Optical coherence tomography findings in bipolar disorder - A hospital-based case-control study.

Background: Studies on bipolar disorder indicate the existence of structural brain abnormalities. There is a paucity of Indian studies in this area.

Aim: To evaluate the retinal nerve fiber layer (RNFL), macular, and subfoveal choroidal thickness (SFCT) in patients with bipolar disorder type-1 (BD-1) and healthy controls.

Materials and methods: This was a cross-sectional hospital-based study in which 49 patients of BD-1 were in different phases of illness, and an equal number of normal healthy controls were taken. All the cases and controls were subjected to RNFL, ganglion cell layer (GCL), and estimation of macular thickness using spectral-domain optical coherence tomography (SD-OCT) and choroid layer thicknesses manually using the depth imaging mode of SD-OCT.

Results: The mean age of patients and the control group was 39.55 ± 5.71 and 37.91 ± 6.17 years, respectively. The mean duration of illness in different phases was 14.55 ± 10.71 years. The total number of attacks in the mania group was 4.40 ± 3.30; in the depression group, it was 3.98. ±2.82; and in the remission group, it was 4.0. ±2.20. This study found that patients with BD-1 had significantly reduced RNFL thickness, SFCT, and GCL layers compared to the healthy control group (P < 0.05). The reduction in RNFL thickness was significantly associated with the longer duration of illness.

Conclusion: The BD-1 patients evaluated in our study present structural alterations in the retina. The search for biomarkers of the disease through different ophthalmological examinations such as OCT enhances the usefulness of ophthalmological examination as a way to access the brain.