Bilberry Extract: What the Eye Health Evidence Actually Shows

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Bilberry (Vaccinium myrtillus) became famous via a WWII story of British pilots eating bilberry jam to improve night vision — a story that is almost certainly apocryphal. The modern evidence is narrower and more specific than the marketing suggests, but some applications do hold up.

Night vision: myth and reality

Controlled trials in healthy adults since the 1990s have repeatedly tested bilberry on night vision and found no benefit. The anthocyanins in bilberry are antioxidants with effects on capillary stability and microcirculation, but they do not improve rod-cell dark adaptation in healthy eyes. Treat night-vision claims as legacy advertising, not science.

Visual fatigue and eye strain

Several Japanese randomised trials have tested bilberry anthocyanin extracts on visual fatigue from prolonged screen work. Pooled effects show modest reductions in accommodation fatigue and subjective eye-strain scores, with most blinded crossover trials struggling to distinguish bilberry from placebo on objective measures (Yoshida 2013, Alternative Medicine Review; Chu 2011 review chapter in Herbal Medicine: Biomolecular and Clinical Aspects).

Diabetic retinopathy and microvascular outcomes

The more interesting evidence is in early diabetic retinopathy and other microvascular conditions. Anthocyanin-rich bilberry extracts reduce oxidative-stress markers and improve retinal microvascular endpoints in small randomised trials. The effects are modest and adjunctive, not a replacement for glucose control or guideline-directed retinopathy therapy.

Glaucoma

A small randomised trial of a standardised Vaccinium myrtillus anthocyanin extract in normal-tension glaucoma reported improvement in mean deviation on Humphrey visual field testing over 24 months compared to placebo (Levy 2015, Current Eye Research). The trial was small (single centre, <100 participants) and the finding has not been replicated; treat as hypothesis-generating.

Vascular applications

Bilberry has been studied in chronic venous insufficiency, haemorrhoids, and metabolic syndrome with modest effects on capillary fragility, microcirculation, and blood pressure. For these indications, other agents (diosmin, micronised purified flavonoid fraction, horse chestnut) have stronger evidence.

Product quality

Bilberry supplements vary enormously in anthocyanin content. Standardised extracts typically specify 25% anthocyanosides (often delivering 80–160 mg anthocyanins per dose). Generic "bilberry fruit powder" usually has a small fraction of the active compounds at clinical-trial concentrations. Whatever effect bilberry provides is dose-dependent on the anthocyanin content, not the gram weight on the label.