Eye-tracking-derived foveal biomarkers and functional alterations in dry AMD: findings from a controlled clinical study.

PURPOSE: Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly, and early detection is essential for timely intervention and slowing disease progression. This study validated novel foveal function tests using the Bulbicam (BCAM) device for differentiating early and intermediate dry AMD from healthy controls (HCs) and to identify functional variables that may serve as candidate biomarkers. METHODS: In a controlled clinical study, 17 patients with early and intermediate dry AMD and 17 age-matched HCs were assessed using the proprietary Bulbitech “ACOLAPT” (Acuity, Contrast, Light Adaptation) test. Each eye was classified as either the “Worst eye” or “Best eye” for AMD patients based on predefined clinical criteria. Foveal function metrics were derived from the five main variables: Pursuit acuity (PuAc), Pursuit contrast sensitivity (PuCS), Strobe Pursuit Contrast Sensitivity(StCS), (PuCS − StCS) / PuCS (ΔCS), and Variable Strobe Pursuit Object Detection(VaSt). Test validity, reliability, repeatability, and stability were assessed. Validation of ACOLAPT included Analysis of Variance (ANOVA) and Receiver Operating Characteristic (ROC) analyses to assess discriminative capacity, intraclass correlation coefficients (ICC) and Bland-Altman plots with Agreement Index (AI) to evaluate reliability and Stability Index (SI) for estimation of stability. RESULTS: All five BCAM tests showed significant differences between AMD patients and HCs in the worst eye (p ≤ 0.05). PuAc and PuCS showed good reliability (ICC ≥ 0.77), good repeatability (AI ≥ 0.75), and excellent stability (SI ≥ 0.59). The novel StCS test demonstrated excellent reliability (ICC = 0.96), excellent repeatability (AI = 0.88), and excellent stability (SI = 0.58). Despite good ICC values, VaSt and ΔCS had lower repeatability (AI ≤ 0.25), highlighting the importance of AI and SI metrics. CONCLUSION: PuAc, PuCS, and StCS fulfilled the predefined criteria for reliability, repeatability, and stability, supporting their use as candidate biomarkers at both population and individual patient levels. VaSt also met the predefined biomarker criteria through preserved cross-session stability despite lower single-trial agreement. ACOLAPT’s ability to assess multiple aspects of foveal function, along with enhanced stability and repeatability metrics, suggests that it could be valuable in clinical settings for early AMD detection and monitoring.