Visit the family's Givealittle page here.
"No one can tell us how long Denon will have vision," the couple wrote on their page. "We can't afford the vision it will cost our son if we wait. Time really is of the essence."
It's believed Denon inherited the gene that causes the disease; Mrs Andrew's two uncles were blind by their late teens.
"Unfortunately, there is no data on them at the same age as Denon. It would appear, though, that Denon is losing vision rapidly and may be more advanced than my uncles at a similar age," Mrs Andrew said.
Denon's eye surgery would be more expensive than it would be for an adult because he must be fully anaesthetised for it.
On top of that, Denon's sight is also threatened by retinitis pigmentosa, a rare, inherited disease in which the light-sensitive retina of the eye slowly degenerates until the sufferer is blind.
Though there is no cure, Denon has been referred to a genetic specialist in Auckland.
"The hope is to identify the gene causing the disease and become registered on the Genetic Registry.
"Once we are on the register, we can expect to be contacted once a cure for this gene is identified."
It's hoped a cure might be found within three years.
"Please help us to fight these terrible diseases," Mrs Andrew said. "It breaks my heart to have started a vision bucket list for our boy.
"When asked what he wanted to see, he gave us a few great starting points."
The couple said they were grateful for any donations towards their target and any extra money would go to retinitis pigmentosa research.
Last night, the fund had reached nearly $2000.
It's not the first time Denon has had a serious health complication in his short life.
In May 2011, at the age of 10 months, Denon had surgery in the Starship hospital for septic arthritis, which caused an infection that damaged his hip so badly he now has one leg shorter than the other and sometimes can't walk.
Tobin Chisnall, who featured on Givealittle last week after he was struck down with the same rare condition as his older sister Lucia, is making a recovery.
The 3-year-old was in a coma and not expected to wake up after being diagnosed with acute necrotising encephalopathy of childhood, but he is now able to talk and move around.
Though he cannot see very well yet and still needs rest and rehabilitation, his mother, Sarah Chisnall, said the family were amazed at his rapid progress.
She said the $70,000 that had been raised was a huge relief because it removed financial pressure and she and husband Jared were extremely grateful for it.
