Extended wear contact lens use

 
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Extended Wear Contact Lenses

Extended wear or continuous wear contact lenses are lenses that are worn overnight for continuous periods, normally of one to four weeks. Most extended wear lenses are worn continuously for up to a week. What distinguishes these lenses from other lenses is their high oxygen permeability.

What are the types of extended wear contact lenses?

Extended wear lenses have higher water content than other types of contact lenses. They are therefore classified according to their water content. They are classified into the following three types.

  • Higher water content lenses with water content of 70% to 80%. These lenses have the highest oxygen permeability but are less resistant to deposits and therefore get easily damaged.
  • Medium water content lenses with water content of 48% to 69%. These lenses are often the first choice in extended wear lenses.
  • Low water content lenses with water content of 38% to 45%. These are thin lenses and sometimes difficult to handle.

When are they used?

Extended wears contact lenses are favored by people who want to avoid the hassle of frequent removal or wearing of lenses. Such people could include those with naturally poor vision who are greatly handicapped without lenses or glasses. Groping in the night would be a big problem for them. They are also used by people, whose natural vision is not so poor, but prefer the convenience of extended wears. Extended wears are also used for cosmetic reasons.

What are the advantages of extended wear contacts?

  • Due to higher water content these lenses more easily conform to the shape of the cornea.
  • They have very high, almost 6 times oxygen permeability than other contacts. Given all things equal, chances of eye infections are less with these lenses.
  • Extended wears are very convenient especially for those with poor vision. This great convenience can be enjoyed by people who don’t want to handle lenses frequently.

What are the disadvantages of extended wears?

The convenience of extended wears comes with the inconvenience of more complications. The ideal extended wears must strike a balance between the convenience needs of the users and the safety needs demanded by practioners.

Some common complications are discomfort, dryness and dry eyes. These problems occur with other lenses also but their incidence is five times higher in extended contacts.

The reasons are obvious. Which are prolonged continuous wear, especially overnight wear, infrequent cleaning and reduced oxygen supply for long periods due to the cover provided by the lenses. Some organisms lodged under the lenses survive better in such conditions.

Initially they were approved for continuous wear up to two weeks. Approval for 30-day wear came shortly afterwards. But due to increasing complications, the approval was reduced to a week. Some practitioners went further and discouraged their patients from sleeping with extended contacts. The number of extended wear contact wearers went down.

Worn as they are, such complications with extended wears are unavoidable. Even the best of materials with the highest possible oxygen permeability will not be rid of these problems. At best the complications may be reduced.

What are the latest developments?

Disposable extended wears where the lenses are replaced every six or seven days were shown to be safer. These lenses reported fewer complications. A significant development was that fewer people discontinued extended wears. But disposable contacts did not lead to reduction in corneal ulcer cases.

Extended wears made from silicon hydrogel were introduced next. These lenses allow six times higher oxygen in to the cornea. In silicon-hydrogel lenses, higher water content increases oxygen permeability. The reverse is true in conventional soft contacts; higher water content causes lower permeability. Some practitioners began approving some brands, made from silicon hydrogel, for 30-day wear. Disposables were making a comeback.

To make these lenses safer still, improved lens designs and better cleaners and disinfectants are also being introduced.

What should I do to make extended wear safer?

  • Avoid smoke and swimming with lenses
  • Avoid sleeping with lenses if it is not too inconvenient
  • Immediately see a doctor if you have red or irritated eyes, reduced vision or any other discomfort
  • Follow your doctor’s instructions faithfully

Conclusion

Extended wear contact lenses offer great benefits. But they come with more complications. These are unavoidable but can be reduced. Improved materials, lens design and cleaners are being introduced. Meanwhile, you must strictly follow the doctor’s instructions about safety, usage and cleaning procedures.