Deep retinal layer microvasculature alterations in schizophrenia

A subset of individuals with schizophrenia (SZ) are thought to have a microvascular component to their illness with studies demonstrating alterations in retinal superficial, deep, and choroidal microvasculature networks. However, the direction and location of these alterations have differed across studies. In a recent study, we reported that individuals with SZ demonstrated lower superficial layer perfusion density than a healthy control (HC) group. The current study investigated characteristics of the deep vascular layer in SZ. We included 28 individuals with a diagnosis of SZ or schizoaffective disorder, and 37 HCs. Optical coherence tomography angiography (OCTA) data was collected to measure deep retinal layer perfusion density, skeletonized vessel density, vessel diameter index, and fractal dimension. We conducted between-group comparisons to examine differences in these OCTA variables between SZ and HC groups. A trend analysis was conducted to determine if differences reflected a linear trend according to age and illness length, and Spearman correlations were conducted to determine associations between deep and superficial layer density. Individuals with SZ demonstrated significantly lower bilateral perfusion density and vessel diameter index, as well as lower left eye skeletonized vessel density and fractal dimension. There was a significant linear trend in the data indicating that individuals with chronic SZ demonstrated the lowest OCTA values, followed by individuals within two years of their first episode of psychosis who did not differ from older controls, followed by younger controls, who demonstrated the highest values in at least one eye. Lower density values in the deep retinal layer were also significantly associated with lower density values in the superficial layer. Overall, results suggest that microvascular alterations are present in multiple retinal layers in SZ and that they may be useful visual system biomarkers of neurovascular changes in the disorder.