Alteration of layer thickness in the choroid of diabetic patients

Importance Choroidal thickness changes in diabetic retinopathy improve the understanding of the pathophysiology and managements of this disease. Background Design To examine the choroidal layer thickness in diabetes mellitus (DM) patients and normal individuals, and to compare the findings based on medical history of systemic DM treatments, and stage of diabetic retinopathy (DR). Case control study. Participants Methods Two hundred and sixty-eight eyes of 134 DM patients and age-matched 72 healthy controls of 92 eyes. Central choroidal layer thickness (total, inner and outer layers) was measured using enhanced depth imaging OCT. DM patients were divided into two groups; the DM-treated group (88 cases), and the untreated group (46 cases). These two groups were further classified into four groups; no DR (NDR), mild/moderate non-proliferative DR (mNPDR), severe NPDR and PDR. Main Outcome Measures Results Comparison of subfoveal choroid layer thickness in control and diabetic patient groups. Choroidal thickness measurements of diabetic eyes had strong correlation between masked raters in choroidal layers, proving high reproducibility. The total and outer choroid thicknesses in mNPDR in the DM-untreated group were significantly thinner than normal controls (each P < 0.05). Choroidal outer layer thickness of the severe NPDR in the DM-untreated group was significantly thicker than normal controls (P < 0.05). In the DM treatment group, there were no significant differences from the control group regarding choroidal layer thicknesses and all stages of DR. Conclusions and Relevance The choroidal thickness significantly changed in the DM-untreated group, and the main anatomical changes might result from the outer layer.