The sunlight-related diseases have different symptoms and affect different parts of the eye. Cataract is a cloudiness of the lens. Macular degeneration destroys the central part of the retina. Cancer of the circumocular skin, pterygium and photokeratitis are afflictions of the front of the eye. Having estabilished that sunlight was the source of these eye diseases, vision scientists set out to learn what parts of sunlight were hazardous.
Sunlight is radiation-pure, radiant energy.
There is a range or spectrum of energy particles-low energy in the infrared, more energy rising continuously through the visible spectrum through the red, orange, yellow and green, high energy in the blue and violet and highest of all in the invisible ultraviolet. Ultraviolet radiation proved to be the cause of all the sunlight-related eye diseases axcept for macular degeneration. The retina of eye, the site of macular degeneration , was spared ultraviolet radiation's deleterious effects because UV is absorbed in the anterior part of the eye, where it causes the sunlight-related eye diseases situated there. It is the high energy violet and blue part of the sunlight spectrum that proved to contain the radiation that harms the retina. The good news is that protection against all of these devastating eye diseases can be achieved simultaneously without disturbing normal vision, simply by using the right kind of sunglasses.