Radio New Zealand - Te Reo Irirangi o Aotearoa

The Association of Optometrists warned that wearing decorative contact lenses as part of people's costumes for Hallowe'en parties on Saturday night could have tragic results.

It says lenses that can be bought over the internet, or from places such as tattoo parlours may be unhygienic, a bad fit for the eye, or made of materials that do not allow oxygen to pass through.

This can lead to eye damage, infection and even the loss of vision, the association warns.

Spokesperson Andrew Sangster says it's possible to lose an eye, with some bacteria able to destroy within 72 hours.