Dietary flavonoids have antioxidant, anti-inflammatory, and vascular health benefits, which align with the proposed pathophysiology of age-related eye conditions and hearing problems (hearing loss and tinnitus). The flavonoid subclass, flavonols, are protective against eye conditions, including age-related macular degeneration, cataract, and glaucoma. Dietary flavonol intake appears to be protective against some chronic eye conditions.
Six studies reported favourable associations between dietary flavonoid intake with chronic eye conditions . In particular, higher intakes of dietary flavonols were associated with a reduced risk of primary open-angle glaucoma  and reduced odds of prevalent AMD , while lower intakes of dietary flavonols were associated with poorer visual acuity related to AMD  and increased risk of age-related cataract . For glaucoma, the role of flavonols in risk reduction may be linked to antioxidant activity. This is because the pathogenesis of glaucoma and its common symptom (i.e., higher intraocular pressure) have been associated with oxidative damage to the trabecular meshwork and surrounding endothelial cells . In an experimental investigation by Miyamoto et al. , the flavonol quercetin was shown to induce the expression of antioxidant enzymes (peroxiredoxins) to reduce oxidative damage and thereby regulate intraocular pressure levels to normal levels . For AMD, flavonols have been linked to a number of pathways. One example includes the regulation of the nitric oxide status by enhancing its production and increasing the amount of circulating nitrite in order to improve endothelial function . A second example of the potential role of flavonols in AMD includes scavenging reactive oxygen species that may be causing oxidative damage to the retinal pigment epithelium cells . The integrity of the retinal pigment epithelium is important to the health of the macula and, thus, in the prevention of AMD development and/or progression . The third example includes the inhibition of retinal and choroidal angiogenesis . Experimental studies conducted in vitro have shown that quercetin inhibits angiogenesis by impacting the development and spread of new blood vessels within the choroid and retina regions of the eye . For cataract development, flavonols are suggested to play a role in modifying pathways causing eye lens opacification, including oxidative stress, epithelial function, nonenzymatic glycation, the polyol pathway, and lens calpain proteases . The antioxidant role of flavonoids such as flavonols has been linked to protecting and promoting antioxidant enzymes and inhibiting the function of the enzyme aldose reductase, which has a key role in the development of cataract among patients with diabetes .
One study reported a significant benefit of dietary flavan-3-ols in relation to AMD outcomes . According to Detaram et al. , lower intakes of dietary flavan-3-ols were significantly associated with poorer vision and almost double the risk of intraretinal fluid compared with higher intakes of flavon-3-ols. The lack of supporting evidence around the protective effects of dietary flavan-3-ols and anthocyanins for eye health may be due to their lower availability in the diet in comparison to flavonols , particularly the flavonol quercetin, which has been reported to be the most widely consumed and studied flavonoid .
Overall, there is a protective association between dietary flavonoids, particularly flavonols, and AMD, glaucoma, and cataract. However, for most of the sensory conditions included, only one study was identified. This signifies a strong need for further research in this area to substantiate any associations.