The lens is a transparent, avascular biological structure that lacks a cell nucleus upon maturity. Its transparency depends on the precise organization of its structural proteins—the crystallins (α, β, γ). Cataracts result from the gradual clouding of these proteins due to cumulative oxidative stress: free radicals (generated by UVB radiation, smoking, and diabetes) oxidize the cysteine residues in the crystallins, causing them to aggregate irreversibly. Phacoemulsification surgery—replacement of the clouded lens with an implant—is currently the only curative treatment. Dietary supplements are intended solely for prevention and to slow the progression of the condition.
Vitamin B2 (riboflavin) is a fundamental cofactor for lens health. It is essential for glutathione reductase—an enzyme that regenerates reduced glutathione (GSH) in the lens epithelium. Glutathione is the most concentrated antioxidant in the lens (up to 10 mM) and serves as its first line of defense against free radicals. Epidemiological studies (Hankinson et al., 1992; Jacques et al., 2005) show that low riboflavin intake is associated with an increased risk of nuclear and posterior subcapsular cataracts. An intake of 1.1 to 1.6 mg/day is sufficient to maintain optimal activity of lens glutathione reductase.
As the most potent red carotenoid against the singlet oxygen radical (¹O₂)—the primary reactive species generated by UVB in the lens— lycopene accumulates preferentially in the lens itself, according to tissue assay studies. Case-control studies (Mares-Perlman et al., 1995) associate low serum lycopene levels with an increased risk of cortical and nuclear cataracts. The best dietary sources are cooked tomatoes (free lycopene is 3 to 5 times more bioavailable than in raw tomatoes), pink grapefruit, and watermelon.
The epithelial cells of the lens—the only living cells in the lens—rely on mitochondrial activity to maintain the ion pumps (Na⁺/K⁺-ATPase) that preserve lens transparency. Coenzyme Q10 is the mitochondrial electron carrier essential for this ATP production. Animal models show that CoQ10 significantly reduces cataract formation. Its concentration in the human lens decreases with age and in diabetic patients—a population at high risk for posterior subcapsular cataracts.
Several age-independent factors accelerate lens opacification. Smoking increases the risk by a factor of 2 to 3 by depleting lens glutathione. Uncontrolled diabetes activates the polyol pathway in the lens, leading to the accumulation of sorbitol, which disrupts lens osmolarity and structure. Prolonged exposure to UVB rays without sunglasses accelerates the photooxidation of lens proteins. Long-term systemic corticosteroid therapy is associated with posterior subcapsular cataracts. A diet rich in antioxidants and wearing UV-protective sunglasses are the best-documented preventive measures.
Before surgery, antioxidant supplements (lycopene, CoQ10, riboflavin, AREDS-type formulas) slow the progression of opacification without reversing an established cataract. After surgery, the natural lens is replaced by a synthetic implant that can no longer become cloudy. Antioxidant supplementation remains important for protecting retinal structures—justifying the continued use of a comprehensive eye supplement after surgery. The “Retina” page and the eye comfort supplements available on our website provide guidance on formulas suited to each situation.
