Choosing the right type of contact lenses is more complicated than selecting and buying glasses.

Although a few contact lens wearers still have old-fashioned hard lenses, most outlets currently supply only two basic types of lenses—soft lenses and rigid gas-permeable lenses.

Soft lenses, introduced in 1971, are made of a gelatin-like substance with high water content. Most wearers adapt to them quickly and easily. The high water content allows passage of oxygen to the cornea, the tissue covering the eye. This oxygen supply is crucial because the cornea, unlike other body tissues, doesn’t have a blood supply.

Current versions of rigid gas-permeable lenses, introduced in 1979, allow oxygen to easily pass through them. This feature, in turn, allows such lenses to be larger than old-fashioned hard lenses, which had to be small enough so that oxygen could pass around them to the cornea. The larger size makes them relatively comfortable because the eyelid doesn’t have to pass over the edge of the lens with each blink.

Soft lenses have several advantages over rigid lenses—

  • They are easy to get used to. You can wear them comfortably almost immediately, stop wearing them for days or even months, and then start again without an extended period of re-adaptation.
  • They are easy to fit. The softness permits some tolerance of variations in the cornea’s shape, so custom fitting is not required.
  • Because they cover a large part of the eye’s surface, they work well in dusty conditions where they prevent dust from reaching the eye.
  • They are not easily dislodged, making them ideal for use in sports.
  • They cost less.
  • With the availability of affordable disposable lenses, little or no maintenance is required.

On the other hand, rigid gas permeable lenses have important advantages over soft lenses—

  • They can provide clearer vision. Their rigidity allows precise shaping, which also means they can be used to correct serious astigmatism that standard soft lenses are unable to correct (however, special soft toric lenses are available for this purpose).
  • They are easier to clean because they are much less prone to collecting protein deposits. Ease of cleaning means regular maintenance is easier and cheaper, and you’re unlikely to suffer discomfort from wearing dirty lenses.
  • They are safer. Because they can be kept clean, they are less prone to harboring microorganisms that can infect the eye.
  • Because they don’t absorb moisture, they can be worn by individuals with relatively dry eyes.
  • They last longer than soft lenses because they don’t get as dirty and are harder to scratch. While soft lenses typically last for a year or less, standard rigid lenses generally last twice as long. However, lenses for extended wear (overnight) have shorter lifespans.
  • Their relatively long lifespans and ease of cleaning mean they are likely to cost less in the long run than soft lenses.

In terms of these two basic types of contact lenses, there are many variants—

  • Extended wear lenses. While regular lenses should be removed each night for cleaning and to allow oxygen to freely reach the cornea, extended wear lenses can have longer intervals between removals. Both soft and rigid gas-permeable extended wear lenses are available.
  • Disposable lenses. These soft lenses cost so little that you can afford to throw them away. Like other contact lenses, disposables are made in both daily wear and extended wear versions. Daily wear disposables, which must be removed and cleaned each day, are designed to be kept for a specific time period—two weeks, a month, or even three months. Extended wear disposables, designed to be worn continuously for one day or up to a month, depending on the brand, spare you the trouble of cleaning your lenses.
  • Additional options include lenses for astigmatism, bifocal lenses, tinted lenses, and UV-filtering lenses. There are also lenses with gas-permeable rigid centers that allow oxygen transfer and sharp vision, with soft perimeters for comfort. All these options cost extra.