Retinal Microvascular Biomarkers May Suggest Euthymic Bipolar Disorder

Retinal neuronal degeneration and vascular dysfunction are common among individuals with euthymic bipolar disorder (BD), according to research published in the Journal of Affective Disorders.

Researchers enrolled 48 participants with BP (mean age [SD], 37.5 [10.38] years; 70.80% women) who had been in remission for at least 6 months and 45 age-matched control individuals (mean age [SD], 37.20 [10.59]; 35.60% women in the study. Patients underwent retinal vessel density, retinal nerve fiber layer (RNFL), ganglion cell inner plexiform layer (GCIPL), foveal avascular zone (FAZ) and radial peripapillary capillary plexus (RPCP) measurements. The primary objective was to identify associations between BD and retinal vascular changes.

According to the report, patients in the BD group had thinner mean average RNFL thickness (100.933 vs 109.20 µm; P =.000), superior RNFL thickness (125.711 vs 135.458 µm; P =.012), nasal RNFL thickness (70.155 vs 85.333 µm; P =.000), and inferior RNFL thickness (129.488 vs 139.854 µm; P =.042) compared with control group participants. The BD group participants also had lower superficial (38.888% vs 42%; P =.001) and deep (32.911% vs 35.208%; P =.011) vessel density values compared with control individuals.  

A subgroup analysis of patients with BD determined differences in terms of the relationship between the variables and medication use. Mean RNFL thickness was significantly thinner among individuals taking a combination of lithium and valproate compared with patients not using mood stabilizers (P =.013) and thinner among individuals using lithium compared with those using a lithium and valproate combination (P =.031). Superficial vessel density was higher among individuals using lithium (P =.001) or valproate alone (P =.019) compared with those using a combination of the treatments.

“BD is a disorder that is associated not only with retinal neuronal degeneration such as RNFL but also with vascular dysfunction with parameters such as RPCP and [vessel density], as in our study,” according to the researchers. “Within this context, [optical coherence tomography angiography] can reflect both diagnostic support and association with some clinical features in patients with BD.”

Study limitations include confounding due to drugs other than mood stabilizers and failure to differentiate between patients of varying BD severity.