Standardized Berry Extract Improves Selected Visual Function Outcomes in Presbyopia: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial with Exploratory Biomarker Analysis

Background/Objectives: Presbyopia is an age-related decline in near vision associated with lens stiffening and neuroretinal changes, while evidence for the effects of berry-derived phytochemicals remains limited. We investigated whether AKB, a double-standardised berry extract (anthocyanins ≥ 25%, iridoids ≥ 4.5%) from Aronia melanocarpa, Lonicera caerulea, and Vaccinium myrtillus, influences visual performance and circulating biomarkers potentially relevant to ocular homeostasis. Methods: In a randomised, double-blind, placebo-controlled, two-period crossover trial, 23 adults aged >50 years received AKB (400 mg twice daily) or placebo for 6 weeks, separated by a 5-week washout. Results: Compared with placebo, AKB was associated with improvements in selected visual-function outcomes, including near contrast sensitivity and visual-field parameters, together with directionally favourable changes in VEP and OCT readouts. AKB supplementation was also associated with lower circulating αA-/αB-crystallin and ALDH1A1 levels and higher circulating TRPV4 levels, whereas systemic antioxidant enzymes and advanced glycation end-products remained unchanged. Given the small sample size and the indirect nature of the biomarker assessment, these findings should be considered preliminary. Conclusions: Overall, short-term AKB supplementation was associated with modest, exploratory changes in selected functional and systemic biomarker outcomes, but larger and longer-term studies are needed to confirm clinical relevance and clarify underlying mechanisms.