Figure 6. Segmental linear analysis to analyze normalized clarity (the image contrast ratio) was plotted for each lens as a function of the BVD SEM. The results revealed that there was no linear relation between normalized clarity and the back vertex distance standard error of the mean (BVD SEM; n = 6 at all temperatures with the exception of n = 3 and n = 4 at 47.5 °C and 48 °C, respectively). All data are expressed as mean ± SEM.