Statistical Analysis
dry eye symptoms
REGRESSION
Continuous measures were summarized using as mean ± standard deviation (SD). Comparisons between treatment and placebo groups for eye-specific tear osmolarity and comparisons of DED severity scores of symptoms and signs among osmolarity groups were performed using generalized linear regression models with application of generalized estimating equations to account for the correlation between measures for eyes of the same patient. For eye-level analysis of association between osmolarity and signs, osmolarity groups were defined by eye-level osmolarity (≤308, >308 to ≤316, >316 mOsm/L). For person-level analysis of osmolarity with dry eye symptoms and signs, person-level osmolarity groups were based on osmolarity abnormality (defined osmolarity >308 mOsm/L or intereye difference >8 mOsm/L) and the maximum tear osmolarity from two eyes of a patient (≤308, >308 to ≤316, >316 mOsm/L). For these evaluations of associations between osmolarity and DED signs and symptoms, we performed the statistical analysis for the combined data from all three time points (baseline, six months, and 12 months) to increase the statistical power. In these analyses, time was modelled as a categorical variable, and the correlation from repeated measures at three different time points were accounted for by using the generalized estimating equations. Separate analysis for baseline, six months, and 12 months was also performed to check the consistency of the findings over time. The correlation between osmolarity with DED signs and symptoms were summarized using Pearson correlation coefficient (