Carotenoids are natural
lipid-soluble
antioxidants abundantly found as colorful pigments in fruits and vegetables. At least 600
carotenoids occur naturally, although about 20 of them, including β-
carotene, α-
carotene,
lycopene,
lutein,
zeaxanthin,
meso-zeaxanthin, and
cryptoxanthin, are detectable in the human blood. They have distinct physiological and pathophysiological functions ranging from fetal development to adult homeostasis. β-
carotene is a precursor of
vitamin A that essentially functions in many biological processes including vision. The human macula lutea and eye lens are rich in
lutein,
zeaxanthin, and
meso-zeaxanthin, collectively known as macular
xanthophylls, which help maintain eye health and prevent ophthalmic diseases. Ocular
carotenoids absorb light from the visible region (400-500 nm wavelength), enabling them to protect the retina and lens from potential photochemical damage induced by light exposure. These natural
antioxidants also aid in quenching
free radicals produced by complex physiological reactions and, consequently, protect the eye from oxidative stress, apoptosis,
mitochondrial dysfunction, and
inflammation. This review discusses the protective mechanisms of macular
xanthophylls in preventing
eye diseases such as
cataract,
age-related macular degeneration, and
diabetic retinopathy. Moreover, some preclinical animal studies and some clinical trials are discussed briefly to understand
carotenoid safety and efficacy.