Correlation between choroidal and retinal thickness in diabetic patients without diabetic retinopathy

Purpose This study was design to examine the correlation between retinal and choroidal thickness in diabetic patients without diabetic retinopathy. Methods 125 type 2 diabetic patients without diabetic retinopathy underwent a complete ophthalmological examination. Retinal total thickness and retinal layer automatic segmentation were assessed by using spectral domain optic coherence tomography (Spectralis Heidelberg Engineering). Retinal measures were made at fovea and at 3 mm temporal (T3), nasal (N3), superior (S3) and inferior (I3) to the fovea. Choroidal Thickness (CT) was assessed with enhanced depth mode (EDI) software (subfoveal and at 1,000 μm temporal, nasal, superior and inferior to the fovea). Pearson correlations were analyzed between CT and RT (total and by layer) at the five locations of study: subfoveal CT with central RT; and CT at the 1,000 μm temporal, nasal, superior and inferior to fovea's center with RT at the T3, N3, S3 and I3, respectively. Results Diabetic patients were in average 66.9 ± 9.33 years old with an average disease duration of 93.50 ± 81.74 months. Except for the pigmented epithelium retinal layer, which showed a positive, but weak correlation with CT at N3, S3 and I3 (r between 0.25 and 0.32, p < 0.05), the analyze didn't showed a statistical significant correlation between CT and the thickness of the other retinal layers. Conclusions Recent studies empathize the role of a choroidal vasculopathy in diabetic retinopathy pathogenesis. The absence of correlation between CT and RT may be related to changes in the choroid occur in earlier stages of the disease. Future longitudinal studies are needed in patients at different stages of diabetic retinopathy.