Oculomics in Bipolar Affective Disorder: Insights from Retinal Imaging

Abstract

Purpose : Neuroimaging and optical coherence tomography (OCT) studies in bipolar affective disorder (BPAD) indicate neurodegenerative changes in cortical matter and reduced thickness in the retinal nerve fibre layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL). In this study, we explored associations between BPAD and inner retinal thickness using OCT and color fundus photography (CFP) in a real-world cohort to gain insights into the neurobiology of BPAD.

Methods : The dataset originated from the retrospective AlzEye cohort, comprising 154,830 patients aged 40 years and older at Moorfields Eye Hospital, from January 2008 to April 2018. OCT and CFP were conducted as part of the clinical routine. Ophthalmic data were linked with the Hospital Episode Statistics database for systemic disease data. Macular RNFL, GC-IPL, and Inner Nuclear Layer (INL) thicknesses (μm) were extracted from OCT imaging using a retinal boundary software. Cup-to-Disc Ratio (CDR) was computed from CFP using AutoMorph, a deep learning-based tool. Linear mixed-effects models were employed to investigate the association between BPAD and retinal biomarkers, with exclusions for dementia and adjustments for demographic and systemic confounders.

Results :
209 individuals with BPAD and 96,793 controls (163,686 eyes) met our quality filters and exclusion criteria. BPAD individuals averaged 63 years old (SD±12), 65 years old (SD±14) for controls, with respectively 63% and 52% women. Individuals with BPAD were more likely to have HTN (82%vs48%) and DM (65%vs29%); p=0.001. After adjusting for age, sex, deprivation and ethnicity, the BPAD group had a thinner macular GC-IPL (-1.80μm; 95%CI:-3.50,-0.04; p=0.04), particularly in the subgroup below 55 years old (-3.94μm; 95%CI:-7.17,-0.91; p=0.01). Significance waned when considering HTN and DM (-0.81; 95%CI: -2.41,1.04; p=0.35) and in the older subgroup (-1.64, 95%CI: -3.50;0.25, p=0.08). RNFL was not significantly different. On CFP, younger subgroup CDR was higher (0.02; 95%CI:0.00,0.04; p=0.04).

Conclusions : We report a significant reduction in macular GC-IPL thickness in BPAD patients, especially those below 55 years old, accompanied by a larger cup-to-disc ratio (CDR). Although the adjustment of DM and HTN attenuated the strength of the association, these findings suggest an increased prevalence of cardiovascular risk factors that contribute to neurodegeneration in individuals with BPAD, in an ophthalmic cohort.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.