Bilberry (Vaccinium myrtillus) is a small European shrub berry with a long history of use in traditional medicine, particularly for supporting vision. The primary active compounds in the berry are anthocyanins, which are potent antioxidant pigments responsible for the fruit’s deep blue color. Elevated eye pressure, known medically as Intraocular Pressure (IOP), is a significant concern because sustained high pressure is the primary modifiable risk factor for optic nerve damage, which can lead to glaucoma. The central question is whether this botanical can directly influence and lower this pressure.
The Science Behind Bilberry and Ocular Health
The general benefits of bilberry for the eye are rooted in the biological actions of its anthocyanins. These compounds exhibit powerful antioxidant and anti-inflammatory properties, which help to protect the delicate structures of the eye from oxidative stress. Oxidative damage is a key factor in the aging and degeneration of retinal cells, making this protective effect relevant for long-term visual health.
Anthocyanins are also known for their vascular effects, which include improving microcirculation and strengthening the integrity of capillaries. The eye, particularly the retina, relies on a dense network of microvessels for oxygen and nutrient delivery, and bilberry may enhance blood flow to these tissues. Furthermore, laboratory studies suggest that anthocyanins may have a relaxing effect on the ciliary muscle, which influences the drainage of internal fluid.
Direct Evidence Regarding Intraocular Pressure Reduction
While bilberry has established benefits for ocular circulation and cell protection, direct evidence of its ability to significantly lower Intraocular Pressure (IOP) on its own is limited and often inconclusive. Most promising clinical data involves bilberry used in combination with another botanical extract, French maritime pine bark, rather than bilberry as a standalone treatment. This specific combination has been tested in small-scale human trials involving patients with ocular hypertension or primary open-angle glaucoma (POAG).
In one study, patients with asymptomatic ocular hypertension saw their average IOP drop after three months of taking the combination supplement. Another trial on POAG patients, who were already using prescription eye drops, showed a further reduction in mean IOP with the addition of the combined extract. The IOP-lowering effect is thought to be related to a potential pressure-reducing mechanism and the extracts’ ability to improve blood flow to the optic nerve.
The current scientific consensus is that these results are encouraging, but the trials are generally small, and the effects are linked to the synergistic action of the two ingredients. Bilberry extract alone has not been shown to reliably match the efficacy of prescription glaucoma medications. Therefore, while bilberry may offer supportive benefits for eye health and circulation, it cannot be considered a primary treatment for elevated IOP or glaucoma.
Practical Considerations for Bilberry Supplementation
For those considering bilberry supplementation, extracts are typically standardized to contain a specific amount of anthocyanins to ensure consistent potency. Common dosages in studies range from 160 to 480 mg of standardized bilberry extract per day.
Bilberry is generally well-tolerated, but potential interactions with certain medications exist. Due to its possible mild antiplatelet effects, bilberry may increase the risk of bleeding when taken alongside blood-thinning medications, such as warfarin or aspirin. People taking antidiabetic drugs should also use caution, as bilberry may have a modest blood-sugar-lowering effect.
It is necessary for anyone with diagnosed or suspected high eye pressure to consult with an ophthalmologist before starting any supplement regimen. Bilberry supplementation must not be used as a substitute for prescribed treatments for conditions like glaucoma. The risk of irreversible vision loss from untreated high IOP outweighs any unproven benefit from a dietary supplement.