Efficacy of A Mydriatic Mixture of 0.5% Tropicamide and 5% Phenylephrine at Thammasat University Hospital

Abstract

Purpose: To compare the effectiveness of mydriasis between mydriatic mixtures of 0.5% tropicamide and 5% phenylephrine versus 1% tropicamide and 10% phenylephrine.

Design: Prospective randomized controlled trial

Methods: In this study, 30 Asian patients with dark irides were randomized to receive topical 1% tropicamide and 10% phenylephrine (conventional regimen), and 30 patients to receive a fixed combination of 0.5% tropicamide and 5% phenylephrine (mixed regimen). The vertical pupillary dilatation, blood pressure, and pulses were studied.

Results: Sixty patients were equally randomized into conventional and mixed regimens. For the conventional and mixed regimen groups; the mean baseline pupil diameter was 1.49 ± 0.62 mm and 1.84 ± 0.64 mm, respectively. The mean pupil diameter at 15 minutes was statistically significant difference between both groups, 3.79 ± 0.90 mm in the conventional regimen group and 4.30 ± 1.05 mm in the mixed regimen group with mean difference 0.5133 mm (95%CI 0.0076 - 1.0191, P = 0.047). Whereas the mean pupil diameter at 30, 45, and 60 minutes showed no significant difference between groups. In the first 30 minutes, the proportion of eyes that achieved 7 mm pupil size between both groups was significant difference, 36.7% in the conventional regimen group, and 63.3% mixed regimen group (P = 0.039). At 60 minutes, the proportion was 86.7% and 96.7% respectively (P = 0.353). There was no significant difference in arterial blood pressure and pulse rate between groups.

Conclusion: The mixture of 0.5% tropicamide and 5% phenylephrine showed comparable efficacy to a conventional regimen and resulted in greater pupillary dilatation within the first 15 minutes, allowing for more rapid achievement of desired mydriasis.