We are commencing this paper with the portrait of a young lady who is perhaps the ultimate example of 'Extended Wear', in that her famous smile and enigmatic beauty has captivated the hearts of men since the fifteenth century. Her unique charms have indeed stood the test of time. The Mona Lisa is perhaps the most famous work of art of the Renaissance period, but this painting and its originator, Leonardo da Vinci, are not as far removed from the subject of contact lens wear as we may first imagine. Leonardo was responsible for a sketch showing the first outline of the principles of contact lens correction, the plan being drawn many centuries before its physical realization. From this principle, the concept was developed and enlarged upon through the centuries, first by the French philosopher and mathematician, Descartes, the English physicist, Young, and the astronomer Herschel. It was not until late in the nineteenth century that actual fittings were attempted by pioneers such as Muller, Fick, Sulzer, Galiewski and Mules. A limited success was achieved with early glass shells, wearing times of only half an hour being typical! From these early attempts, the development of glass haptic lens fitting continued steadily and in this context it would be unjust not to pay tribute to the great contribution of the late, Josef Dallos. With the introduction of plastic materials in the 1930's the use and fitting of haptic lenses became a little more commonplace. The first references we have been able to discover of extended wear, and for the purposes of this discussion we shall use de Caries definition of extended wear 'as greater than the twenty-four hour day', have been in an early text book by Frank Dickinson and K. Clifford-Halt, published in 1946. Three instances of extended wear are described. The first is a patient described as having worn his haptic lenses on two or three occasions for a period of three days and two nights without discomfort. The second, a lieutenant pilot, reported several daring exploits with his contact lenses. He proudly stated that he had had twenty-six days continuous wear during the invasion and conquest of Scicily in 1944. The third patient, a naval engineer, reported tolerences of twenty-four hours on numerous occasions. 'Even my girlfriend doesn't know', he said. Sometime later, he wrote from overseas, reporting, 'continued satisfaction even under adverse conditions'. Needless to say Dickinson and Clifford-Hall deprecated such wearing practices! Interestingly enough, quite recently, such a patient came into my care. He had been wearing his haptic lenses continuously for fourteen years! The result was far from satisfactory, with permanent corneal scarring and vascularization. The next major development in the evolution of the modern contact lens, was the micro lens of Kelvin Tuohy in 1948. These new corneal lenses again gave rise to more cited instances of extended wear, although many have proved to be somewhat apocryphal. Dickinson, again, describes an American Air Force officer who, when seen in 1953, had worn his corneal lenses for three months continuously. In 1960 David Sloane of Florida found that several of his patients were wearing their Polymethyl-Methacrylate corneal lenses for periods extending up to a month. He describes four patients who, having worn their lenses on an extended basis, 'had no evidence of corneal degeneration or fatigue'. Following these observations, Sloane fascinatingly describes how he himself wore bi-curve corneal lenses continuously for over a year. He tells of his own quite remarkable tolerence to them. From 1961, Dr. May, an optometrist in San Diego, California, reported continuous use of his own corneal lenses, and a period of at least nine years continuous wear was achieved in the course of his courageous research. May also cited a similar ex-