Purpose
Retinopathy of prematurity (ROP) is a potentially blinding disease with abnormal peripheral vascularization. The oxygen induced retinopathy (OIR) mouse resembles peripheral avascular ROP centrally and is more amenable to spectral domain optical coherence tomography (SDOCT). This study evaluates thickness changes of total, inner, and outer retina by SDOCT in abnormally vascularized regions of OIR mice.
Methods
Five wildtype (C57BL6/J) newborn mice pups were exposed to 75% oxygen from P7 to P12 and returned to room air (OIR), while five mice were kept at room air (control). At P17, P18, or P19, fluorescein angiography (FA) and SDOCT were performed. By FA, in each control mouse, one region was identified that displayed a uniformly dense capillary network (vascular). In each OIR mouse, hypovascular regions that had fewer capillaries and avascular regions devoid of visible capillaries were identified. Single SDOCT Bscans that transversed these regions were selected and the internal limiting membrane, outer plexiform layer, and the RPE were manually segmented. Total, inner and outer retinal thickness measurements were calculated in the vascular, hypovascular, and avascular regions over a span of 1 degree and compared using Students t-test.
Results
Total retinal thickness (mean ± standard deviation in μm) for OIR hypovascular (227 ± 19) and avascular (195 ± 13) regions was significantly lower than controls (252 ± 8, p < 0.001). Inner retinal thickness for OIR hypovascular (92 ± 27) and avascular (65 ± 10) regions was also significantly lower than controls (123 ± 7, p < 0.001). Outer retinal thickness for OIR hypovascular regions (135 ± 9) was significantly higher than OIR avascular regions (130 ± 9, p < 0.002) and controls (129 ± 3, p < 0.001). Total, inner, and outer retinal thickness measurements in OIR avascular regions were significantly lower than in OIR hypovascular regions (p<0.002).
Conclusions
OIR mice had significant inner retinal thinning in hypovascular regions and more severe thinning in avascular regions, suggesting a relationship between inner retinal thinning severity and vascular nonperfusion. Outer retinal thickening in OIR hypovascular regions may suggest edema related to abnormal vascularization. In vivo assessment of retinal thickness and vasculature in OIR mice may be useful for evaluating therapies for human ROP.
Keywords: 706 retinopathy of prematurity •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
551 imaging/image analysis: non-clinical