are a very safe vision technology, when they are properly fitted, prescribed, and monitored by your eye doctor
. The act of wearing contact lenses does not make your vision deteriorate. Of course, there is general slow deterioration of vision with aging, but this also occurs in people who wear glasses (and even in those who don't!).
Most of the problems with contact lenses that wearers experience arise when they are not worn properly or when they are not cleaned properly. For example, wearing contacts beyond their expiration date can lead to the build up of protein deposits on the lenses, which can cause scarring or scratching of the corneas of the eye. Similarly, not cleaning contact lenses as recommended by the manufacturer or your eye doctor can increase your risk of eye infections from bacteria and fungus. These infections can sometimes cause serious damage to vision, including blindness.
However, as already mentioned, these complications are very unlikely as long as you regularly see your eye doctor and as long as you use your contact lenses only as directed. Of course, if you experience any redness, blurry vision, or pain while using contacts you should see your eye doctor immediately.