Tips to Use Contact Lenses

Corrective contact lenses A corrective contact lens is a lens designed to improve vision. Conditions correctable with the contact lenses include short sightedness(Myopia), far sightedness(Hypermetropia), astigmatism and presbyopia. Cosmetic contact lenses These lenses are designed to change the appearance of the eye.

Therapeutic contact lenses Soft lenses are often used in the treatment and management of no n refractive disorders of the eye. A bandage contact lens protects an injured or diseased cornea from constant rubbing of blinking eye lids thereby allowing it to heal. Types of contact lenses by material The first contact lenses were made of glass, which caused eye irritation, and so were not able to be worn for extended periods of time. The introduction of lenses made from polymethyl methacrylate(PMMA) becomes much more convenient and these lenses are commonly referred as "Hard" lenses. However PMMA lenses doesn't transmit oxygen to the cornea which can cause a number of adverse clinicle events.

In the late 1970 improved rigid materials which were also oxygen-permeable were developed. These lenses were referred as RGP lenses. In effect, the lens is able to replace the natural shape of the cornea with a new refracting surface and provides good level of vision in people wgo have astigmatism or distorted corneal shapes as with keratoconus. The principle breakthrough in soft lenses made by Otto Wichterle led to the launch of the first soft lenses in the 1980's. Soft lenses are immediately comfortable, while RGP lenses require a period of adaptation. The polymers from which soft lenses are manufactured improved over the next 25 years, primarily in terms of increasing the oxygen permeability. In 199, silicone hydrogels became availabkle. Silicone lenses have extremely high oxygen permeability and were advocate primarily for extended(overnight) wear.  A daily wear lenses is designed to be removed prior to sleeping. An extended wear(EW) lenses is designed for continuous overnight wear, typically for 6 or more consecutive nights. Newer materials such as silicone hydrogels allow for even longer periods of up to 30 consecutive nights, these lenses were referred as continuous wear(CW). The various soft contact lenses available are often categorized by their replacement schedule.More commonly contact lenses are prescribed to be disposed of on a two week or monthly basis. Quarterly or annual lenses, which are used to be very common, have lost favor because a more frequent disposal schedule allows for thinner and limits deposits. Complecations due to contact lenses wear affect roughly 5% of contact lens wearers each year. Excessive wear of contact lens, particularly overnight wear. Problems associated with contact lens may affect the eyelid, conjunctiva and the v