The contact lens history took a new dimension with the advent of lenses made from scleral plastic. Contact lenses may seem like a relatively recent invention but they were actually first proposed by Leonardo da Vinci. Indeed, the fact that early contact lenses were made of glass was a real limiting factor. They weren't just uncomfortable to wear – they were actually bad for the eyes if worn for any prolonged period of time. Lenses or prisms wear in front of the eyes for compensate different sight problems. The most usual shape of glasses is: a pair of glass lenses, in a metal or plastic frame and with the prop for nose. A good number of inventors or scientists have contributed to the evolution and modification of the concept behind contact lenses. Even now innovations haven't stopped and new models of contact lenses keep coming up. Colored contact lenses have given a different turn to the contact lens history.