Figure 1

Effect of visual manipulations on refractive (a) and axial (b) parameters. Comparisons of (a) refractive (spherical equivalent and refractive astigmatism) and (b) axial (vitreous chamber depth and axial length) parameters across four groups of birds were performed using one-way ANOVA with Bonferroni’s pairwise post-hoc tests. The level of significance is indicated as follows: *p < 0.05, comparisons between normal and treated groups (− 10 D, H-WTR and H-ATR); ^†p < 0.05, comparisons between – 10 D and the two sphero-cylindrical lenses treated groups (H-WTR and H-ATR); ^‡p < 0.05, comparisons between two sphero-cylindrical lenses treated groups (H-WTR and H-ATR). When compared to normal group, all three treatment groups were found to have significantly higher myopic errors, increased vitreous chamber depths and axial lengths. H-WTR group developed less myopic error but more refractive astigmatism when compared to – 10 D and H-ATR groups.