Contacts, I believe, were developed in order to allow the visually impaired public to avoid glasses. Why? Glasses are hard to clean, scratch easily, get stepped on, run over by vehicles and most importantly can be nerdy.
Contact lens wearers often swear by them. After all, no glasses and well, you can see. You can even change the colors so that your eyes now appear a sexy blue rather than a nondescript brown. Many of the contacts are disposable, which makes it easier to justify losing one or two.
Still, contacts have issues, some of which are serious. Contacts are cleaned with a solution. Some wearers have allergies to this solution and develop itchy, red eyes. At times the solution may lose its sterility and transfer nasty bugs to the contacts. Wearing these contacts, especially extended wear contacts, can then cause infections of the coverings of the eye. Diabetics are especially prone to these complications. Infected eyes are painful, red and have a discharge. Rare cases of serious eye infections (endopthalmitis) may even cause permanent blindness.
Sometimes contacts may be malfitting or left on too long. In either case, breakdown of the corneal surface (the part of the eye where the contact sits) may occur. This is painful and may result in blurred vision.
In order to avoid problems, contact lens wearers must be very anal about changing the lens as directed, be very clean when changing the lens, replace or switch cleaning fluid at the first sign of problems, and of course be checked by an eye doctor regularly.
Anyone with contacts who has a red, painful or itchy eye, with or without blurry vision or discharge, should be seen by a doctor. At the first sign of problems, ditch the contacts and go old school with glasses. You might be able to avoid a more serious infection this way.
Bottom line is that there is no free lunch in the universe. Contacts are great, but come with some baggage.