On day 28 , mean diurnal IOP was 20.1 , 20.0 , and 18.7 mmHg in the AR-13324 0.01 % , 0.02 % , and latanoprost groups , respectively , representing a decrease from unmedicated baseline of 5.5 , 5.7 , and 6.8 mmHg ( P < 0.001 ) .