Don't be fooled into buying those cheap tinted sunglasses from the petrol station or dairy this summer - if you wear them out in the sun, there's a chance you may do more damage to your eyes than if you don't wear them at all.
OPSM national eyecare manager Matt Whiting - an optometrist himself who is in charge of OPSM's New Zealand optometrists - said the biggest mistake people made when they bought sunglasses was thinking that all dark, tinted glasses gave UV protection.
"There's a difference between tint and UV protection," Mr Whiting said. "If you've got a tinted pair of sunglasses that don't have 100 per cent UV protection, the tint will cause your pupils to increase in size.
"So what will happen is that more UV light will go into the eyes because of the increase in tint so you'll do yourself more UV damage rather than less."
Mr Whiting says you get what you pay for.
An optometrist's opinion was important if you were serious about eye protection, he said. Otherwise, poor choice of sunglasses could cause "irreversible" eye damage.
Excessive amounts of UV light could cause cataracts, cancer of the eyes and pterygium - in which the skin on the white part of the eye grew over the coloured part.
"When that becomes really bad it has to be cut off," Mr Whiting said.
Melissa Hay, an optometrist at Visique Milford in Auckland, said it was important sunglasses had a good "wrap", as 60 per cent of harmful light damage came from the side of the eyes.
Ray Ban-style glasses were fashionable, but "not the best option" for eye protection.
However - while cheap, non-UV-protected glasses should be avoided - Ms Hay said people did not have to pay exorbitant amounts for good eye protection.
"Anywhere between $50 and $100 you're paying a good price to get a good product," she said.
"Anything above that - if you want to spend $500 on a pair of Guccis - is really purely for fashion.
"You're not necessarily getting anything better."
Buy the right sunnies
• Make sure sunglasses are 100 per cent UV protected.
• Dark tint does not protect the eyes unless it is combined with UV protection.
• The colour of the lens is irrelevant to eye protection.
• $50 to $100 should get you a pair that will protect your eyes.