A contact lens is a clear piece of plastic that sits on the surface of the cornea. It corrects for your glasses prescription, so it allows you to see very well without the need for cumbersome glasses. Contact lenses, if used appropriately, are a wonderful tool to get excellent vision. In fact, depending on your glasses prescription, many times people see better with their contacts than they do with their spectacles. Unfortunately, contact lenses can be very dangerous if not used correctly. As a cornea specialist at North Shore Eye Care located on long island, I have seen many cases of contact lens related damage to the eyes.