The Materials That Go Into the Making of Contact Lenses

August 22, 2009 by  
Filed under Contact Lenses

The durability, wearing comfort, and effectiveness of contact lenses depend a lot on the materials of which they are made of. For pretty long, glass was the only material used for making contact lenses. However, 99% of contact lenses are today made of different types of plastics like polymethyl methacrylate or PMMA, or silicon hydroxy gel, or polycarbonate.

Hard contact lenses have been in use from 1960 onwards. These were made of PMMA. These contacts did not allow the passage of oxygen through the lens. But when a person blinks his eyes, there is naturally a slight movement of the contacts and this motion provided the scope for the passage of the air from the sides and underneath the lens permeating the tear solution around the eyeball.

Soft contact lenses came into use from 1971. This type of contact lens is hydrophilic, which means it can absorb water and newer models are quite permeable to air. These contact lenses are made of a polyacrylamide which contains HEMA or hydroxyethyl methacrylate. It is the presence of this compound which gives soft contact lenses its capacity for water absorption and thereby makes it more flexible and comfortable.

RGP or rigid gas permeable contact lenses are somewhere between hard contact lenses and soft contact lenses. In this PMMA of hard lenses are combined with fluoropolymers and silicone. The material ensures better oxygen supply to the eyeball and makes the user less prone to health risks related to contact lens use.

Silicon hydroxy gel is the material used in extended wear contact lenses. Its oxygen permeability is quite high and the user can keep the lenses on for quite long. Extended wear contact lenses may be designed to be worn for 2 days, or a week, or a month.

Disposable contact lens became common from 1987 onwards. Made of 58% water and 42% of a polymer by the name etafilcon, these contact lenses are flexible, fine, and well permeable to oxygen. They can be taken off daily and re-inserted or can be worn continuously for the prescribed time and then thrown away.

Disposable contact lens is a favorite of sports aficionados as it does not get displaced easily. Since they fit quite well, wearers are generally very comfortable with it. The downside is that vision correction may not be optimum with disposable contact lens. And some of these do not provide an absolutely clear sight. These make them unusable for many.

The selection in contact lenses is continuously widening. To start with, only single vision contact lenses were available. Today, bifocal contact lenses are available, the same way it is available for ordinary spectacles. There are also progressive lenses or multifocal contact lenses. Multifocal lenses are required for those with presbyopia, which is a form of farsightedness. Starting from those in their forties, many people develop this problem as they age.

Materials that go to form contact lenses and their varieties are continuously evolving. Your burden is only selecting the most suitable contact lens.