Quantitative comparison of in vivo and ex vivo meibography in BALB/c mice

Aims/Purpose: We recently introduced a new method for in vivo meibography in BALB/c mice. In this study, we compared the in vivo and ex vivo meibography in young and old mice. Methods: Eighteen male BALB/c mice (9 young mice and 9 old mice) were used in this study. We performed in vivo meibography on the upper and lower eyelids of the mice. Then, the mice were sacrificed, and the eyelids were excised en bloc . Ex vivo meibography was performed on the eyelids. For quantitative comparison, the number of meibomian glands(MG) identifiable in in vivo and ex vivo meibography was counted. For the same MG in lower eyelids of in vivo and ex vivo meibography, the horizontal length(HL), vertical length(VL), and area of the MG were measured and compared using image J. Results: The number of mean identifiable MG of in vivo and ex vivo meibography was 7.4 ± 0.8 and 11.6 ± 0.6 in upper eyelids ( p < 0.001), and 8.4 ± 0.7 and 11.8 ± 0.9 in lower eyelids ( p < 0.001), respectively. The mean HL of the same MG of in vivo and ex vivo meibography was 0.16 ± 0.03 and 0.17 ± 0.03 mm ( p = 0.001). The mean VL of the same MG of in vivo and ex vivo meibography was 0.59 ± 0.08 and 0.69 ± 0.09 mm ( p = 0.001). The mean area of the same MG of in vivo and ex vivo meibography was 0.14 ± 0.05 and 0.17 ± 0.05 mm 2 ( p = 0.001). The HL ( r = 0.929, p < 0.001), VL ( r = 0.737, p < 0.001), and area ( r = 0.777, p < 0.001) of a MG of in vivo and ex vivo showed a strong positive correlation between them. The in vivo/ex vivo ratios of HL, VL, and area was 0.92 ± 0.09, 0.82 ± 0.05, and 0.82 ± 0.23 in young mice, and 0.95 ± 0.06, 0.89 ± 0.10, and 0.82 ± 0.16 in old mice. They showed no significant difference between young and old mice ( p = 0.404, 0.102, and 0.984, respectively). Conclusions: This is the first study to compare quantitatively in vivo and ex vivo meibography in mice, the most common animal models for dry eye syndrome. In vivo meibography showed shorter HL, VL, and smaller area compared to ex vivo meibography, but there was a strong positive correlation between them. Because there was no significant difference in the in vivo/ex vivo ratio of HL, VL, and area between young and old mice, there is no problem comparing in vivo meibography between young and old mice. Reference Hwang HS et al. A novel transillumination meibography device for in vivo imaging of mouse meibomian glands. Ocul Surf. 2021 Jan;19:201–209.