For a long time, contact lenses came in two types – hard and soft. Soft lenses were more comfortable in the eye, but gas permeable hard lenses provided sharper vision. Now, these two lenses are being combined in a hybrid lens that offers the best of both worlds.
Soft contact lenses get their popularity from the comfortable fit allowed by their thin construction. These lenses tend to be large – covering not only the pupil and iris (the colored part of the eye) but also extending onto the sclera or white of the eye. Whether your eyes are open or closed, the edges of the soft contact lens are tucked under the edges of the eyelid. So when you blink, the lens doesn’t bump against the eyelid and it doesn’t try to lift off the eye.
The down side of soft lenses is also found in their thin construction. Because these lenses mold themselves to the shape of the eye, they are not able to hold to the rigid shape necessary to help your eye get the sharpest possible focus. As a result, soft lenses tend not to provide vision that is as clear as it could be.
Gas Permeable Lenses
Hard lenses area also known as gas permeable lenses because oxygen is able to travel through the lens to nourish the surface of the eye. These lenses are made of a more rigid plastic that does not bend, and are typically sized to be slightly smaller than the iris or colored part of the eye. As a result, these lenses float freely on the front of the eye. When you blink, the eyelid bumps against the edge of the lens then slides over the lens. This can cause irritation to the inside of the eyelid.
The advantage of gas permeable lenses is found in their harder construction. These lenses can be precisely manufactured to an exact prescription and will hold that prescription because the plastic of the lens does not change shape. This results in clearer, sharper vision.
The new, hybrid lenses offer the best characteristics of both hard and soft lenses. The center of a hybrid lens is made of rigid, gas permeable plastic that holds its shape and offers clearer vision.