Statistical analysis
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Data analysis was performed using IBM® SPSS® statistics 17.0 software (SPSS Inc. Released 2008. SPSS Statistics for Windows, Version 17.0. Chicago). The normal distribution of variables was examined using the Kolmogorov-Smirnov test, which was suitable for our sample sizes. Median, minimum and maximum values and percentages were used to present quantitative data. Changes from baseline to follow-up examinations are presented descriptively as trend directions in the outcome response. Change within group was assessed by calculating the change in variables (follow-up value minus baseline value) and reported as median difference. Student’s t-test was used to compare baseline demographic and clinical characteristics between groups and descriptive statistics were calculated for demographic data. Cohen’s d coefficient was used to calculate the effect size for change in each group (mean SD of differences). Effect sizes were divided into three categories: small ‘0.20–0.49’, medium ‘0.50–0.80’ and high ‘>0.8’. A P-value less than 0.05 was considered statistically significant.