<qa>  What is the Observation Period of the placebo?All subjects who meet the studys enrollment criteria following Screening will undergo washout of all prohibited medications, including their routine glaucoma medications. During the Placebo Run-In Period, placebo is administered twice daily to both eyes in all subjects. During the Treatment Period, study drug is applied to both eyes for a total of 12 weeks followed by an Observation Period of approximately 7 days wherein no study eye drops are instilled. 