More than two-thirds of middle-aged adults are delaying their eye tests despite having problems.

A survey by YouGov commissioned by Specsavers showed that 70% of adults between 40 and 59 put off getting their sight checked by more than a month when having trouble with their vision.

Longer delays were not uncommon, with almost half waiting for more than six months to get help and one in five stalling for more than two years.

Chair of Ophthalmology NZ Dr Sonya Bennett told RNZ it was "probably human nature" to avoid confronting health problems.

"It's not uncommon for us to hear the story that they've put off getting seen until they've got quite significant issues."

People would find ways to cope before seeing an optometrist "because they actually don't want to wear glasses" out of vanity or perceived impracticality, she said.

YouGov's survey found one in five avoided wearing glasses despite needing them because of social perception.

It found half of respondents simply increased texts and display settings on their devices to cope - with a third simply missing out on certain activities because of their eyesight.

Dr Bennett explained that "presbyopia" was the most common age-related cause of eyesight loss, often setting in around middle age.

"It gradually affects your ability to read at near [distance]. Distance vision is usually in most cases okay, but you just lose the ability to see things up close.

"And that's because what we call 'accommodation' - which is the ability to focus - reduces with ageing due to changes in the lens, inside the eye and changes in the muscle that moves the lens."

The survey found nine in 10 had never heard the medical term for this common condition.

The only real danger of delaying getting help was if there were another underlying disease, such as glaucoma, where vision could not be regained once lost she said.

She recommended seeing an optometrist as the first port of call when struggling with eyesight.