Optical coherence tomography neurodegenerative findings in patients with bipolar disorder

Introduction Neuroimaging studies of patients with bipolar disorder (BD) have recently revealed neurodegenerative changes in the central nervous system. Optical coherence tomography (OCT) imaging of the retina, as an extension of brain, may be a biomarker in understanding the neurobiology of the disease. To assess OCT as a tool to detect neurodegeneration in BD we compared the retinal changes between patients with BD and healthy individuals. Methods We performed complete ophthalmological examinations and took OCT images for 70 eyes of 70 patients with BD, and for age and sex-matched individual controls. We compared retinal nerve fiber layers (RNFLs) and total retinal (TR) thickness in the peripapillary areas; and ganglion cell complexes (GCCs) and TR thickness in the maculas between the groups. Results The mean age of the patients was 40.41 +/- 13.22 years and that of the controls 40.20 +/- 13.03 years. The men/women ratios were 37/33 in both groups. BD was significantly associated with a decrease in the average peripapillary RNFL, with the average peripapillary TR, and with the average GCC thickness (P = .033, P = .008, and P = .009, respectively). The peripapillary RNFL and TR thinnings were prominent in the superior (P = .039, P = .033, respectively) and inferior quadrants (P = .031, P = .018, respectively). The BD effects on GCC thinning was prominent in the superior half (P = .001) and in the nasal sectors (except in the inner superonasal sector; all P < .05). BD was associated with a decrease in macular TR thickness only at the inner superior sector (P = .014). Disease duration was inversely correlated with the peripapillary RNFL, TR, and macular GCC thicknesses (P < .05). Discussion Our findings support the neurodegeneration hypothesis in the etiopathogenesis of BD. OCT, a non-invasive neuro-imaging method, may be useful for BD diagnosis and follow-ups.