Sunglasses are worn to avoid direct bright sunlight that can damage or cause discomfort to the eyes. Continuous exposure to harmful UV radiations can damage eyes or retina. The use of sunglasses with a high eye protection factor (EPF) protects the eyes, especially from the rising effects of global warming. Sunglasses can be of two types - without prescription lenses (called Plano) and with prescription lenses (called Rx). The lenses used in sunglasses are usually made of polycarbonate, ADC, nylon, or glass. The frames are usually made of nylon, Zyl, plastic, and metal. However, new materials are also being commercialized such as polyamide materials which were brought to the market by a German glass manufacturer and designer company, Mykita. There are many styles and varieties of sunglasses available in the market. Some of the most popular styles are aviators, wayfarers, mirrored, and tea shades.