"He was supposed to play with it very carefully. Obviously he wasn't as careful as he could have been and, hey presto, it's so easy," said Mr Drummond.
Finn, 14, is among about 6000 children aged 14 or younger each year to suffer an eye injury, according to Accident Compensation Corporation claims data.
Most - nearly 3500 cases last year - occurred in the home, followed by 1263 at schools and 523 at sport or recreation venues.
The first accident left Finn with an eye full of blood and put him in hospital for a week. The treatment was eyedrops and bed rest.
The eye recovered from the trauma but its drainage channel was damaged, putting it at increased long-term risk of glaucoma, a condition which can cause blindness if not treated in time. The second accident, although less serious, led to the same kind of damage to the drainage channel in that eye.
The Drummond family, of Forrest Hill on Auckland's North Shore, have had more than their share of medical troubles. Finn's twin sister, Breana, was born with heart defects that necessitated surgery when she was a baby.
Eye specialist Dr Justin Mora said Finn's vision was good but he must have annual checks on the pressure in his eyes because of the damage to their drainage systems and the increased risk of glaucoma.
Finn - a keen yachtsman who sails a Starling dinghy - said his accidents had not made him more cautious with his eyes.
"I'm still the same, it's just unfortunate events that happen. There's nothing that I really think about - you do what you do and if something happens, it happens."
According to ACC stats, by five-year age bands, most eye injury cases, 2386, were in those aged 4 or younger; 1978 were in children aged 5 to 9; and 1694 were in 10- to 14-year-olds.
Dr Mora, commenting on the ACC data, said many eye burn injuries were probably caused by fireworks.
"We have all sorts of things. I have seen children with vision loss from being raked in the eye by a cat's claw, through to kids being hit in the eye by a ball.
"If it's in the age group under 7 and it affects the vision, then they often end up with a combination of reduced vision from the injury and laziness in the visual development."
Treatment of lazy eye or "amblyopia" - which can involve glasses and a patch on the good eye - is best done when children are young.