Relative change in diurnal mean ocular perfusion pressure: a risk factor for the diagnosis of primary open-angle glaucoma.

PURPOSE To investigate diurnal change and pattern of variation in intraocular pressure (IOP) and systolic (SBP) and diastolic (DSP) blood pressures in a group with untreated primary open-angle glaucoma (uPOAG) and compare it with an age-matched, normal group. METHODS IOP, SBP, and DBP were measured in 14 patients with uPOAG and in 14 normal subjects, every hour between 7 AM and 10 PM and the mean ocular perfusion pressure (MOPP) was calculated. Mixed-effect linear models were used to analyze the repeated-measures data in which both fixed and random effects were included. The relative diurnal change was calculated as the percentage decrease from maximum. RESULTS The uPOAG group had the higher IOP (P < 0.001) and lower MOPP (P = 0.025). There was a significant diurnal change in IOP, SBP, DBP, and MOPP in both groups (P < 0.001). The pattern of diurnal variation in IOP (P = 0.137), SBP (P = 0.569), and DBP (P = 0.937) was not significantly different between groups but was significantly different for MOPP (P = 0.040). MOPP and IOP were most similar at 7 AM and 1 PM. Postprandial hypotension was significant for SBP, DBP, and MOPP (P < 0.001), but not IOP (P = 0.388) in both groups. The relative change in MOPP was larger in the uPOAG group (38% vs. 26%, P < 0.001), but the change in IOP was similar (42% vs. 41%, P = 0.786). There was a significant effect of DBP on IOP over the course of the day in the uPOAG group (P = 0.011) but not in the normal group (P = 0.733). CONCLUSIONS The relative diurnal change in IOP was similar in both uPOAG and normal subjects but MOPP showed a significant difference. MOPP significantly decreased after lunch, and was at its lowest in uPOAG at 7 AM, when IOP was at its highest. A significant association was found between diurnal DBP and IOP in uPOAG.