Introduction Unlike soft lenses, which drape to fit the cornea so that on the eye the geometry of the back surface closely conforms to that of the anterior cornea, the back surface of a rigid lens (corneal, corneoscleral or scleral)…
Introduction Although lathing technology has been used to fabricate contact lenses since their invention over 130 years ago, developments over the past quarter of a century in precision engineering, materials technology and computer control systems have resulted in a capability…
Introduction Rigid lens materials have played an important role in the development of rigid contact lenses generally and occupy a small but significant place in the range of currently available products. Much of the relevant information is contained in the…
Introduction With the very notable exceptions of daily disposable lenses and extended-wear lenses that are discarded after each period of continuous wear, all contact lenses must be subjected to some form of maintenance procedure after each use. The key elements…
Introduction The use of soft toric lenses (in preference to spherical soft lenses) is indicated when there is ocular astigmatism present, be it corneal or noncorneal, that warrants correction. Unlike rigid lenses, soft lenses do not mask corneal astigmatism but…
Introduction Assessment of soft contact lens fit is probably the most commonly undertaken task in contact lens practice but is also one of the least discussed, possibly because it is regarded as a relatively straightforward exercise. However, soft lens fitting…
Introduction The vast majority of soft contact lenses are today mass produced by a double-sided moulding process (see Chapter 5 ). Using such a method of manufacture ensures relatively consistent quality, eliminating the need to measure every lens that comes…
Introduction Single-vision soft contact lenses have a number of optically attractive features. They centre well on the cornea with only small amounts of lateral movement and hence introduce little additional asymmetric aberration into the lens–eye system. The diameter of their…
Introduction Three techniques are currently employed to manufacture soft contact lenses – lathe cutting, spin casting and cast moulding. A fourth disruptive technology, three-dimensional (3-D) printing, has also been proposed, but 3-D-printed soft contact lenses have yet to be produced…
Introduction Soft contact lenses have had a massive impact on the global contact lens market since they became widely available in the early 1970s. Since their introduction, the number of soft contact lenses being prescribed around the world has steadily…