With Halloween fast approaching, people are being warned not to use cosmetic or ‘fun' contact lenses as part of their costumes.

According to the Association of Optometrists Ireland (AOI), in recent years, an increasing number of people have been purchasing seasonal or fun contact lenses online or from pop-up costume shops.

However, the sale of these products is illegal and they can cause serious eye damage, including permanent vision loss, it pointed out.

The association's optometric advisor, Lynda McGivney Nolan, said that studies from around the world have clearly shown why these lenses are more likely to cause complications, such as eye infections and conjunctivitis.

"Firstly, cosmetic contact lenses are more difficult to clean and sterilise because of the materials they are made of and the pigments which colour them. This makes microbial adherence much stronger.

"The second major risk is that the lenses are not fitted by a registered practitioner, so adherence to safe insertion and removal are often not practiced, resulting in a very high level of complications," she explained.

The AOI is calling on parents and schools to warn children and young adults about the dangers of using these products and to never purchase contact lenses that are supplied through websites or costume shops.

"Not only is it dangerous, but it is illegal and evidence of shops supplying these lenses should be reported to the State health and social care regulator, CORU," Ms McGivney Nolan said.

The AOI pointed to a US study carried out last year, which found that the quality of contact lenses sold without a prescription was very poor. Microbes were found to be living on 48% of decorative lenses when they came out of the packet.

In Ireland, contact lenses are a regulated product and can only be fitted and supplied by a qualified, regulated healthcare professional, such as an optometrist.