Statistical analyses
Statistical analyses were accomplished using a commercially available software program (PASW Statistics 18). Specificity and relevance of quantitative differentiations were established by ANOVA p-values and results were expressed as mean values ± SD (standard deviation). In relation to serotransferrin tear levels, since none of the groups showed a normal distribution (Shapiro-Wilk’s test p<0.05), sample values were expressed by median ± interquartile range (IRQ). Comparison among groups was performed by U Mann-Whitney test with normal approximation and 0.5 continuity correction. For statistical significance, the threshold p value was p< 0.05.