The concept of a contact lens was first thought up by Leonardo da Vinci in 1508. For centuries the idea of contact lenses captured the scientific and medical imagination, but it was not until the early 1970s that modern materials were developed to make them comfortable enough for people to actually use. Today, contact lenses are more comfortable, more durable, and last longer than ever before. If you are unsure which contact lenses are the right choice for you, here is a comparison between hard and soft contact lenses.
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.
Soft Contact Lenses
People choose soft contact lenses as they are ultra-comfortable when worn. In fact people do not even notice they are wearing them. Soft lenses are made of plastic-like material but their flexibility is rather like Sarin wrap used on foods. With the latest modern technology, soft contact lenses come in just about any type of correction you can think of. They can be supplied in colors too. Best of all soft contacts come in disposable varieties, which require no special maintenance such as the use of chemical cleaning solutions. You simply wear them for a day and then throw them away. Soft contact lenses are so called because they absorb water. The water content of a soft contact lens at full saturation can vary from 37 to 80 percent. Soft contact lenses that contain a higher concentration of water can stay in the eye comfortably for longer periods of time and are usually marketed as extended wear lenses. For many years soft contact lenses were considered a significant innovation in contact lens technology. They were smaller and thinner than their hard contact lens predecessors, and they provided clear vision to thousands of people who found it too uncomfortable to wear hard lenses. Although soft contact lenses are still the most common variety of contacts, with the advent of new RGP lenses, there is no longer a consensus as to their superiority. Soft lenses do, however, possess certain advantages over the newer generation of hard contacts. Soft contact lenses are immediately more comfortable to wear than RGP lenses, which require an extended period of time for the eyes to adjust to them. For this reason, soft contact lenses also allow for more flexible wear. A person who wears both contact lenses and eyeglasses can freely switch between soft contacts and eyewear without a loss in comfort levels. On the downside, soft contact lenses easily absorb remnants of soap and lotion from your hands, causing irritation in your eyes. Proteins and lipids will eventually adhere even to non-disposable soft contact lenses, necessitating replacement lenses.
Common Factors for soft and hard contact lenses
Both types of contact lenses are very easy to use and handle. The two things to avoid are: wearing contact lenses whilst sleeping and wearing the lenses more than the recommended schedule. If you follow the proper procedure and care for the contact lenses, it is unlikely that you will have any problems with infection.
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