A cataract is much like a smartie or M&M. It has an outer coating (capsule) and an inner nucleus (the chocolate in the smartie). When an eye surgeon performs cataract/lens surgery the surgeon makes a circular opening in the front facing capsule of the lens and then removes the inner nucleus. The remaining capsular envelope supports the new artificial lens which is typically injected in through the opening in the capsule. Over time the capsule shrinks and wraps around the new lens much like shrink wrap or cling film.