Single Dose of 1% Tropicamide and 10% Phenylephrine for Pupil Dilation
Tanapat Ratanapakorn MD*, Yosanan Yospaiboon MD*, Natthira Chaisrisawadsuk MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Khon Kaen University, Khon Kaen
Objective : To compare the efficacy of pupil dilation between a single dose and three doses of 1% tropicamide
and 10% phenylephrine for binocular indirect ophthalmoscopy.
Materials and Methods : A prospective randomized double-blind clinical controlled trial was conducted. All
patients underwent the binocular indirect ophthalmoscopy and met the inclusion criteria were randomized
into two groups using block randomization. Group A received a single dose of 1% tropicamide and 10%
phenylephrine eye drops, and Group B received three doses of the same drugs. The primary outcome was the
horizontal pupil diameter measured by slit-lamp biomicroscope (Haag-Streit model 900) before and at 10, 15,
20, 25 and 30 minutes after eye drop instillation. The clinical equivalence of the efficacy of pupil dilation
between the two groups was defined as the difference of less than or equal to 1 mm (-1 mm to +1 mm).
Results : Eighty patients (160 eyes) were randomized into 40 patients (80 eyes) in group A and 40 patients (80
eyes) in group B. The mean pupil sizes at baseline of group A were 3.51 + 0.63 mm in the right eye and 3.39 +
0.67 mm in the left eye. Those in group B were 3.61 + 0.67 mm in the right eye and 3.66 + 0.72 mm in the left
eye. The mean pupil diameters at 30 minutes of group A were 7.34 + 0.51mm in the right eye and 7.41 + 0.56
mm in the left eye, whereas those of group B were 7.49 + 0.45 mm in the right eye and 7.51 + 0.40 mm in the left
eye. The mean difference of the pupil size between the two groups was 0.15mm (p = 0.175) in the right eye and
0.10mm (p = 0.362) in the left eye. The 95% confidence intervals of the difference in pupil size were -0.36 to
0.07 mm in the right eye and -0.32 to 0.12 mm in the left eye.
Conclusion : The 95% confidence interval of the difference in pupil size lay entirely within the range of
equivalence. The single dose of 1% tropicamide and 10% phenylephrine was clinically equivalent to the three
doses of the same drugs.
Keywords : Pupil dilation, Tropicamide, Phenylephrine
