Plasma Metabolites Associated with OCT Features of Age-Related Macular Degeneration

Abstract

Purpose: The most widely used classifications of age-related macular degeneration (AMD) and its severity stages still rely on color fundus photographs (CFPs). However, AMD has a wide phenotypic variability that remains poorly understood and is better characterized by OCT. We and others have shown that patients with AMD have a distinct plasma metabolomic profile compared with controls. However, all studies to date have been performed solely based on CFP classifications. This study aimed to assess if plasma metabolomic profiles are associated with OCT features commonly seen in AMD.

Design: Prospectively designed, cross-sectional study.

Participants: Subjects with a diagnosis of AMD and a control group (> 50 years old) from Boston, United States, and Coimbra, Portugal.

Methods: All participants were imaged with CFP, used for AMD staging (Age-Related Eye Disease Study 2 classification scheme), and with spectral domain OCT (Spectralis, Heidelberg). OCT images were graded by 2 independent graders for the presence of characteristic AMD features, according to a predefined protocol. Fasting blood samples were collected for metabolomic profiling (using nontargeted high-resolution mass spectrometry by Metabolon Inc). Analyses were conducted using logistic regression models including the worst eye of each patient (AREDS2 classification) and adjusting for confounding factors. Each cohort (United States and Portugal) was analyzed separately and then results were combined by meta-analyses. False discovery rate (FDR) was used to account for multiple comparisons.

Main outcome measures: Plasma metabolite levels associated with OCT features.

Results: We included data on 468 patients, 374 with AMD and 94 controls, and on 725 named endogenous metabolites. Meta-analysis identified significant associations (FDR < 0.05) between plasma metabolites and 3 OCT features: hyperreflective foci (6), atrophy (6), and ellipsoid zone disruption (3). Most associations were seen with amino acids, and all but 1 metabolite presented specific associations with the OCT features assessed.

Conclusions: To our knowledge, we show for the first time that plasma metabolites have associations with specific OCT features seen in AMD. Our results support that the wide spectrum of presentations of AMD likely include different pathophysiologic mechanisms by identifying specific pathways associated with each OCT feature.

Financial disclosures: Proprietary or commercial disclosure may be found after the references.

Keywords: Age-related macular degeneration/AMD; Atrophy; Hyperreflective foci; Metabolomics; OCT.

Figure 2

Representative OCT b-scan demonstrating hyperreflective foci (orange arrows) overlying a large drusenoid pigment epithelial detachment.

Figure 3

Receiving operating characteristic curves for OCT features with significant associations with metabolites. In these figures, model A includes age, sex, body mass index, and smoking status. Model B includes metabolites identified as significantly associated with each OCT feature in addition to the variables of the baseline model (i.e., for hyperreflective foci, metabolites listed in Table 3; for atrophy, metabolites listed in Table 4; and for ellipsoid zone disruption, metabolites listed in Table 5).

Figure 4

OCT b-scan demonstrating presence of atrophy (yellow arrow) – in this case incomplete retinal pigment epithelium and outer retinal atrophy (iRORA).

Figure 5

OCT b-scan demonstrating presence of ellipsoid disruption (yellow brackets) in an area overlying classic drusen.