The Effect of Eyedrop Size on Pupillary Dilation Using the Nanodropper Bottle Adapter

Ophthalmic medications administered via standardized eyedrop bottles have an average drop size of 40 µL, but absorption is limited to the conjunctival sac volume of 7-10 µL. The Nanodropper is a commercially available eyedrop bottle adapter capable of consistently delivering 10 µL aliquots. We hypothesized that the Nanodropper would supply a sufficient medication dose for mydriasis that is non-inferior to the standard eyedrop bottle.

Adult patients scheduled for routine bilateral eye dilation were selected. Exclusion criteria included anisocoria, use of mydriatic agents, and unilateral pseudoexfoliation. One eye was randomly selected and dilated with the Nanodropper, and the fellow eye dilated with the standard bottle with a 50/50 mixture of 1% tropicamide and 2.5% phenylephrine. Pre- and post-dilation pupil sizes were objectively measured with a pupillometer and compared between fellow eyes with a noninferiority margin of 0.5mm.

A total of 54 patients (108 eyes, 54 pairs) were included in the study. Pre-dilation pupil sizes were similar in the Nanodropper eye compared to the fellow eye. There was no difference in post-dilation pupil size between fellow eyes with a noninferiority margin of 0.5mm (95% CI [-0.09, 0.15], p = 0.67).

This study demonstrates that small volume eye drops using the Nanodropper adapter are as efficacious as standard volume drops for mydriasis. This may provide many clinical, practical, and economic advantages such as reducing medication excess, toxicity, and material costs.

The Nanodropper is non-inferior to the standard eyedrop bottle for pupillary dilation. Small volume eyedrops may reduce medication waste and side effects and improve affordability and patient compliance.