Wearing novelty "evil" or glow-in-the-dark contact lenses for Halloween can turn into a real horror show, optometrists warn.

The dress-up lenses can cause serious eye disorders or infections, permanent eye damage and blindness, says the Optometrists Association Australia (NSW/ACT).

Chief Executive Andrew McKinnon said people should think twice before wearing "evil or glow-in-the-dark non-prescription contact lenses as part of their Halloween costume this Saturday".

"Optometrists are seeing patients suffering from inflammations, abrasions and blinding infections caused by decorative lenses that often don't meet Australia's strict medical standards and are obtained from unauthorised suppliers."

Australian law requires that contact lenses only be supplied by qualified optometrists or other authorised professionals.

Despite this, Mr McKinnon said many over-the-counter decorative lenses were still being sold illegally at markets and other locations to unwitting purchasers.

In the US, Halloween is the time when Americans use decorative lenses the most and it is also the time when the greatest eye health problems occur.

Mr McKinnon said there were concerns this trend would be replicated here, as a rising number of young Australians were now observing the October 31 tradition.

"Australia should not follow America's lead", Mr McKinnon said when it came to the risk to eye health.