lens

n. 1. Any mechanism which refracts the light which passes through it in a symmetrical way. Convex lenses concentrate the light while concave lenses scatter the light 2. The transparent, convex structure in the front of the eye which focuses light on the retina and the fovea in particular, thus improving the clarity of vision. The lens in the human eye is stretched by the muscles of the eye to allow focus on objects of varying distance, further improving visual clarity.