Retinal Spidergrams of the ONL thickness of Sprague-Dawley WT rats at different ages. Each ONL data curve is the mean of 3–5 rats, and each data point is the mean of 3 adjacent measurements; thus, the 54 ONL measurements are reduced to 18 points across the retina, 9 in each of the superior and inferior hemispheres along the vertical meridian. Error bars are omitted for clarity. Dashed lines are given for the mean ONL thickness at ages ranging from P10 to P365. The curves illustrate the normal retinal thinning with age, the symmetrical ONL thickness in the two hemispheres along the vertical meridian, and the thinning of the ONL near the periphery of the retina compared to that of the central retina.