PURPOSE. The purpose of this study was to assess thinning of the peripapillary retinal nerve fiber layer (RNFL) in prediabetes or type 2 diabetes without diabetic retinopathy (DM2 w/o DRP) compared with that in individuals with normal glucose metabolism (NGM).

METHODS. We measured sectoral and mean RNFL thickness in a 3.45-mm-diameter circular scan centered on the optic nerve head, using spectral domain optical coherence tomography in 1172 participants from The Maastricht Study (a population-based cohort of individuals 59 6 8 years of age, 47% men, 699 NGM, 186 with prediabetes, and 287 with DM2 w/o DRP). Multivariate linear regression was used to assess the association between RNFL thickness and glucose metabolism status, adjusted for age and sex.

RESULTS. In individuals with prediabetes, the temporal RNFL was thinner than that in individuals with NGM after adjustment (beta = -2.28 mu m [95% confidence interval [CI], -4.44 to -0.13], P = 0.04), whereas in individuals with DM2 w/o DRP, the temporal inferior (beta = -3.66 mu m [95% CI, -6.46 to -0.85], P = 0.01), the temporal superior (beta = -2.99 mu m [95% CI, -5.95 to -0.02], P = 0.05), the temporal (beta = -2.73 mu m [95% CI, -4.62 to -0.84], P < 0.01), and the mean RNFL (beta = -1.88 mu m [95% CI, -3.51 to -0.26], P = 0.02) were thinner than those in individuals with NGM.

CONCLUSIONS. Temporal RNFL thinning is already present in individuals with prediabetes. More widespread RNFL thinning occurs in individuals with DM2 w/o DRP, that is before vascular changes are detected. This suggests preferential retinal nerve fiber layer loss in areas related to the papillomacular bundle.