Anthocyanins in visual performance and ocular diseases

Traditional pharmacopeia dating back centuries ago has been promoting the use of medicinal plant and animal products for the treatment of a plethora of health conditions, including eye-related diseases. For instance, bear bile has been used in Asia for more than 3000 years to treat visual disorders, and it is only recently that taurour-sodeoxycholic acid was found to be a bile constituent that promoted cell survival in models of retinal degeneration (Boatright et al. 2006). As early as the twelfth century, the German herbalist and composer Hildegarde von Bingen proposed to use bilberries as healing plants (reported in Morazzoni and Bombardelli 1996). In more recent history, the interest on bilberries for vision improvement related to their use by World War II Royal Air Force pilots who were said to ingest bilberries before their flight mission to improve their night vision (reported in Ulbricht et al. 2009). During the early 1960s, numerous studies were published in European literature supporting the claim of the beneficial effects of anthocyanins (ACNs) on the various aspects of vision such as visual acuity and dark adaptation. These claims were challenged by more rigorous, randomized, and placebo-controlled clinical studies performed more recently in normal individuals (reviewed extensively in Canter and Ernst 2004; Kalt et al. 2010). Furthermore, over the past 20 years, research involving patients with various ocular disorders has suggested that ACNs may play a significant role in the evolution of several visual dysfunctions. Other studies involving animal models of human disease have provided the supporting evidence that ACNs not only have antioxidative properties but may also have more direct involvement in the metabolic pathways, possibly acting as allosteric modulators (Yanamala et al. 2012).