Costume contact lenses can literally create an eye sore called a corneal ulcer, with symptoms similar to corneal abrasions. The ulcers sometimes appear as a white dot on the iris, the colored part of the eye, and may require treatment with medicated eye drops. When the ulcers heal, they can scar over and permanently and adversely affect vision.
Both corneal abrasions and ulcers create openings in the eye, making them more vulnerable to bacteria, viruses and amoebas. All of these organisms can cause serious eye infections known as keratitis. A 2011 study found that wearing cosmetic contact lenses increased the risk of keratitis by more than 16 times. Some infections, such as herpes simplex, can be recurring and difficult to eradicate, while a number of bacteria have become resistant to common antibiotic eye drops.