2.4. Statistical analysis

The Statistical Package for Social Sciences (SPSS Version 19.0; Cary, NC, USA) was used to perform the statistical analysis. The results are expressed as mean±standard deviation (SD). The Kolmogorov-Smirnov test was used to test the normality of the data. Paired t-test was used to compare LTMH, CTFT, and CCET between operated and fellow eyes; independent t-test was used to compare LTMH, CTFT, CCET and other normally distributed variables between males and females and between keratoconus and other primary diseases, while the Mann-Whitney U-test was used for non-normally distributed variables. Correlations of LTMH, CTFT, and CCET between operated and fellow eyes were tested using the Pearson’s correlation coefficient; correlations between LTMH, CTFT, CCET and other demographic or clinical data were analyzed using Pearson’s correlation coefficient (for normally distributed variables) or Spearman’s correlation coefficient (for non-normally distributed variables). The significance level was set to P<0.05.