Fig. 1

Corneal staining and tear secretion of the 8 W, 1Y, and 2Y groups. a Representative images of corneal fluorescein staining. b The National Eye Institute corneal staining score was significantly higher in one-year-old (1Y) and two-year-old (2Y) mice than in eight-week-old (8 W) mice (all p < 0.01; Kruskal–Wallis test followed by Dunn’s post hoc test; n = 10, 6, and 8 for 8 W, 1Y, and 2Y mice, respectively). c Tear secretion did not change over time (all p > 0.05; Kruskal–Wallis test). However, when the level was normalized by body weight (BW), the normalized value was lower in both 1Y and 2Y groups than in the 8 W group (all p < 0.05; Kruskal–Wallis test followed by Dunn’s post hoc test; n = 15, 10, and 8 for 8 W, 1Y, and 2Y mice, respectively). ns, not significant; *p < 0.05, **p < 0.01, and ***p < 0.001. Data are presented as means ± standard error