Eye irritation symptoms, dryness, redness, and grittiness have been reported far more frequently among contact lens wearers and with greater Severity.

http://en.wikipedia.org/wiki/Human_eye

There are more and more people wearing contact lens now and dry eyes appear to be the most common complaint among contact lens wearers.Although both contact lens wearers and spectacle wearers experience similar eye irritation symptoms, dryness, redness, and grittiness have been reported far more frequently among contact lens wearers and with greater severity than among spectacle wearers.