The percentage of eyes in which the increase in IOP using a single postwashout IOP differed from the increase in IOP using the mean of 3 measurements by more than 1.5 mm Hg was 35.1 % , 25.6 % , 34.2 % , 30.0 % , and 31.4 % when the single measurement was made at 8 am , 12 pm , 4 pm , a randomly chosen single measure of those 3 times , and the time closest to that of the prewashout IOP , respectively .