more time to evaluate infant’s eye for ophthalmologists.

Keywords: Mydriasis, Pupillary dilation, Tropicamide, Phenylephrine, Retinopathy of prematurity (ROP), Preterm infants