Lutein and zeaxanthin, found together in many vegetables, are potent antioxidants. They occur in high concentrations in the eye, including the lens, retina, and macula. For that reason, lutein and zeaxanthin are thought to be crucial to healthy vision.
Eye-related benefits: Lutein and zeaxanthin protect the eyes from harmful high-energy light waves, such as some ultraviolet rays in sunlight. Studies suggest that high levels of lutein and zeaxathin in eye tissue are associated with better vision, especially in dim light or where glare is a problem. Diets rich in these two antioxidants appear to protect against age-related eye diseases. For example, one study found that people with diets high in foods rich in zeaxanthin -- particularly spinach, kale, and broccoli -- are up to 50% less likely to develop cataracts. A major study (called AREDS2) has shown supplements containing lutein and zeaxanthin can slow the progression of macular degeneration if you already have it. A test called macular pigment optical density is now being used by eye care specialists to measure levels of lutein and zeaxanthin in eye tissue.
Most of the focusing power in the eye occurs along the front surface, at the cornea (the clear 'window' in the front of the eyeball), or within the lens, which sits behind the cornea inside the eye. The ideal cornea has a symmetrically curved surface, like a basketball. Astigmatism is caused by a cornea or a lens that is not symmetrical, like a football.
The cornea is the transparent window in front of the colored part of the eye. It bends (refracts) light rays to focus the light onto the retina...