Rheumatic polymyalgia - a condition that almost always affects people over 50 years of age, in which case the immune system can cause muscle pain and stiffness, often across the shoulders and upper legs. It can also cause joint inflammation. Glasses, also known as eyeglasses or spectacles, are devices consisting of glass or hard plastic lenses mounted in a frame that holds them in front of a person's eyes, typically using a bridge over the nose and arms which rest over the ears. Glasses are typically used for vision correction, such as with reading glasses and glasses used for nearsightedness. Safety glasses provide eye protection against flying debris for construction workers or lab technicians; these glasses may have protection for the sides of the eyes as well as in the lenses. Some types of safety glasses are used to protect against visible and near-visible light or radiation. Glasses are worn for eye protection in some sports, such as squash. Glasses wearers may use a strap to prevent the glasses from falling off during movement or sports. Wearers of glasses that are used only part of the time may have the glasses attached to a cord that goes around their neck, to prevent the loss of the glasses.