To investigate the association of the Fourier domain optical coherence tomography (FD-OCT, Optovue) parameters with the level of HbA1c and duration of the diabetes mellitus (DM) in patients at the early stage of diabetic retinopathy (DR).Methods
Thirty eyes of 30 patients with minimal DR (non-DR or mild NPDR) that were examined at the Chiba University Hospital from December 2011 to March 2012 were studied. The participants had no other ocular diseases and no history of surgeries. Three parameters embedded in the Optovue, the macular mapping 5 (MM5), RNFL, and ganglion cell complex (GCC), were performed, and the coefficients of correlation between these parameters and the HbA1c and the DM duration were analyzed with the Spearman rank correlation. A P<0.05 was considered significant.Results
All of the GCC parameters and RNFL parameters were not significantly correlated with both the HbA1c and the DM duration. The thickness of the outer-inferior area (mean=275.9±18.1μm) was significantly correlated with the HbA1c (P=0.046, Rs=0.371). The outer-superior area (mean=276.0±17.7μm) and the outer-temporal area (means=277.9±14.6μm) were significant correlation with the DM duration (P=0.015, Rs=0.468; P=0.022, Rs=0.439, respectively).Conclusion
The significant positive-correlation between the retinal thickness of the outer area of the MM5 sector and HbA1c and DM duration may be due to a subclinical increase of vascular permeability. It might also be due to Müller cell swelling because Müller cell density is known to be higher in the outer area than the center area.