An investigation of retinal layer thicknesses in unaffected first-degree relatives of schizophrenia patients.

Introduction: A large number of studies using different neuroimaging methods showed various structural changes both in patients and their unaffected first-degree relatives (FDRs) over the past years. Optical coherence tomography (OCT) is a relatively new, non-invasive imaging method used to obtain high-resolution cross-sectional images of the retina. A growing body of evidence reports thinning of retinal layers in patients with schizophrenia which is considered as a proxy for CNS alterations. We hypothesized that retinal layer changes would be observed in FDRs, in parallel with those seen in patients, as a potential endophenotype candidate.

Methods: Thirty-eight schizophrenia patients, 38 FDRs of schizophrenia and 38 age and gender-matched healthy subjects with no family history (HCs) were recruited to this study. OCT measurements were performed and peripapillary retinal nerve fibre layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and macular thicknesses were measured.

Results: The groups did not differ on RNFL, macular or GCL thickness. However, IPL thickness was significantly lower in both patients and FDRs than HCs (p = .025 and p = .041, respectively). The difference between groups remained significant after controlling for confounders such as age, gender, smoking status, comorbid medical diseases and BMI (p = .016 patients vs HCs and p = .014 FDRs vs HCs).

Conclusion: Our findings suggest that IPL thinning may hold promise as a useful endophenotype for genetic and early detection studies. The evaluation of this area could provide an important avenue for elucidating some of the neurodevelopmental aberrations in the disorder.