Purpose The aim of this study was to investigate the effect of overnight orthokeratology (OOK) on ocular surface and meibomian gland dysfunction in teenagers with myopia. Methods A total of 59 subjects were recruited in this prospective study. The following tests were performed before and after 1, 3, 6, 12, and 24 months of OOK lens wear, including ocular surface disease index (OSDI) questionnaire, slit-lamp examination, and Keratograph 5M. Results No infectious keratitis occurred during the study. OSDI scores increased gradually and reached the maximum at 6 months of OOK wear (P < 0.001). The meniscus height was significantly increased at 1 and 3 months after the initiation of OOK (P=0.006, P=0.035). The corneal fluorescein staining at 1, 3, 6, 12, and 24 months after wearing OOK were all increased than the prewearing level with significant difference (P=0.014, P=0.036, P < 0.001, P < 0.001, and P=0.008, respectively). The first and the average tear film NIKBUT were all higher than the prewearing level, but there was no significant difference between every follow-up time points (P > 0.05). The lid margin abnormalities were significantly increased (P=0.003, P=0.038, and P=0.015) at 6, 12, and 24 months after the initiation of OOK. There was no significant difference in the meibomian gland orifice scores at each follow-up time points compared to the prewearing level (P > 0.05). The meibomian gland lipid secretion scores after wearing OOK were higher than those of the prewearing level, however, without statistically significant difference (P > 0.05). No significant differences of the degree of difficulty of lipid excretions were detected after the initiation of OOK (P > 0.05). There was no significant difference in meibomian gland dropout scores between all follow-up time points and the prewearing level (P=1.000). Conclusion OOK increased the symptoms of dry eye and decreased the function of tear film by affecting the meniscus height and BUT. OOK did not affect the function of meibomian glands.Clinical Study registration number: ChiCTR18000185708.

Purpose. To analyze tear function outcomes following collagen cross-linking (CXL) treatment in ectatic corneas. Methods. Fifty-seven eyes of 34 patients were included, and patients with keratoconus who underwent epithelium-on (epi-on) or epithelium-off (epi-off) CXL were evaluated. The following tests were performed preoperatively and at 1, 3, 6, and 12 months postoperatively: best-corrected visual acuity (BCVA), maximum keratometry value (Kmax), ocular surface disease index (OSDI) questionnaire, slit-lamp examination, tear meniscus height, first noninvasive Keratograph breakup time (1st NIKBUT), average NIKBUT, and bulbar redness. Results. BCVA improved in both epi-on and epi-off groups at most follow-up points, but was not significantly different between groups. At 12-month follow-up, Kmax in the epi-on and epi-off groups improved after CXL, but there was no significant difference between the groups. The OSDI in both groups decreased after operation compared with before surgery, and there was no significant difference between the two groups. Comparing the two groups, only the change in the tear meniscus height at 6 months postoperatively was statistically significant, and the pre- and postoperative values of the two groups were within the normal range (>0.20 mm). The change was small and had no clinical significance. There was no change in the 1st NIKBUT and average NIKBUT between the epi-on and epi-off groups. A change in bulbar redness was significantly better in the epi-off group than in the epi-on group at 3 months postoperatively. Comparing the effects at 1 year postoperatively, both groups had positive results in OSDI, NIKBUT, tear meniscus height, and bulbar redness. Conclusion. Both epi-on and epi-off CXL can control the progression of keratoconus, although epi-off CXL is more effective. Both methods have a positive effect on dry eye, which can improve the condition of the tear film and reduce dry eye symptoms in patients with keratoconus.