Abstract Background Optical coherence tomography (OCT) has been recently used to investigate neuropsychiatric disorders. Objective The aim of this study was to compare the retinal nerve fiber layer thickness (RNFLT) and the ganglion cell layer (GCL) volume in patients with type 1 bipolar disorder (BPD1, diagnosed according to DSM 5) to the values in healthy controls. Methods Eighty consecutive outpatients with a diagnosis of euthymic BPD1 and 80 healthy controls were enrolled in the study. Following assessment with the Sociodemographic Data Form, Structured Clinical Interview for DSM-IV (SCID-I), Hamilton Depression Scale and Young Mania Evaluation Scale, both groups underwent Optical coherence tomography (OCT). Results The mean RNFL thickness and mean GCL volume were significantly lower in the BPD1 group than in the controls (p < 0.05). The GCL global value had a significant and independent effect in distinguishing the BPD1 patients from the controls. A cut-off value of 101 mm3 for global GCL volume was proposed to distinguish BPD1 patients from controls with a sensitivity of 87.5%. Discussion Lower values of GCL volume and RNFLT in patients suffering from BPD1 suggest that neurodegeneration may occur during the course of BPD and that this degeneration can be characterized in particular by a thinning of the GCL volume.