Treatment: Glasses and Contact Lenses

Most refractive errors can be corrected by wearing glasses or, for older children and adults, contact lenses. Glasses are suitable for most refractive errors, are comfortable to wear, and do not cause complications. Contact lenses are also available for many refractive errors, but they are most effective for myopia and hypermetropia. Nondisposable contact lenses require careful cleaning to reduce the chance of an infection of the transparent cornea over which they are placed.

How lenses work

Glasses and contact lenses correct refractive errors in the eye by altering the angle of light rays before the rays reach the surface of the cornea, the transparent front part of the eye. The cornea at the front of the eye and the lens can then focus the rays correctly on the retina. Concave lenses make the light rays diverge (bend apart) and convex lenses make the light rays converge (bend together).

Myopia and hypermetropia

Myopia is corrected by concave lenses, which make light rays diverge and focus on the retina, not in front of it. Hypermetropia requires a convex lens to make light rays converge, focusing them on the retina and not behind it.

Contact lenses

There are three main types of contact lenses: rigid, gas-permeable, and soft. Soft lenses are the most widely used and rigid the least. Some soft lenses are worn only once or for a few days. Nondisposable lenses should be disinfected daily unless worn for an extended period (not usually recommended). If an eye becomes red or painful, you should stop wearing your lenses and consult your optician immediately.

Rigid and soft lenses

A contact lens floats on the tear film on the front of the eye. Soft lenses cover the whole cornea; rigid and gas-permeable lenses cover only the central part of the cornea.

Contact lens care

Good lens hygiene prevents eye infections. Nondisposable lenses must be carefully cleaned before and after use and soaked overnight in disinfectant solution.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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