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Hard Contact Lenses


Hard contact lenses are generally known as semi-rigid gas permeables (RGPs)and they are now made of plastic-like material, although originally they were in fact made of glass. For many years, hard contact lenses were made out of a material called polymethyl methacrylate (PMMA). These contact lenses tended to be uncomfortable because they allowed no air passage. Though designed to move slightly during each blink, to allow for the proper oxygenation of tears, more blinking was required for the eye to be properly lubricated and aerated. Most types of RGP lenses now incorporate silicon, which makes them more flexible than the old PMMA contact lenses. Although they are 'hard' they have some flexibility, about the same as that of the bendy part of a plastic spoon. Wearers of these lenses are aware of them all the time, although the sensation may diminish over time. RGP lenses are custom fitted to the shape of your cornea. Since they are rigid, RGP contact lenses retain their shape better than soft contact lenses and therefore provide crisper vision. They are also more durable than soft lenses, which can tear easily. RGP lenses are made of materials that do not contain water, which means a single pair can last for years with proper care and maintenance. In addition, their ability to be custom manufactured enables RGP contact lenses to correct a wider range of vision problems than soft contact lenses can. The advantage of hard contact lenses is that the vision is high quality and they can control the progression of nearsightedness to some degree. The disadvantages are that the lens is not as comfortable to wear as the soft lenses, and they may fall out more frequently. Also, a person wearing RGP lenses who decides to wear prescription eyeglasses for a few days will find their eyes are no longer acclimated to the use of the rigid contact lenses. For consistent comfort, RGP contact lens wearers have to wear their contact lenses on a daily basis and this is not ideal for everyone.