Oxygen-Induced Retinopathy (OIR)

The OIR model is an acute neovascularization model wherby animals develop preretinal neovascularization following hyperoxia exposure. Rats were exposed to 75% O2 from P7 to P12 and then returned to normoxia. Age-matched rats kept in constant normoxia were used as controls. Vascular permeability in the retina (a) and iris (b) was measured at P12, P14, P16, P18, P22, P30 and P36. The Evans blue in the tissues was normalised by total protein concentration and expressed as µg of dye per mg of protein in the tissue (means ± SD, n=4 to 7). Values statistically different from the control values are indicated by *.



Although this model has been used for several years, our group is the first to demonstrate strain-dependent variances in the development of neovascularization. To induce retinal neovascularization, Brown Norway (BN) and Sprague-Dawley (SD) rats at P7 were exposed to hyperoxia (75% O2) for 5 days (P7-P12) and then returned to normoxia. Control rats were kept in normal room air. Retinal angiography with high molecular weight fluorescein and quantification of neovascularization was performed. At age P18 (6 days after the rats were returned to normoxia), retinal flat-mounts showed a significantly larger avascular area in BN rats than in SD rats (p < 0.01, n = 5).