- Study visit 1-day 1 The subject will be instructed by the study coordinator in eyelid closure. The IOP will be measured 3 times in one 5 minute period between 7:30 and 10 am using Goldmann applanation tonometry and the median IOP will be recorded (baseline IOP). The subject will be randomized to performing eyelid closure in the right or left eye for either 1 or 5 minutes. Based on the randomization, the study coordinator will instill one drop of the prostaglandin eye drop (latanoprost, travoprost, or bimatoprost) that the patient normally uses into the appropriate eye, and observe the subject perform eyelid closure in the chosen eye for either 1 or 5 minutes.