From the Manufacturer:
Bilberry Extract is the dry extract of the European Blueberry (Vaccinium myrtillus: Myrtilli fructus). Bilberry, used to improve vascular health, and shows the most promise for use in supporting the health of the eye.
Interestingly, this is an herbal medicine that is thousands of years into use as a folk remedy for loose stool (especially recommended for children), but it's most promising current application is for use in supporting the health of the eye. Its high levels of tannic acid, cinnamic acids, flavonols, anthocyanidins, and isoflavones make it highly beneficial to the eye.
Positive results have been noted in studies examining the effect of bilberry in pigmentary retinitis, diabetic and hypertensive retinopathy, retinal inflammation, macular degeneration, retinitis pigmentosa, glaucoma, cataract and night vision in normal subjects. The anthocyanidins in bilberry, which have the ability to protect and regenerate retinal purple (rhodopsin) are the primary agents responsible for its ability to help the eyes. At least one study we know of suggests additional benefits to the eye by adding vitamin E.