- OPP was calculated according to the following formula: OPP=(1/3 systolic BP + 2/3 diastolic BP) x 2/3 -IOP, diastolic OPP (DOPP)=diastolic BP-IOP. During the 4 weeks washout period, subjects will use lubricants.(Week 8) In this crossover study, with the other eye drops, the same measurement will be performed. (Week 12)