Purpose: To investigate the relationship between glucose tolerance levels and the circumpapillary retinal nerve fiber layer thickness (cpRNFLT) in a general Japanese population. Design: Population-based, cross-sectional study. Methods: In 2012 and 2013, a total of 2809 Japanese community dwellers aged 40–79 years in the Hisayama Study underwent eye examinations including cpRNFLT measurement with spectral domain optical coherence tomography. Of these, 1324 subjects (578 men and 746 women) were enrolled. Glucose tolerance levels were determined by a 75-g oral glucose tolerance test. We conducted an analysis of covariance to estimate the mean values of cpRNFLT according to the subjects' glucose intolerance status. Results: The subjects with prediabetes or with diabetes mellitus had significantly lower age- and sex-adjusted mean cpRNFLT values than those with normal glucose tolerance (P =.04 and P =.0004, respectively). The age- and sex-adjusted mean values of cpRNFLT decreased significantly with elevating fasting plasma glucose and 2-hour postload glucose levels (all P for trend <.05). These associations were substantially unchanged after adjustment for potential confounding factors. The coexistence of poorer glucose tolerance and higher intraocular pressure levels was additively associated with thinner cpRNFLT. Conclusions: Our analyses revealed that poorer glucose tolerance was significantly associated with the reduction of cpRNFLT in a Japanese general population, suggesting that the loss of neural tissue in the eye begins at the prediabetic stage, and that hyperglycemia may play a role in the reduction of cpRNFLT.
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