Statistical analysis
Continuous variables were summarized as mean with standard deviation and median with interquartile range. Categorical data were expressed with frequency and percentage. Differences across the groups in baseline characteristics were evaluated by the Kruskal-Wallis test.A generalized linear mixed model (GLMM) was applied to evaluate the treatment effect on SER, AL and VA. The model included treatment and the interaction time by treatment as fixed effect, age and baseline value as fixed covariate; and subject and eye (right or left) as random effect. Multiple comparisons were adjusted using sequential Bonferroni. Two-sided p-values of less than 0.05 were considered statistically significant. IBM SPSS Statistics V.24.0 (IBM Corp. Released 2016, Armonk, New York, USA: IBM Corp), was used for statistical analysis.