Stratified choroidal vascular structure in treatment-naïve diabetic retinopathy.

Objective: To analyze the anatomical choroidal vascular layers in topical treatment-naïve diabetic retinopathy (DR) eyes.

Design: A retrospective, clinical case-control study.

Methods: A total of 328 eyes from 228 patients with treatment-naive DR and 192 eyes matched for axial length from 174 healthy controls were enrolled in the study. Choroidal structure was quantitatively analyzed using enhanced depth imaging optical coherence tomography (EDI-OCT). Each choroidal vascular layer was divided into the choriocapillaris, Sattler's layer, and Haller's layer, and then the choroidal area (CA), luminal area (LA), stromal area (SA), and central choroidal thickness (CCT) were calculated using binarization techniques. The ratio of LA to CA was defined as the L/C ratio.

Results: In the choriocapillaris, CA was significantly lower in the mild/moderate non-proliferative DR (mNPDR) group than in the control group, and SA was significantly higher in all DR groups (each P < 0.01). The L/C ratio was significantly lower in all DR groups than controls (P < 0.01). In Sattler's layer, CA, LA, and SA were significantly higher in the severe NPDR (sNPDR) and PDR groups than in the control group (P < 0.01). In Haller's layer, the L/C ratio was significantly high among the PDR groups (P < 0.05).

Conclusions: The choroidal parameters of DR patients by the binarization method were associated with the stage of DR, in which the choriocapillaris lumen decreased in all the DR stages. The expansion of CA seen in more advanced DR eyes mainly resulted from changes in the Sattler's and Haller's layers.