First Author: E.Ra JAPAN
Co Author(s): T. Iwase K. Yamamoto H. Terasaki
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To evaluate a blood flow autoregulation at optic nerve head (ONH) and choroid under hyperoxia condition using laser speckle flowgraphy (LSFG).
Nagoya University Hospital
This study comprised 15 healthy volunteers (mean age 31.2 ± 6.6). Fraction of inspired oxygen (FiO2) 40 % and then 80% was administered via a breathing mask for 10 min. The mean blur rate (MBR) of the ocular circulation at the ONH and the choroid in the subjects was assessed with LSFG (LSFG-NAVI®, softcare) before, during, and after oxygen breathing. Retinal artery vessel diameter, intraocular pressure (IOP), anterior chamber depth, axial length, retina-choroidal thickness measured by enhanced depth imaging optical coherence tomography, blood pressure and heart rate (HR) in the brachial artery were also recorded.
The mean MBR in the ONH was 47.7, 44.8, 40.6, and 47.7 before, during FiO2 40 %, FiO2 80 % and after oxygen breathing, respectively, and there was significant reduction during FiO2 80 % oxygen breathing compared to before oxygen breathing (paired t-test, P<0.001). Additionally, the retinal artery vessel diameter significantly decreased during FiO2 80 % oxygen breathing (paired t-test, P<0.001). On the other hand, the mean MBR in the choroid was 13.3, 12.5, 12.0, and 12.5 before, during FiO2 40 %, FiO2 80 % and after administration, respectively, and there was no significant difference (ANOVA, p>0.05). Also, there was no significant difference in the retinal and choroidal thickness, the anterior chamber depth, the axial length, the IOP, the HR, and systolic and diastolic blood pressure (ANOVA, p>0.05).
The mean MBR at the ONH and the retinal artery vessel diameter significantly decreased during FiO2 80 % oxygen breathing, though the mean MBR at the choroid was no significant difference in all breathing conditions as well as other factors. Our results suggested that ONH had a blood flow autoregulation under hyperoxia condition, which was different from choroid.