Whanganui optometrist John Mellsop helps out in Fiji

The moment when a patient sees things they haven't seen for a long time is a special one for Whanganui optometrist John Mellsop.

"You put a pair of glasses on [them] and their faces light up," he said.

He had a few of those moments last week, while working in rural Fiji. He saw people with advanced cataracts who will need surgery, and people with growths caused by long-term exposure to ultraviolet light.

He gave glasses to two school boys who had been too short-sighted to do their school work, and he handed out sunglasses to people who work outdoors a lot.

Mellsop was one of four New Zealand optometrists based at Labasa, in Fiji's northern large island.

They went out each day with equipment and nurses to rural schools and health centres to examine the eyes of subsistence farming people.

The two teams saw 950 people in a week, and the conditions they saw had often gone untreated and were at "end stage".

The took glasses donated by New Zealanders, which had been cleaned up and measured, and they gave them away.

"We had all the gear with us, and could work out what they need. It's not quite as accurate as what we would do here, but for them it makes a huge difference," Mellsop said.

It's not the first time he's done voluntary eye work overseas. In other years he's spent a week or two in Nepal, Papua New Guinea, Vanuatu and Tonga.

Mellsop is one of three partners in Visique Wanganui Eyecare. It contributes to Volunteer Ophthalmic Services Overseas (VOSO), a New Zealand charitable trust.

The business releases a staff member for a week or two every year, usually to a Pacific Island country. This year it was Mellsop's turn.

"It's very good being able to help so many people who aren't able to access eye services easily, and who have a real need," he said.