We also evaluated the ability of SD-OCT to visualize inner retinal damage in ouabain-poisoned retinas over 2 weeks. SD-OCT measurements found a large swelling of the inner retina at 1 dpi (
Fig. 9A) that contracted by 3 dpi (
Fig. 9B) and continuously thinned over the 2 weeks (
Figs. 9C–E'). In contrast to light-damaged retinas, dot plots of optical caliper measurements found the axial thickness of the ILM to the OPL and whole retinal thickness to be significantly reduced at 3, 5, 10, and 14 dpi relative to 1 dpi (
Figs. 9F,
9G,
n = 10,
P < 0.05), but these significant differences were not seen in the ONL measurements (
Fig. 9H,
n = 10,
P > 0.5). These data are consistent with damage from low doses of ouabain affecting only the INL and GCL cells. Dot plots also distinguished damaged and undamaged retinas after 5 dpi (
Figs. 9F,
9G) because undamaged retinas had inner retinal axial lengths that did not change over time and clustered at the top of the confidence interval, whereas damaged retinas continued to decrease in thickness up to 14 dpi. We plotted the axial inner retinal length of the ouabain-injected eyes that were imaged, tracing the morphometry of individual fish over time from 1 to 14 dpi (
Fig. 9I). These data appeared to contain two groups of eyes, one that did not exhibit any change in axial length over time (
Fig. 9I, bracketed), which were likely undamaged, and those eyes that initially swelled and then had a significant decrease in the axial inner retinal length. We analyzed these data with a K-means cluster analysis for two groups (
Figs. 9I,
9J). The means of the two groups were pairwise analyzed at each time point by Tukey's highly significant difference method. The difference in mean length of the inner retina between damaged and undamaged retinas was found to be significant at 1 dpi (
n = 10,
P < 0.01), 3 dpi, 5 dpi, 10 dpi, and 14 dpi (each
n = 10,
P < 0.005). This demonstrated that SD-OCT could noninvasively distinguish between damaged and undamaged retinas within a population of fish that were equivalently treated, but exhibited a range of phenotypes. SD-OCT should therefore allow the analysis to be focused on those fish that were actually damaged or exhibit alterations in the retinal laminar organization. We subsequently excluded the undamaged retinas from the data in
Figure 9F and replotted the data for only the damaged retinas (
Fig. 9J). This confirmed the significant difference in the inner retinal thickness between 1 dpi and other time points (
n = 5,
P < 0.001), as well as the trend in further thinning of the inner retinal thickness between 3 and 14 dpi (
n = 5,
P = 0.060).