Purpose: To assess macular thinning in individuals with prediabetes or type 2 diabetes without diabetic retinopathy (DM2 w/o DR) compared with individuals with normal glucose metabolism (NGM).

Methods: Using spectral domain optical coherence tomography (SD-OCT), we measured macular thickness in six subfields as defined by the Early Treatment Diabetic Retinopathy Study (ETDRS) in 1838 participants from The Maastricht Study, a population-based cohort study (mean age 59 +/- 8 years, 49% men, 1087 NGM, 279 prediabetes, 472 DM2 w/o DR). Multivariable linear regression was used to assess the association between macular thickness and glucose metabolism status.

Results: After adjustment for age, sex and spherical equivalent, individuals with prediabetes showed a significant decrease in pericentral superior macular thickness [b = 2.14 lm (95% confidence interval (CI): 4.24 to 0.03), p < 0.05] compared with individuals with NGM. In individuals with DM2 w/o DR, the fovea [b = 4.05 lm (95% CI: 6.30 to 1.79), p < 0.001] and the four pericentral quadrants (range: b = 4.64 to 5.29 lm, p < 0.001) were significantly thinner compared with individuals with NGM. There was a significant linear trend of macular thinning with severity of glucose metabolism status in five subfields (p < 0.001).

Conclusion: Macular thickness is reduced in prediabetes and a greater reduction occurs in DM2, even before DR is clinically present. About half of the thinning observed in DM2 w/o DR was already found in prediabetes. Generalized thinning of the macula could be related to thinning of the temporal side of the optic nerve head through the connecting papillo-macular bundle.