Every year many costume stores carry contacts that are not properly made and may carry bacteria.
Read below an article from Reuters Health which goes over a study which followed 30 people with costume contacts.
(Reuters Health) - Colored contact lenses that can make brown eyes vampire red or feline yellow to perfect a Halloween costume may also make it harder to see during a night out on the town, a Korean study suggests.
Researchers did vision exams on 30 people wearing clear lenses and then repeated the tests with colored versions that left varying amounts of untinted open space around the pupil, a region known as the optical zone. - See more at: http://visianinfo.com/halloween-contacts-are-dange...
The smaller the clear optical zone got on the colored lenses, the harder it was for people to see well, the study found. Objects at a distance got a bit blurrier, and participants also lost some ability detect contrast needed to spot dark things at night or pale items against a light background. - See more at: http://visianinfo.com/halloween-contacts-are-dange...
“For the most part, if you are going to wear colored contacts for a few hours on Halloween, the likelihood of a problem is very small,” said Dr. Oliver Schein, an ophthalmology researcher at the Johns Hopkins Wilmer Eye Institute in Baltimore who wasn’t involved in the study. - See more at: http://visianinfo.com/halloween-contacts-are-dange...
The trouble comes when people buy this costume accessory without seeing an eye care professional, said Dr. Edward Manche, director of cornea and refractive surgery at Stanford Health Care in California. - See more at: http://visianinfo.com/halloween-contacts-are-dange...
“Many if not most of the people wearing the lenses obtain them over the counter, online or borrow them from friends,” Manche, who wasn’t involved in the study, said by email. “This often leads to poorly fitting lenses as well as use by people with no instruction on the care and wearing of lenses.” - See more at: http://visianinfo.com/halloween-contacts-are-dange...
In the study by Tae-im Kim of Yonsei University College of Medicine in South Korea, and colleagues, participants tried out lenses with three different clear optical zone diameters – 4, 5, and 6 millimeters. - See more at: http://visianinfo.com/halloween-contacts-are-dange...
They found just a millimeter could mean the difference between normal vision and the development of slight changes in sight. - See more at: http://visianinfo.com/halloween-contacts-are-dange...
While the study, published in the British Journal of Ophthalmology, is small and additional research is needed to more firmly establish the connection between the clear optical zone diameter and any vision problems, the researchers recommend a minimum pigment-free zone of 6 millimeters. - See more at: http://visianinfo.com/halloween-contacts-are-dange...