The average drop size produced by standard eyedrop bottle exceeds the maximal capacity that the human eye are absorb topically. This excess leads to medication waste, increased costs, and greater risk of side effects.

The Nanodropper is a commercially available, FDA listed eyedrop bottle adapter that delivers a smaller drop size. The investigators hypothesize the Nanodropper is noninferior to the standard eye drop bottle for pupil dilation.

In this study, participants have one eye randomly chosen to be dilated with the Nanodropper and the fellow eye dilated with the standard bottle with a 50/50 mixture of tropicamide 1% and phenylephrine 2.5%. Pupil size before and after 30 minutes of dilation are measured with a pupillometer and compared between fellow eyes to see if there is a difference.

Ophthalmic medications are available in eyedrop bottles that produce on average a drop size of about 40 uL, while the human eye can only hold about 7-10uL. This excess leads to medication waste, increased costs, and greater risk of side effects.

The Nanodropper is a commercially available, FDA listed (class 1 medical device, 510(k) exempt) eyedrop bottle adapter that delivers a smaller drop size of 10 uL. The investigators hypothesize the Nanodropper is noninferior to the standard eye drop bottle for pupil dilation.

This is a prospective comparative matched pairs study of adults scheduled for routine bilateral eye dilation. Exclusion criteria includes anisocoria and medications affecting pupil size. One eye is randomly dilated with the Nanodropper and the fellow eye dilated with the standard bottle with a 50/50 mixture of tropicamide 1% and phenylephrine 2.5%. Pupil size before and after 30 minutes of dilation are measured with a pupillometer and compared between fellow eyes within the same subject with a noninferiority margin of 0.5mm.

Inclusion Criteria:

• age >18 years old
• scheduled for routine bilateral eye dilation

Exclusion Criteria:

• narrow angles
• allergies to phenylephrine or tropicamide
• concurrent use of any mydriatic agents (e.g., atropine, cyclopentolate, brimonidine)
• baseline anisocoria (>1 mm)
• traumatic pupil,
• surgical pupil
• unilateral pseudoexfoliation.