When cataract surgery is performed, the surgeon must remove the cataract from the capsular bag. Think of it as removing the chocolate from an M&M but leaving behind the candy coating. Sometimes the capsular bag can turn cloudy, resulting in a loss of vision. This is called a secondary cataract or posterior capsular opacification (PCO). Although rare, they do occur within the first few years following cataract surgery. A secondary cataract is not a cataract at all. Secondary cataracts can be corrected by performing a simple laser procedure called a yag capsulotomy. The procedure uses a yag laser, in which the surgeon makes a small opening in the capsular bag, instantly restoring vision.