Flicker Electroretinogram in Schizophrenia and Depression

Abstract Background: Schizophrenia is a heterogeneous psychiatric disorder with few reliable diagnostic biomarkers and diagnosis based essentially on clinical criteria. Electroretinogram (ERG), a noninvasive retinal electrophysiological test, has shown promise as an objective tool in psychiatric research. This study evaluated Flicker ERG responses using a portable nonmydriatic device in cases of schizophrenia and depressive episode and compared with healthy controls. The particular ERG protocol and device were selected as they offer easy and fast acquisition of ERG in a busy outpatient department and real-world scenario. Methods: This observational study was conducted at a tertiary care hospital. Forty cases each diagnosed with schizophrenia or depressive episode and 80 healthy controls were enrolled. Flicker ERG recordings were obtained using Reteval-DR™ at two stimulus strengths (16 Td·s, 32 Td·s). Amplitudes and implicit times of the Flicker response were recorded as primary objective parameters. Pupillary response and DR score, a derived parameter from the machine, were recorded as secondary objective parameters. Cases of schizophrenia were re-assessed after 2 months of treatment. Statistical analysis included analysis of variance, post hoc comparisons, and receiver operating characteristic (ROC) analysis. Results: Groups were comparable for demographic features. Cases of schizophrenia showed significantly reduced Flicker ERG amplitude, prolonged implicit time, and altered pupillary response compared to controls ( P < 0.05). Depressed patients also showed abnormalities, though less marked. No significant change was observed in cases of schizophrenia after 2 months of treatment. ROC analysis identified amplitude (of 16 Td. s stimulus, with cutoff 17.4 µV) as most specific (specificity 86%), while DR score and implicit time 2 (of 32 Td. s stimulus, with cutoff 23.8 ms) provided the highest diagnostic accuracy and sensitivity. Conclusion: Portable nonmydriatic Flicker ERG provides a rapid, objective method to detect electrophysiological abnormalities in schizophrenia and depression. Findings support its potential as a screening tool. Validation by larger and longer-term studies is warranted.