Contact lenses are now very commonplace, worn by over 100 million people. For most users, they are miracles. But they should be used with respect.
People get mislead by fads. For example, contact lenses to change eye color, or even make fantasy colors and shapes, have been extremely popular even with folks who do not need vision correction. But, such casual acceptance can cause vision problems.
If you have a good prescription for spectacles (“eyeglasses”), you are not yet ready to order contact lenses. Whether you are considering rigid lenses of some type or flexible contacts of another kind, there is more to consider than just the eye “refraction” or vision correction.
What about lens shape?
Do this experiment. Find someone with more than one set of eyeglasses, especially a person with large vision correction. Because clip-on sun shields can be a nuisance even if they are lightweight, and most are easily scratched, a person might have clear lens eyeglasses for non sunny wear, and tinted polarized spectacles for use in bright sunlight. Usually this means that the clear and sun lenses are made by different companies, even though the final adjustments are ground by the same local technician. Even though the vision correction is to be identical, the “base curves” of the original lens blanks can differ, which means the shape and thickness of the final lenses will not be the same. For large vision corrections, these differences will be obvious to visual or touch examination.
What does this mean about contact lenses? It’s a fact that there is no standard eye shape. Not only does shape vary with near and far sightedness, astigmatism, there also will be individual differences in the eye structure. The problem is like spectacle shapes all over again. Oh, and contacts also have to deal with eyelids. If the thickness and shape of a particular contact lens interferes with the eyelid, the wearer will either feel discomfort, or the contacts won’t even stay in.
So, simply ordering contacts to the prescription for spectacles can result in a very unsatisfactory wearing experience. The situation is no better if no vision correction is required, such as for colored contacts or fantasy lenses or theatrical effects.
Stupidity has no limits. Friends have exchanged contact lenses, especially for cosmetic coloration, as casually as they have swapped eye shadow and eyelash thickeners. This can result in rapid spread of serious eye infections. A badly infected eye can be unable to tolerate contact lenses of any kind, or even go blind.