One of the more short-term effects of leaving your lenses in for weeks/months/years at a time is a contact lens infection*. I had a number of these over the course of a few years before my optometrist switched me to another brand of lens. Acquiring one of these infections is not a fun experience, and it can ruin your eyesight.
- Wearing lenses for long periods of time - especially lenses that aren't specifically designed for this purpose.
- Placing "dirty" lenses into one's eyes.
- Improper storage or cleansing of the lenses.
- A lens that "won't remain centered in your eye." If it seems like when you blink that your lens is being pulled either too far upward or downward in your eye, it's likely an infection. This is both the first symptom to appear and the most common.
- Thick, colored mucus buildup either on the lens itself or throughout the eye. If you're careless, the mucus will start to deposit on your eyelashes. Needless to say, this is not often listed as a beauty tip.
- Persistent tearing of the eye.
- Small, raised bumps on the inner wall of the eyelid.
- Intense pain or bleeding in the eye.
* - Although this seems to imply that it's the actual lens that's infected, it's rather an infection caused by the lens. However, the slightly confusing name is also the most commonly used, and thus is what is used here.
- Most of the time, the infection will remedy itself after roughly a week of not wearing lenses. However, seek treatment. Your vision is, you know, important and such.
- If you suspect you have a contact lens infection, immediately remove the lens from your eye and schedule an appointment with a specialist.