There are two principal types of contact lenses in use today. Soft contact lenses are those that are made of hydrophilic plastics and absorb liquid and must be kept moist for softness and easier moulding to the corneal surface. They are extremely comfortable and are used by majority of contact lens users. The other type in use is the gas permeable (RPG) or rigid contact lenses, which are composed of durable and flexible plastics, which permit oxygen to pass through to the cornea and are easier to maintain. The original hard lenses, or PMMAs, used earlier did not allow oxygen to pass to the eye and have been replaced by the RPGs.
If a person desires to use contact lenses, he or she should do so only after consultation with an ophthalmologist. He/she will advise whether contact lenses would be suitable for a person to use or which kind of lenses, soft or gas permeable, should be used in a particular case. It is imperative that a yearly examination be done after the initial use of contact lenses.
Courtesy- contactlensdoctor.com/
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