Choroidal vascularity index in schizophrenia and bipolar disorder

This study examined differences in choroidal structural parameters, including the choroidal vascularity index, among patients with schizophrenia, bipolar disorder, and healthy controls.

This cross-sectional study included 40 patients with bipolar disorder type I in remission, 40 clinically stable patients with schizophrenia, and 40 age- and sex-matched healthy controls. Enhanced depth imaging optical coherence tomography was used to obtain subfoveal choroidal images. Total choroidal area (TCA) and luminal area (LA) were measured by image binarization using ImageJ software, and the choroidal vascularity index (CVI), as the ratio of LA to TCA, was calculated. Group comparisons, correlation analyses, and analyses of covariance were performed.

TCA was found higher in schizophrenia (2.52 ± 0.47 mm²) and bipolar disorder (2.45 ± 0.36 mm²) compared with healthy controls (2.07 ± 0.24 mm²) (p < 0.001). LA indicated a similar pattern (schizophrenia: 1.65 ± 0.29 mm²; bipolar disorder: 1.57 ± 0.24 mm²; healthy controls: 1.36 ± 0.14 mm²; p < 0.001). CVI was lower in bipolar disorder (0.64 ± 0.02) compared with healthy controls (0.66 ± 0.03) (p = 0.009), and no significant difference was observed between schizophrenia and controls (p > 0.05).

Increased TCA and LA were observed in both schizophrenia and bipolar disorder, whereas CVI values were lower in bipolar disorder. Findings were independent of metabolic parameters and symptom severity. Choroidal structural measurements may provide additional information about microvascular characteristics in severe mental illnesses.