Contact Lenses
Contact lenses are thin, curved plastic discs covering the cornea and designed to correct your vision. Due to the surface tension, contact lenses cling to the film of tears over the cornea. Contacts offer a good alternative to eyeglasses, depending on your eyes and your lifestyle.
Contact lenses correct the same conditions that eyeglasses correct like Myopia (nearsightedness), Hyperopia (farsightedness), Astigmatism (distorted vision) and Presbyopia (need for bifocals). Additionally, contact lenses are used therapeutically in eye diseases such as keratoconus or scarring where an uneven cornea blurs vision. Certain tinted contact lenses can be used to change the color of the eyes as well.
There are two main categories of contact lenses – Soft lenses and Gas Permeable lenses. Ensure that you decide upon the lens only after consultation with the eye care practitioner.
Rigid or hard contacts were the first lenses developed in the 1960's. They are made of a type of plastic called PMMA (polymethyl methacrylate), which though strong and resilient does not allow the passage of oxygen in to the eye. The lens moves with the blinking of the eye allowing oxygen dissolved in the tears to reach the cornea. Rigid lenses are the least comfortable type of contacts and are not really used anymore.
Gas-permeable lenses: These lenses are also known as Rigid Gas Permeable Lenses. They are newer rigid lenses made of plastics combined with other materials, such as silicone and fluoropolymers, which allow oxygen in the air to pass directly through the lens. And that is why they are known as gas permeable.
Soft contact lenses: These lenses are made of plastic materials that include water. The water makes them soft and flexible, as well as allows oxygen to reach the cornea. More than 75% of contact lens wearers use soft lenses. Under this category are a few more variety of contact lenses:
- Extended wear contact lenses which are made such to last 2-4 weeks.
- Daily disposable lenses – are changed daily. A little on the steeper side as far as cost is concerned, they are generally low in risk due to infections. Toric contact lenses are used to correct moderate astigmatism. They are available in both rigid and soft materials.