they are flatter and lighter than conventional lenses.there are many lenses and lens-coating lenses options for individual needs, including coatings sfx that block the theatrical ultraviolet (uv) light or uv and blue light which have been found to be harmful to the eyes. such coatings are not needed on polycarbonate lenses, which already have uv protection. uv coatings are particularly important on sunglasses and ski goggles. sunglasses, when nonprescription, should be labeled with an indication that they block out 99-100% of both uv-a and uv-b rays. there are anti-scratch coatings that increase the surface hardness of lenses (an important feature when using plastic lenses) and anti-reflective (ar) coatings that eliminate almost all glare mirror and allow other people to see the eyes of the wearer. ar coatings may be particularly helpful to people who contact use computers or who drive at night. mirror coatings that prevent other people from seeing lenses the wearer''s eyes are also available. there is a whole spectrum of tints, from light tints to darker tints, used in sunglasses.

they are flatter and lighter than conventional lenses.there are many lenses and lens-coating lenses options for individual needs, including coatings sfx that block the theatrical ultraviolet (uv) light or uv and blue light which have been found to be harmful to the eyes. such coatings are not needed on polycarbonate lenses, which already have uv protection. uv coatings are particularly important on sunglasses and ski goggles. sunglasses, when nonprescription, should be labeled with an indication that they block out 99-100% of both uv-a and uv-b rays. there are anti-scratch coatings that increase the surface hardness of lenses (an important feature when using plastic lenses) and anti-reflective (ar) coatings that eliminate almost all glare mirror and allow other people to see the eyes of the wearer. ar coatings may be particularly helpful to people who contact use computers or who drive at night. mirror coatings that prevent other people from seeing lenses the wearer''s eyes are also available. there is a whole spectrum of tints, from light tints to darker tints, used in sunglasses.

originally, hard contact sfx were made of a material called pmma. although theatrical still available, the more common types of contact are listed below:rigid gas-permeable (rgp) daily-wear lenses are made of plastic mirror that does not absorb water but allows oxygen to get from the atmosphere to the cornea. (this is important because the cornea has no blood supply and needs to get its oxygen from the atmosphere through the film of tears that moves beneath the lens.) they must be removed and cleaned each night. rigid gas-permeable (rgp) extended-wear contact lenses are made from plastic that also does not absorb water but is more permeable to oxygen than the plastic used for daily-wear lenses.