What is a
A contact lens is a thin plastic lens placed directly onto the surface of the eye, usually to correct the vision. They can also be worn for therapeutic or cosmetic reasons.
Soft 'progressive' or 'multifocal' lenses have also been designed to help correct the effects of presbyopia, an age-related condition which leads to blurred vision when viewing near objects. They avoid the need for a pair of reading glasses.
Soft lenses - Soft contact lenses are flexible lenses that consist of different proportions of water. They tend to be made from hydrogel, silicon hydrogel or polymacon. They’re the most common choice of contact lens, as they are comfortable to wear and easy to care for. There are different types of soft lenses:
Disposable: daily disposable contact lenses are, as the name suggests, replaced every day – this means less cleaning, and less risk of infections such as conjunctivitis. Other disposable lenses are designed to be replaced every two weeks, monthly or every three months. These are worn on a daily-wear basis, to be cleaned after each use to prevent the risk of eye infection.
Rigid gas permeable lenses - Rigid gas permeable (RGP) contact lenses are very durable, some lasting for several years. They are less flexible than soft lenses, so can require time to get used to before they feel comfortable. They also require a thorough care routine to prevent infection. RGP lenses are better for correcting the effects of astigmatism, as they create a new refractive surface over the cornea.
Therapeutic lenses: People with a sensitive cornea may find standard contact lenses uncomfortable. If so, a scleral lens can be used. This is a larger RGP lens that rests on the sclera (the white area of the eye), covering the whole of the cornea. Scleral lenses can also be used for people recovering from eye injuries, and for conditions such as dry eye syndrome and keratoconus.
Cosmetic lenses: Coloured and ‘special-effect’ lenses are also available, and are often for used theatrical purposes. Cosmetic lenses can also mask eye injuries or disfigurements.