Objective: The human eye is an embryological protrusion of the brain, and the nerves and axons of the retinal nerve fiber layer (RNFL) are similar to those in the brain. The retina, which does not have a myelin sheath, is widely accepted as a good region for understanding neurodegeneration and proposed as a window to the brain. The retina is rich in dopamine and glutamate, which are generally supposed to be dysregulated in various psychiatric disorders. Ongoing neurotropic effects of ECT/ECS have been shown in hippocampus, prefrontal cortex, amygdala and hypothalamus in preclinical and clinical studies. Here, for the first time, we aimed to investigate ECT-induced neurotropic effects on the retinal nerve in patients who were indicated for ECT.
Methods: The data of 10 (F=8 and M=2) eligible patients who have indicated ECT were obtained. All patients were under drug treatment and no change was made during ECT sessions. Participants with conditions that may affect the retinal nerve fiber layers and with a presence of additional neurological conditions were excluded from the study. After dilation of pupils, all participants underwent RNFL thickness measurement by OCT (Stratus OCT, software version 4.0.1; Carl Zeiss Meditec Inc., Dublin, CA, USA).
Results: There were five patients with treatment-resistant depression, three with bipolar depression and two patients with schizophrenia in the sample. The mean age of the participants was 50.30±11.73 years. The mean ECT session was 5.7±1.70 and mean ECT duration was 160.50±50.06sec. The central macula thickness in the right eye was significantly increased after ECT (238.00±22.82 vs. 241.50±22.38, p=0.038) while there was a slight increase after ECT in the left RNFL (92.40±14.04 vs. 96.40±10.75, p=0.081).
Conclusion: In the literature, the findings of RNFL thickness and macular volume are inconsistent in patients with schizophrenia. The main confounders for these inconsistencies were inadequate resolution of the OCT method to find subtle changes in the early phase of schizophrenia and being under drug treatment. Interestingly, no study on RNFL was found in depression and/or bipolar depression and the influences of treatment. In rats, valproic acid exerted growth effects on the retinal nerve. This is the first prospective study that dealt with the outcome of ECT on RNFL. We have shown thickening of the right macula and a slight thickening of left RNFL. However, one must keep in mind when interpreting our conclusions that these findings were preliminary and the patients were under treatment.