Wednesday, October 08, 2008

Understanding contact lens induced dry eyes

The two types of contact lenses most often used today are soft lenses and rigid gas permeable (RGP) lenses. The softness in a contact lens comes from the amount of water that the lenses contain, and they feel pliable rather than hard. Because they provide more oxygen to the eye, people usually find them comfortable right away. RGP lenses are hard lenses that let in at least as much oxygen as do soft lenses.

A contact lens placed on the eye does not merely rest on top of the tear film but is immersed within it. The cornea, which usually receives direct oxygen from the atmosphere, now gets only diffused airing. Correct design and fitting of the lenses are essential for comfort, safety and accurate correction. Improvements in contact lenses have made them more comfortable and easier to wear.

People suffering from CLIDE usually have adequate tear quantity and quality under normal condition, however when eye is stressed- in this case, by the introduction of contact lens, may experience a symptomatic dry eye state. It is also believed that contact lens across the surface of the cornea may result in a less stable tear film and contact lens induced dry eye symptoms. A RGP lenses especially reduces blink rate leading to enhancing evaporation and leading to dry eyes. Contact lens induced dry eye also occurs in some people who may have had a marginally dry eye before they were fit with contact lenses or may actually be the result of contact lens wear.

Will dry eye affect eye sight?
Dry eye on its own should have no effect on vision; it does not cause permanent sight loss. There may be some temporary blurring of vision but this is normally relieved by blinking.

Marco’s comment:
Working class works 5 days a week and 8 hours a day, with consideration of travelling hours, one may have wear a contact lens for continuous more than 8 hours per day for 5 days in a week.

If you have dry eyes problem, try not wearing contact lens for more than continuously 4 hours a day.

Source: Health care booklet from Guardian pharmacy

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