Abstract
Primary open-angle glaucoma (POAG) remains a leading cause of irreversible blindness globally. Recent evidence further substantiates sustained oxidative stress, and compromised antioxidant defenses are key drivers in the onset of glaucomatous neurodegeneration. Overwhelming oxidative injury is likely attributed to compounding mitochondrial dysfunction that worsens with age-related processes, causing aberrant formation of free radical species. Thus, a compromised systemic antioxidant capacity exacerbates further oxidative insult in glaucoma, leading to apoptosis, neuroinflammation, and subsequent tissue injury. The purpose of this systematic review is to investigate the neuroprotective benefits of the macular carotenoids lutein, zeaxanthin, and meso-zeaxanthin on glaucomatous neurodegeneration for the purpose of adjunctive nutraceutical treatment in glaucoma. A comprehensive literature search was conducted in three databases (PubMed, Cochrane Library, and Web of Science) and 20 records were identified for screening. Lutein demonstrated enhanced neuroprotection on retinal ganglion cell survival and preserved synaptic activity. In clinical studies, a protective trend was seen with greater dietary consumption of carotenoids and risk of glaucoma, while greater carotenoid levels in macular pigment were largely associated with improved visual performance in glaucomatous eyes. The data suggest that carotenoid vitamin therapy exerts synergic neuroprotective benefits and has the capacity to serve adjunctive therapy in the management of glaucoma.
Highlights
Glaucoma is an optic neuropathy that is characterized by progressive neurodegeneration of the inner retina, including the optic nerve head (ONH) and retinal nerve fiber layer (RNFL), resulting in loss of retinal ganglion cells (RGCs) and characteristic visual field defects [1,2,3]
Observational clinical studies in this review were required to adhere to the following criteria: (1) studies evaluating the association between risk of open-angle glaucoma and carotenoid levels through dietary consumption of lutein and/or zeaxanthin or by validated clinical measurement of macular pigment optical density (MPOD) levels; (2)
While results from experimental models of glaucomatous injury indicate that the carotenoids lutein and/or zeaxanthin are sufficiently neuroprotective against neurodegeneration in the inner retina, there are some limitations to these findings that must be reviewed
Summary
Glaucoma is an optic neuropathy that is characterized by progressive neurodegeneration of the inner retina, including the optic nerve head (ONH) and retinal nerve fiber layer (RNFL), resulting in loss of retinal ganglion cells (RGCs) and characteristic visual field defects [1,2,3]. The body’s inherent defense mechanisms against oxidative damage, involving the neutralization of free radical species, rely upon the interplay between both endogenous and exogenous antioxidants to maintain redox homeostasis [21,33] Antioxidants such as the macular carotenoids lutein, zeaxanthin, and meso-zeaxanthin possess significant antioxidant and anti-inflammatory effects in the retina [34,35,36]. The difference in study findings mandates a need for a consensus and a summary-generating systematic review of the literature
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