A double-blind study comparing 0.5% and 1% tropicamide for annual retinal screening in diabetic adolescents

To determine whether there is any difference between 0.5% and 1% tropicamide in ocular discomfort and mydriatic efficacy in adolescents with Type 1 diabetes.

In a double-blind study, one drop of 0.5% tropicamide was instilled in one eye and one drop of 1% instilled in the other eye of 30 subjects aged 12-18 years. Drop strengths were randomized. Pupil size was measured before instillation, at 10, 20 and 30 min. Discomfort was measured using a recognized pain scale.

Irrespective of the concentration of tropicamide used, all pupils dilated to at least 6 mm at 30 min, sufficient for successful ophthalmoscopy. Pain was significantly less when the lower concentration of tropicamide was used; pain score for the 0.5% group [median (interquartile range)] 1.0 (0-2) and 2.0 (1-3) for the 1.0% group, P = 0.009 (Wilcoxon rank test).

This minor change in practice significantly reduces the distress associated with drop instillation without compromising the clinical examination, and may thus be important in encouraging compliance at the yearly diabetic review.