Retinal layer abnormalities as biomarkers of schizophrenia

Objective Schizophrenia is associated with several brain deficits, as well as visual processing deficits, but clinically-useful biomarkers are elusive. We hypothesised that retinal layer changes, non-invasively visualized using spectral-domain optical coherence tomography (SD-OCT), may represent a possible “window” to these abnormalities. Methods A Leica EnvisuTM SD-OCT device was used to obtain high-resolution central foveal B-scans in both eyes of 35 patients with schizophrenia and 50 demographically-matched controls. Manual retinal layer segmentation was performed to acquire individual and combined layer thickness measurements in three macular regions. Contrast sensitivity was measured at three spatial frequencies in a sub-group of each cohort. Differences were compared using adjusted linear models and significantly different layer measures in patients underwent Spearman Rank correlations with contrast sensitivity, quantified symptoms severity, disease duration and antipsychotic medication dose. Results Total retinal and photoreceptor complex thickness was reduced in all regions in patients (P<0.0001). Segmentation revealed consistent thinning of the outer nuclear layer (P<0.001) and inner segment layer (P<0.05), as well as a pattern of parafoveal ganglion cell changes. Low spatial frequency contrast sensitivity was reduced in patients (P=0.002) and correlated with temporal parafoveal ganglion cell complex thinning (R=0.48, P=0.01). Negative symptom severity was inversely correlated with foveal photoreceptor complex thickness (R=-0.54, P=0.001) and outer nuclear layer thickness (R=-0.47, P=0.005). Samani et al. 4 Conclusions Our novel findings demonstrate considerable retinal layer abnormalities in schizophrenia that are related to clinical features and visual function. With time, SD-OCT could provide easily-measurable biomarkers to facilitate clinical assessment and further our understanding of the disease.