Comparison of optical coherence tomography findings of patients diagnosed with schizophrenia using first generation antipsychotic, clozapine, and second generation antipsychotics other than clozapine with control group

In recent years, optical coherence tomography (OCT) has been used by various researchers to investigate neuronal degeneration in schizophrenia due to its features such as noninvasive, easy to apply and time-saving, and some changes in retinal structures have been detected according to healthy controls. However, the effect of antipsychotic (AP) drugs on OCT findings in schizophrenia has not yet been fully elucidated. In this study, we aimed to investigate the effects of AP treatment subgroup on OCT findings in patients diagnosed with schizophrenia. The study consisted of three subgroups of patients diagnosed with schizophrenia according to the Diagnostic and Statistical Manuel of Mental Disorders, 5th Edition (DSM-5) criteria and treated with the first generation antipsychotic group (FGAG), the second generation antipsychotic group (SGAG) and the clozapine group (CG) in the psychiatric outpatient clinic of Adiyaman University Training and Research Hospital. In this retrospective study, the patient group was also divided into two groups called treatment resistant schizophrenia (TRS) and non-treatment resistant schizophrenia (N-TRS). Sociodemographic data and psychometric scales obtained from the patient registration system were used. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and choroidal thickness for both eyes were measured using a spectral OCT device. As a healthy control group, patients who were not diagnosed with disease and who did not use drugs were included. SPSS 22.0 was used for data analysis and 0.05 or below has been accepted as significant (p value). Based on inclusion and exclusion criteria, the study included 82 (18 female, 64 male) patients, 50 healthy controls (18 female, 32 male). There was no a significant difference between the control group and the patient group and between FGAG, SGAG, and CG in terms of age for both genders (p<0.05). Education and work status of the patient group is lower than in the control group, the rate of being unmarried in terms of marital status was more frequent in the patient group (p<0.05). In the TRS group, the positive and negative syndrome scale (PANSS) and the clinical global impression scale (CGI) scores, the number of hospitalization, and attacks were higher than the N-TRS group (p<0.05). There were significant differences between the patient group and control group; between the control group and TRS, N-TRS groups; and between control group and FGAG, SGAG, and CG in terms of RNFL and its sub parameters (p<0.05). No significant difference was found between FGAG, SGAG, and CG (p>0.05) while there was a significant difference between the control group and the patients with schizophrenia group, more prominent in TRS, in terms of GCL and IPL (p<0.05). In terms of the choroidal thickness that SGAG has the highest value for both eyes; the choroidal layer thickness of control group, CG, and FGAG decreased with the same order. A non-significant difference between the SGAG and the control group (p>0.05), a significant difference between SGAG and CG, FGAG (p<0.05), a significant difference between control group and FGAG (p<0.05) were found. When our findings were evaluated and interpreted in the light of the literature, it is observed that our sociodemographic data support the loss of cognitive and social functioning due to schizophrenia. Resistance to treatment adversely affects the parameters associated with the disorder process. The fact that RNFL sub parameters were different in the patient groups compared to the control group was considered as an indicator of axonal degeneration. It was observed that schizophrenia caused thinning in GCL and IPL and there was a negative correlation between these parameters and resistance to treatment. These findings suggest that schizophrenia is a neurodegenerative disorder and this neuronal degeneration correlated with the severity of the disorder. The absence of a significant difference between FGAG, CG, and SGAG in terms of GCL and IPL suggests that the course and severity of the disorder play an important role in the pathophysiology of neuronal degeneration, rather than the AP drugs used. The presence of the choroidal layer thickness of SGAG was thicker than the control group, and the choroidal layer thickness of SGAG was less than FGAG and CG were associated with the deterioration of the metabolic parameters of the SGA use. Thinner choroidal layer thickness in the CG compared to the SGAG and control group was thought to be related to the patients with schizophrenia using clozapine had a resistance to the treatment and antiinflammatory properties of clozapine. Thinner choroidal layer thickness in the FGAG compared to the other drug sub groups and control group was associated with the use of FGAG in accordance with the literature in daily practice when there was not sufficient response to the SGAG, evaluation of an intermediate stage treatment prior to the switch to clozapine, and re-use of FGAs in TRS that did not respond to clozapine treatment.