A contact lens is a small transparent or opaque plastic device that covers the surface of the eye. Its purpose is to correct how light enters the eye to help you see better.

Many new contact wearers are concerned that a contact lens might become dislodged and get trapped behind the cornea. Fortunately, there is very little chance this will happen.

Soft Contact Lenses

Soft contact lenses are curved discs made of flexible, water-containing plastics called hydrogels. Hydrogels enable oxygen to flow through the lens and reach your cornea, allowing for clear vision.

These lenses can correct nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. If you have astigmatism, which causes blurry vision at both near and distance, a special type of soft lens called toric contact lenses can help.

Some types of soft contact lenses are designed to be worn and discarded on a daily, monthly or weekly basis. This allows for fresh, clean lenses and helps prevent build-up of protein deposits on the eye’s surface.

Rigid gas permeable (RGP) contacts are more durable and allow for more precise correction than soft contact lenses. However, they may not feel as comfortable, and require a longer period of adjustment. A new type of rigid contact lens that rests on the sclera (the white part of your eye) rather than the cornea is sometimes prescribed for conditions like keratoconus and other irregular corneas.

Hard Contact Lenses

Rigid gas permeable (RGP) lenses, or GP contact lenses, are often prescribed for people with hard-to-fit conditions. They allow oxygen to pass through the lens material and into your eye so that the cornea, or front clear dome of your eye, has a regular shape which improves vision.

Unlike older types of hard contacts which were made from polymethyl methacrylate, or PMMA, GP lenses are now mostly made from a more durable type of polymer called silicone hydrogel. They are more flexible than traditional hard contacts and they can be treated to be less rigid by a process known as plasma coating.

Despite their firm material, GP lenses can sometimes be damaged, especially when handled roughly or while wearing them during sports or other activities where the lens might move about. It is important that you keep your GP lenses clean and to replace them regularly. Also, you should avoid cleaning your GP lenses with tap water which may contain germs that can cause eye infections.

Bandage Lenses

Therapeutic bandage lenses protect the corneal epithelium from exposure, friction and irritation to encourage healing of the epithelial wound. They are a mainstay after refractive surgery procedures, including laser-assisted in situ keratomileusis (LASIK), laser-assisted subepithelial keratomileusis (LASEK), penetrating keratoplasty (PKP) and lamellar grafts, and also enhance epithelial recovery after eye injuries such as epithelial abrasions.

The contact lens industry has developed a range of silicone hydrogels that are well-suited for use as bandage lenses. They feature high oxygen transmissibility and low water content to avoid corneal edema, and a flat base curve that supports a shorter recovery time.

Mrs Hunter says that for people who have severe dry eyes, bandage lenses keep the eye-drops in their eyes longer and help them feel more comfortable. They can also reduce sensitivity to light. And for patients with keratitis, the protective lens can isolate tears around the injury to prevent them from coming into contact with the eye surface.

Contact Lens Examination

When first starting to wear contact lenses, it is important that the patient attend a contact lens evaluation in addition to their regular comprehensive eye exam. A contact lens evaluation will include a visual acuity test via a Snellen chart and a lens fitting, focusing on the health of the eye and the correct lens size for the individual. The doctor will also provide a trial pair of contacts and teach the techniques for proper insertion and removal of the lenses.

During the exam, the doctor may take additional measurements of the cornea using a computerized device called a keratometer and pupil and iris measurements. These tests will assure that the contact lenses fit correctly on the front surface of the eye, providing both good vision and comfort for the patient. The eye doctor may also decide to perform a tear film assessment, which determines whether the eyes are producing enough quality tears to prevent dry eyes from developing while wearing contacts