Design: Prospective, double-masked, controlled, cross-over superiority studies. Materials & methods: Eligible volunteers in two pooled Phase III trials received microdosed mydriatics. MIST-1 study subjects received fixed-combination TR-PH, phenylephrine 2.5% (PH) or tropicamide 1% (TR). MIST-2 study subjects received TR-PH or placebo. Mean change from baseline in pupil diameter was measured by digital pupillometry at 35 min postadministration. Results: Pooled efficacy analysis included 131 subjects. Compared with TR-PH, treatment group difference in 35-min change in mean pupil dilation from baseline was 0.58 mm (p < 0.0001) with TR, 3.87 mm (p < 0.0001) with PH and 4.65 mm (p < 0.0001) with placebo. Adverse events reported were infrequent, transient and mostly mild. Conclusion: TR-PH demonstrated superior pupil dilation compared with each component and placebo. TR-PH was safe & well-tolerated.