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Q. What are the Contact Lens Materials ?
A. They are 3 contact lens materials :
1. Hard Lenses (PMMA) - Dk 0.0
Durable and easy to clean. Typically uncomfortable and related to long-term eye damage due to oxygen not reaching the eye. Today they're all but obsolete.
2. Soft Lenses (Hydrogel) - Dk 8-38
Made from a gel-like plastic, they will absorb 38-79% water and provide the eye with low to moderate amounts of oxygen. They offer initial comfort, but are prone to dehydration and to accumulating deposits, which can lessen comfort and require frequent replacement.
3. Oxygen Permeable Lenses (RGP) - Dk 12-150 and increasing !
Made from a firm, durable plastic that will transmit greater amounts of oxygen, they offer excellent vision and long-term eye health. Because they don't contain water, they resist deposits and aren't prone to harboring bacteria. This means they clean and disinfect easily, don't dehydrate, last longer, and are easy to handle. And like soft lenses, they offer the option of extended wear. Some adaptation is required; time varies from patient to patient.
Q. Can I wear RGP lenses ?
A. Visit your contact lens practitioner, he is the best person to perform an eye examination and advise you.
Q. What is the advantage of wearing rigid gas permeable lens, compared with wearing soft contact lens ?
A. Materials (e.g. Boston) of rigid gas permeable lens allows more oxygen flow to the cornea; that means, wearing rigid gas permeable lens is better than soft contact lens in terms of corneal health. Less ocular inflammation and edema has been reported. It is also more suitable for dry eye patients.
Q. Could astigmatism be corrected with rigid gas permeable lens ?
A. Since rigid gas permeable lens has 'tears' lens effect which can cover astigmatism more effectively when compared with wearing soft contact lenses. Therefore, rigid gas permeable lens wearers usually have clearer vision, compared with wearers of spherical soft contact lens.
Q. Does rigid gas permeable lens easily come off ?
A. Rigid gas permeable lens is stabilized over the eyes by the adhesion effect of tear. A good fit rigid gas permeable lens does not easily come off, even during blinking.
Q. Could rigid gas permeable lens wearers rub their eyes ?
A. Eyes rubbing is always discouraged under any circumstances. Because of the rigidity of gas permeable lens material, vigorous lens movement over the cornea would cause corneal damage.
Q. Why do patients sometime feel the rigid gas permeable lens in initial wearing ?
A. Patients sometime feel the lenses because the lenses are made of rigid gas permeable lens material. For first contact lens wearers, they are advised to look downwards for better comfort. After a week of adaptation, lens awareness is largely reduced and will be appreciated by patients.
Q. Can RGP lenses be worn overnight ?
A. Yes. The Boston XO Lens (or other Extended Wear RGP) can be worn for overnight. Seek your contact lens practitioner for advice.
Q. How to clean rigid gas permeable lens ?
A. Cleansing of rigid gas permeable lens is easy. After lens removal, patients only need to rub the lenses with cleaner and soak them into disinfecting solution. Less frequent use of protein remover is needed.
Q. Is wearing rigid gas permeable lens more expensive than wearing soft contact lens ?
A. Although rigid gas permeable lens is a little bit more expensive than soft contact lens, it is more durable than soft lens. In other words, replacement of rigid gas permeable lens is less frequent than that of soft contact lens.
Q. What does the UV inhibitor and tinted lens have in advantage ?
A. The combination of a UV light inhibitor and tinted colour gives additional protection from harmful sunlight. Trials showed, however, that UV-Soft ontact lenses further eliminate the disturbing effects of passing abruptly from bright ambient light into dark environments and vice versa.
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