Contact Lens Types
Todayís contact lenses have virtually eliminated the earlier hard lenses. Hard lenses were made from a material that didnít allow valuable oxygen to pass through to the cornea. They had to be small (to leave the cornea as uncovered as much as possible), and their size often made blinking uncomfortable and allowed the lenses to "pop out".
Todayís lenses are made from materials that allow oxygen to pass freely to the eye, allowing it to "breathe" comfortably. This enables todayís lenses to be bigger in diameter, greatly enhancing comfort and peripheral vision, whilst reducing the image distortion that can be caused by some spectacles.
Todayís lenses are made from two general types of materials:
Rigid Gas Permeable (RGP) Lenses combine some of the properties of both hard and soft lenses. Made of special firmer plastics, which are permeable to oxygen, these lenses are very durable and usually have a longer life span than soft lenses. Many people find them easier to handle than soft lenses. Like soft lenses, RGP lenses fit well and offer excellent visual acuity. RGP lenses are often prescribed for people who have high degrees of astigmatism. They take a little longer than soft lenses to get used to, but regular wearers find them very comfortable.
Most contact lenses are worn on a "daily-wear" basis. They are removed in the evening and put back in the next morning. Sleeping in your contact lenses is not advisable unless it is specifically recommended by your practitioner.
New advances in contact lenses have made it possible to have a fresh pair of lenses at regular intervals at about the same cost as wearing traditional daily-wear lenses. Frequent replacement programmes have become increasingly popular and also allow the contact lens wearer to spread the cost through monthly payments.
"Disposable" soft lenses are just what they say: after a prescribed period of time, the lenses are thrown away and replaced with a new pair.