Corneal Nerve Fiber Assessment in Diabetic Neuropathy

The primary outcome measure was corneal nerve fiber pathology as assessed with CCM. A difference in nerve fiber length of 2.7 mm/mm² has been demonstrated to be a clinically significant difference representing the difference between mean nerve fiber length in controls and individuals with mild diabetic neuropathy [34 (link)]. The standard deviation for nerve fiber length (mm/mm²) in controls has been reported to be 0.88 [35 (link)]. Using these parameters, a power of 0.80 and a two-tailed alpha of 0.05, a minimum sample size of 16 was calculated per group. Given the lack of precision associated with this calculation we increased the sample size to 20 per group to improve the power of the study.
All statistical analyses were performed using IBM SPSS Statistics software Version 26 and P<0.05 was considered statistically significant. Normally distributed data were expressed as mean ± standard deviation and the means were compared using an independent sample t-test. To investigate the association between clinical parameters and corneal nerve fibres parameters, Pearson correlation was used. Graph prism version 8 was used to build dot plots.