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Response of Inner Retinal Oxygen Extraction Fraction to Light Flicker Under Normoxia and Hypoxia in Rat
摘要： PURPOSE. Oxygen extraction fraction (OEF), defined by the ratio of oxygen metabolism (MO2) to delivery (DO2), determines the level of compensation of MO2 by DO2. In the current study, we tested the hypothesis that inner retinal OEF remains unchanged during light flicker under systemic normoxia and hypoxia in rats due to the matching of MO2 and DO2. METHODS. Retinal vascular oxygen tension (PO2) measurements were obtained in 10 rats by phosphorescence lifetime imaging. Inner retinal OEF was derived from vascular PO2 based on Fick's principle. Measurements were obtained before and during light flicker under systemic normoxia and hypoxia. The effects of light flicker and systemic oxygenation on retinal vascular PO2 and OEF were determined by ANOVA. RESULTS. During light flicker, retinal venous PO2 decreased (P < 0.01, N = 10), while inner retinal OEF increased (P = 0.02). Under hypoxia, retinal arterial and venous PO2 decreased (P < 0.01), while OEF increased (P < 0.01). The interaction effect was not significant on OEF (P = 0.52), indicating the responses of OEF to light flicker were similar under normoxia and hypoxia. During light flicker, OEF increased from 0.46 ± 0.13 to 0.50 ± 0.11 under normoxia, while under hypoxia, OEF increased from 0.67 ± 0.16 to 0.74 ± 0.14. CONCLUSIONS. Inner retinal OEF increased during light flicker, indicating the relative change in DO2 is less than that in MO2 in rats under systemic normoxia and hypoxia. Inner retinal OEF is a potentially useful parameter for assessment of the relative changes of MO2 and DO2 under physiologic and pathologic conditions.
关键词： vascular oxygen tension,retina,oxygen extraction fraction,hypoxia,light flicker
更新于2025-09-23 15:22:29
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The Effects of Diabetic Retinopathy Stage and Light Flicker on Inner Retinal Oxygen Extraction Fraction
摘要： PURPOSE. We determined the effects of light ?icker and diabetic retinopathy (DR) stage on retinal vascular diameter (D), oxygen saturation (SO2), and inner retinal oxygen extraction fraction (OEF). METHODS. Subjects were categorized as nondiabetic control (NC, n ? 42), diabetic with no clinical DR (NDR; n ? 32), nonproliferative DR (NPDR; n ? 42), or proliferative DR (PDR; n ? 14). Our customized optical imaging system simultaneously measured arterial and venous D (DA, DV) and SO2 (SO2A, SO2V) before and during light ?icker. Inner retinal OEF was derived from SO2 values. Light ?icker–induced ratios of metrics (DAR, DVR, SO2AR, SO2VR, OEFR) were calculated. RESULTS. Arterial D was larger in NPDR compared to NC (P ? 0.01) and PDR (P ? 0.002), whereas DV was similar among groups (P ? 0.16). Light ?icker increased DA and DV (P (cid:2) 0.004), but DAR and DVR were similar among groups (P ? 0.09). Arterial SO2 was higher in all groups compared to NC (P (cid:2) 0.02) and higher in PDR compared to NDR and NPDR (P<0.001). Arterial SO2 did not change with light ?icker (P ? 0.1). Venous SO2 was higher in NPDR and PDR compared to NC and NDR (P (cid:2) 0.02). Light ?icker increased SO2V in NC, NDR, and PDR (P (cid:2) 0.003), and SO2VR was lower in NPDR compared to NC and NDR (P (cid:2) 0.05). Inner retinal OEF was lower in NPDR compared to NDR and PDR (P (cid:2) 0.02). Light ?icker decreased OEF (P (cid:2) 0.03), but OEFR was greater in NPDR compared to NC and NDR (P (cid:2) 0.03). CONCLUSIONS. The ?ndings of alterations in retinal D, SO2, OEF, and their light ?icker–induced responses at stages of DR may be useful to elucidate the pathophysiology of DR.
关键词： light ?icker stimulation,inner retinal oxygen extraction fraction,diabetic retinopathy,retina
更新于2025-09-23 15:19:57