The influence of drop size on pupil dilatation.

The clinical efficacy of reduced size dilating drops (micro drops), was assessed in 60 patients. For each patient, one eye received the standard 'minim' drop size (26 microliters) while the fellow eye received a micro drop of five microliters. In 20 patients tropicamide 1% was followed after two minutes by phenylephrine 10%, another 20 patients were given tropicamide 1% alone, and for the last 20 patients, 0.5% tropicamide was used. Satisfactory mydriasis was achieved for all pupils except those receiving micro drops of tropicamide 0.5% (25 micrograms tropicamide). Tropicamide 1% in micro drop formulation (50 micrograms tropicamide) gave almost identical mydriasis to that from standard drops (containing 250 micrograms tropicamide). Tropicamide 1% in combination with phenylephrine 10% was superior to tropicamide 1% alone, after standard or micro drop administration. The micro drops used in this study were effective, easy to administer, and caused less patient discomfort.