Purpose: To evaluate laser speckle flowgraphy (LSFG) measurements of the optic nerve head (ONH) blood flow (BF) response to hyperoxia.
Methods: This prospective study included 30 eyes of 30 healthy volunteers (mean age: 28.5 ± 4.0, male:female = 13:17). The testing protocol had three phases: in the baseline phase, subjects breathed room air; in the hyperoxic phase, they breathed pure oxygen (6 L/min) for 15 min; and in the recovery phase, they were room air for 15 min. LSFG measurements of mean blur rate (MBR), which represents ONH BF, were taken every minute. The MBR ratio in the hyperoxic and recovery phases was calculated with reference to this baseline. Clinical parameters, including systemic blood pressure, pulse rate, and saturation of pulse-oximetry oxygen (SpO2), were measured every 5 min.
Results: SpO2 increased significantly during hyperoxia (97.3 ± 1.1% to 99.3 ± 0.7%, p < 0.001). While clinical parameters were similar in hyperoxia and baseline, MBR decreased significantly after 2 min of hyperoxia (90.8 ± 12.6%, p = 0.02), stayed steady throughout hyperoxia (mean: 89.5 ± 10.8%, p range: <0.001-0.04) compared with baseline, and returned to baseline 1 min after recovery (93.7 ± 10.3%, p = 0.25). A linear regression using a third-order polynomial fitting curve analysis revealed that the time to reach minimum MBR was 7.78 min (adjusted R(2 )= 0.87).
Conclusion: LSFG could effectively assess ONH BF changes during hyperoxia.
Keywords: Hyperoxia; laser speckle flowgraphy; ocular blood flow; optic nerve head; vasoreactivity.