Some carotenoids have vitamin A activity (so they can convert to retinol). These and other carotenoids can also act as antioxidants. In the eye, certain other carotenoids (lutein, astaxanthin, and zeaxanthin) apparently act directly to absorb damaging blue and near-ultraviolet light. This protects the macula of the retina, the part of the eye with the sharpest vision.