U.S. Food and Drug Administration (FDA) issued educational materials concerning decorative contact lenses.

According to FDA, decorative contact lenses are classified as medical devices in US. Citizens should not buy contact lenses from a street vendor, a beauty supply store, flea market, novelty store or Halloween store—and prescription is always required. Wearing decorative contact lenses can be risky and cause serious damage to your eyes if the lenses are not used correctly. These risks include:

• A cut or scratch on the top layer of your eyeball (Corneal Abrasion)
• Allergic reactions like itchy, watery red eyes
• Decreased vision
• Infection
• Blindness

When wearing any type of contact lenses, be aware of signs of possible eye infection, which include:

• Redness
• Pain in the eye(s) that doesn't go away after a short period of time
• Decreased vision

If users have any of these signs, they need to see a licensed eye doctor (optometrist or ophthalmologist). An eye infection could become serious and lead to blindness if it is not treated.

In order to minimise these risks, FDA provided several recommendations. For details, please refer to FDA website:
http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/HomeHealthandConsumer/ConsumerProducts/ContactLenses/ucm270953