What is contact lens
Contact lenses are devises used to correct the visual acuity of the person wearing them. These modern day contact lenses are almost invisible due to their transparent nature. These lenses are placed directly on the eyes. The most commonly used contact lenses are soft lenses. The contact lenses can be used both for correcting the vision and also for cosmetic purpose. Contact lenses are more convenient to use than glasses due to a number of reasons. It is imperative that one visits an eye care specialist to do a thorough check before putting on the contact lenses.
A chemist named Otto Wichterle was responsible for inventing the modern contact lenses. Otto was helped by his assistant Drahoslav Lim who also helped develop the gel which is used for the production of the contact lens. These contact lenses are transparent, may bear a slight color at times, and are extremely light weight. The contact lenses are placed upon the cornea of the eye, directly in front of the iris. The contact lenses correct the refractive error of the human eye.
Contact lenses are sometime deliberately colored for ease of detection during cleaning and storage, since they are transparent. Many people wear the contact lenses for cosmetic purposes, these lenses are colored. One of the major advantages of using the contact lenses is that they ensure a wide field of visibility as compared to glasses. Extreme care has to be taken during storage and usage of the contact lenses. Any particulate matter can cause irritation to the eye; hence proper precaution needs to be taken.
There are usually two types of contact lenses, in terms of the material that they are made of, hard and soft contact lenses. Hard contact lenses utilize polymethyl methacrylate (PMMA) and are rigid in nature. The soft contact lenses are usually made of hydro gels which are soft to touch. The first contact lenses were made of glass, and then the PMMA were discovered, however, the PMMA developed initially, was impermeable to gases exchange. Then the oxygen permeable rigid lenses were developed. In the 1960’s the soft polymeric material were developed which had oxygen permeability. The advent of silicone hydro gels increased the performance and comfort of the soft lenses.
In terms of the wear time, the contact lenses can be categorized as daily wear, extended wear and continuous wear. The daily wear contact lenses need to be removed while sleeping. The extended wear (EW) lens can be worn overnight and the continuous wear (CW) contact lenses can be worn for almost 6 days at a stretch. The continuous wear lenses needs to be discarded after a certain period of time.
The contact lenses can also be categorized depending upon how long they can be used. Some are for only 24 hours usage; some are to be used only for a week or a month. Some lenses need to discarded after a quarter and finally, there annual usage contact lenses.
Contact lenses are more convenient as compared to glasses and are extremely light. They are used for refractive correction and accentuating the beauty. These contact lenses are of the rigid and soft types, soft types are more popular. Contact lenses can be of a single use to types which can be used for one year. Contact lenses are placed directly on the cornea for usage.