Dietary Antioxidants, Macular Pigment, and Glaucomatous Neurodegeneration: A Review of the Evidence

Abstract

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness worldwide, and the prevalence is projected to increase to 112 million worldwide by 2040. Intraocular pressure is currently the only proven modifiable risk factor to treat POAG, but recent evidence suggests a link between antioxidant levels and risk for prevalent glaucoma. Studies have found that antioxidant levels are lower in the serum and aqueous humor of glaucoma patients. In this review, we provide a brief overview of the evidence linking oxidative stress to glaucomatous pathology, followed by an in-depth discussion of epidemiological studies and clinical trials of antioxidant consumption and glaucomatous visual field loss. Lastly, we highlight a possible role for antioxidant carotenoids lutein and zeaxanthin, which accumulate in the retina to form macular pigment, as evidence has emerged supporting an association between macular pigment levels and age-related eye disease, including glaucoma. We conclude that the evidence base is inconsistent in showing causal links between dietary antioxidants and glaucoma risk, and that prospective studies are needed to further investigate the possible relationship between macular pigment levels and glaucoma risk specifically.

Epidemiology of Glaucoma: The Past, Present, and Predictions for the Future

“…The direct costs of glaucoma include medical bills, cost of medications, and transportation costs while indirect costs include low productivity at the workplace and days missed from work [ 17 ]. Furthermore, the burden of glaucoma extends to the families of patients, the healthcare system, and society at large [ 18 - 19 ].…”

“…Comparatively, the economic burden of glaucoma alone on the American economy is $2.9 billion [ 3 ]. The cost of treating and preventing glaucoma is about $5.8 billion per year in the US with the annual medical cost of glaucoma projected to be as high as $12 billion by 2032 and $17.3 billion by 2050 [ 18 - 19 ]. The annual direct cost of glaucoma treatment in the US ranges from $623 to $2,511 depending on its severity [ 21 ].…”

Bioactive Properties of Carotenoids in Human Health

“…Based on the authors’ bibliographical research, a causal relationship between the risk of developing glaucoma and the consumption of antioxidants has not yet been established. However, as they point out for some preclinical studies, it is possible that lutein supplementation and zeaxanthin supplementation have some beneficial effects on this disease that deserve further study [12].…”

Targeting Diet and Exercise for Neuroprotection and Neurorecovery in Glaucoma

“…Additional nutritional factors are likely of great importance for systemic health, as well as retinal and optic nerve health, in glaucoma. The role of different antioxidants (e.g., vitamins A, C, and E; omega 3 and 6; co-enzyme Q 10 ; resveratrol; and green tea extract) have been well explored in animal models and are reviewed in detailed elsewhere, with a general trend for mild to moderate neuroprotective effects in isolation and in combination formulations [ 142 ]. A number of clinical trials and association studies have been performed to assess antioxidant capacity/dietary intake or antioxidant treatment in glaucoma [ 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 ].…”