Sunglasses allow better vision in bright daylight, and may protect one's eyes against damage from high levels of ultraviolet light. Typical sunglasses are darkened for protection against bright light or glare; some specialized glasses are clear in dark or indoor conditions, but turn into sunglasses when in bright light. Most sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be ordered. Specialized glasses may be used for viewing specific visual information (such as stereoscopy) or 3D glasses for viewing three-dimensional movies. Sometimes glasses with no corrective power in the lenses are worn simply for aesthetic or fashion purposes. Even with glasses used for vision correction, a wide range of designs are available for fashion purposes, using plastic, wire, and other materials. Macroeconomics' need for government intervention ' In management, the plan has a double meaning, one is the work plan, is refers to according to the analysis of external environment and internal conditions, put forward in the future a certain period of time to achieve organizational goals and achieve the goal of the solution way. Secondly, plan form, it is to point to in words and index within the organization of the form of expression and organization of different departments and different members of a certain period of time in the future about the management of the direction, content and way to arrange events.