Additionally, previous research on glaucoma medications has been limited to the effects ocular hypotensive drugs on 24-hour IOP or daytime aqueous humor dynamics; few studies have addressed their effect on nocturnal aqueous humor dynamics. Beta-blockers have been proven effective in lowering IOP during the day by decreasing aqueous flow10. However, limitations have been found in their IOP-lowering effect overnight11. Prostaglandins, which increase uveoscleral outflow12, seem to possess a hypotensive effect that is constant throughout the 24-hour period11. Dorzolamide reduces aqueous flow to lower IOP but few studies have addressed its effect at night13. This study is designed to elucidate the physiological mechanisms driving the efficacy of these drugs throughout the 24-hour period, i.e. circadian rhythms in aqueous humor dynamics.