PURPOSE. To determine the spatial pattern and temporal evolution of the change in retinal partial oxygen pressure (ΔPo2) associated with a murine oxygen-induced retinopathy (OIR) model of retinal neovascularization (NV). METHODS. On P7, newborn C57BL/6 mice were exposed to 75% oxygen until postnatal day (P)12, followed by recovery in room air until P17 or P34. Control mice remained in room air until P17 or P34. At P17 and P34, functional magnetic resonance imaging (MRI) and a carbogen inhalation challenge was used to measure retinal ΔPo2. Retinal avascularity, distance from the optic nerve head to the vascular edge in the peripheral retina, and NV incidence and severity were measured in retinas stained with adenosine diphosphatase (ADPase). RESULTS. In P17 and P34 controls and in P34 OIR animals, retinas were fully vascularized without evidence of NV. In P17 OIR mice, there was a large central retinal capillary-free zone (22% ± 3% of the entire retinal area, mean ± SD) and 4 clockhours (range 1-7) of retinal NV at the border of the peripheral vascular and central acapillary retina in 100% (36/36) of the mice. In P17 air mice, retinal ΔPo 2 over the vascularized far peripheral retina was not significantly (P > 0.05) different from the P17 control but was supernormal (P < 0.05) over the central capillary-free retina. However, no differences (P > 0.05) in retinal ΔPo2 were found between the P34 control and OIR groups. CONCLUSIONS. A reversible supernormal ΔPo2 was found only over the central acapillary retina during the appearance of retinal NV in a mouse OIR model. The present data show the applicability of carbogen-challenge functional MRI to the study of retinal ΔPo2 in vivo in eyes that are too small for the use of existing techniques.
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