Comparison of Hypercapnia- And Hyperoxia-Induced Blood Flow Changes in the Retina Detected by MRI and Laser Speckle Imaging

Haiying Cheng¹, Yumei Yan¹, Yingxia Li¹, Timothy Q. Duong²

We recently reported blood-flow (BF) MRI of the rat retina at 90x90x1500-m;m resolution. We found that hyperoxia decreased blood flow relative to baseline (air) and hypercapnia increased blood flow. BF measurements of physiologic stimuli in the retina are sparse due to a lack of reliable blood flow imaging techniques to study the retina. Available data indicated that hypercapnic responses in the retina are controversial with some reporting no changes and others reported significant changes. To corroborate our MRI findings, we developed and applied a novel laser speckle imaging to measure BF in the rat retina under identical experimental conditions.