All eyeglasses lens are able to reflect some light, reducing the amount of light that enters the eyes to form visual images. In this way, it can affect your vision, especially under low light conditions, for example, driving at night. Moreover, lens reflections also cause glare, further reducing vision in these situations. Generally, the amount of light reflected from eyeglasses lenses depends on the lens material. Plastic lenses reflect about 8 percent of incident light, so 92 percent of available light enters the eye for vision. Thinner, light high index lenses such as polycarbonate lenses reflect up to 50 percent more light than regular glasses or plastic lenses. So they can cause problems with glare unless something is done to reduce reflections.