Retinal oxygen delivery and extraction in ophthalmologically healthy subjects with different blood pressure status

Purpose To compare retinal oxygen delivery (DO 2 ) and extraction (VO 2 ) in ophthalmologically healthy subjects with different blood pressure (BP) status. Methods In this case-control study, we prospectively included 93 eyes of 93 subjects (age 50-65) from a large-scale population-based Dutch cohort (n=167,000) and allocated them to four groups (low BP, normal BP [controls], treated arterial hypertension [AHT], untreated AHT). We estimated vascular calibers from fundus images and fractal dimension (FD) from optical coherence tomography angiography scans. We combined calibers, FD, BP, and intraocular pressure measurements in a proxy of total retinal blood flow (RBF), using a validated Poiseuille-based model. We measured arterial and venous oxygen saturations (S a O 2 , S v O 2 ) with a two-wavelength scanning laser ophthalmoscope. We calculated DO 2 and VO 2 from RBF, S a O 2 , and S v O 2 . We compared DO 2 and VO 2 between groups and investigated the DO 2 -VO 2 association. Results DO 2 and VO 2 were different between groups ( P =0.009, P =0.036, respectively). In post hoc analysis, the low BP group had lower DO 2 than the untreated AHT group ( P =4.9·10 -4 ), while both the low BP group and the treated AHT group had lower VO 2 than the untreated AHT group ( P =0.021, P =0.034, respectively). There was a significant DO 2 -VO 2 correlation (R obs =0.65, b obs =0.51, P =2.4·10 -12 ). After correcting for shared measurement error, the slope was no longer significant (b cor =0.19, P =0.29), while the correlation coefficient could not be calculated. Conclusions DO 2 and VO 2 were altered in ophthalmologically healthy subjects with different BP status. Future studies could elucidate whether these changes can explain the increased risk of several ophthalmic pathologies in those subjects.