Abstract
Background Confocal corneal microscopy is an excellent new noninvasive tool for assessing diabetic peripheral neuropathy. We aimed to investigate the clinical variables associated with corneal nerve parameters and establish reference values for clinical use in healthy Chinese adults. Methods The study enlisted 257 healthy volunteers (137 females and 120 males) from two clinical academic centers in China. Two experts captured and selected images of the central corneal subbasal nerve plexus at each center using the same corneal confocal microscopy instrument according to a commonly adopted protocol. Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) were measured using fully automated software (ACCMetrics). The correlation between clinical indicators and confocal corneal microscopy measures was determined using partial correlation. Quantile regression was used to calculate reference values and estimate the effects of clinical factors on the normative values of confocal corneal microscopy measures. Results Females had significantly higher CNFD, CNBD, and CNFL than males. There was no correlation between age, glycated hemoglobin (HbA1c), height, weight, body mass index (BMI), and any corneal nerve fiber parameter in both sexes. In either sex, age, weight, height, BMI, and HbA1c did not affect the 0.05th quantile values of any corneal nerve parameter. Conclusions This study establishes sex-adjusted reference values for corneal confocal microscopy measures in Chinese adults and provides a reference for clinical practice and research with this technique.
Highlights
Diabetic peripheral neuropathy (DPN), for which there is currently no effective therapy, affects nearly 50% of people with type 2 diabetes mellitus [1]
Correlation analysis indicated that Corneal nerve fiber density (CNFD) (r = 0:17, P = 0:007), corneal nerve fiber length (CNFL) (r = 0:16, P = 0:011), and corneal nerve branch density (CNBD) (r = 0:12, P = 0:048) were significantly correlated with sex and CNFD (r = −0:13, P = 0:044) was significantly correlated with height
Sex and height were entered into the stepwise multiple linear regression model, and it was found that only sex entered the model and showed a significant correlation with CNFD
Summary
Diabetic peripheral neuropathy (DPN), for which there is currently no effective therapy, affects nearly 50% of people with type 2 diabetes mellitus [1]. The application of corneal confocal microscopy (CCM) may provide a fast, reliable, and noninvasive alternative method for detecting and diagnosing peripheral neuropathies, especially DPN. A standardized, automated image analysis program (ACCMetrics) has been widely used [16, 17] It allows for the objective and rapid calculation of strictly defined corneal nerve parameters, avoiding interand intraobserver differences in manual analysis and allowing for study comparisons [18]. We evaluated corneal nerve parameters in Chinese adults using ACCMetrics in multiple research centers to investigate the effect of clinical factors on CCM measures and establish reference values for CCM parameters in Chinese adults. This study establishes sexadjusted reference values for corneal confocal microscopy measures in Chinese adults and provides a reference for clinical practice and research with this technique
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