After finally seeing him on November 22, following another assessment from Specsavers, the DHB eye clinic specialist wrote to Darlow's GP saying they had received a number of referrals over the past few months and "all confirmed he had reasonable vision".

This was despite the "urgent referral" from the GP and information about him not being able to use the toilet, see people or the television, given six weeks earlier.

Darlow feels Specsavers took too long to send their referrals to the DHB, and the DHB needed to act sooner.

After the Herald approached Specsavers for comment, the company launched an investigation into his claims of a delay in sending the referral - something Darlow believes contributed to him losing his sight.

"We have immediately commenced a full investigation, which includes an audit of clinical records and a review of people and processes in relation to this matter," Specsavers' director of optometry professional services, Ben Ashby told the Herald.

Until the investigation had been completed, Ashby said the company was unable to provide any further information or comment on the situation.

Bay of Plenty DHB's acting business leader in surgery, anaesthesia and radiology, Dorothy McKeown, said Darlow was seen by an ophthalmologist on November 22 last year.

"This was within the grading timeframe of four months, based on the information set out in the optometrist's referral letter," she said.

McKeown said all patients were graded from one to four clinical priority, which determined how quickly they were seen. Darlow's case was graded a four, the lowest priority, and was not upgraded despite his GP's urgent referral.

"The grading was based on the information contained in their referral letter," she said.

McKeown said results of an examination completed in early November showed no "appreciable" change since the first referral on August 31.

Patients with possible high risk glaucoma were always categorised as grade 4.

Blind Foundation chief executive Sandra Budd said Darlow's case was not an isolated one.

"We want our country to do better at taking eye care seriously, and we are focusing efforts on increasing access for New Zealanders to eye health services together with the Eye Health Coalition," Budd told the Herald.

Darlow ended up having surgery on December 14 to remove two cataracts - six months after originally being given a change in prescription for his glasses.

While the cataracts were successfully removed, eye surgeon Dr Sam Kain said - in a letter to the GP - his vision had been "significantly impaired by glaucoma and his vision now is probably as good as we can make it".

Glaucoma is an incurable disease but it can be treated to prevent further loss of vision if it is detected early enough.

Darlow now relies on the full-time care of his partner.

Darlow's medical timeline:

• June 1, 2017 - Darlow gets an eye exam at Specsavers and has a minor change in prescription.

• July 13 - Darlow sees his GP after a fall damages his glasses. GP notes sight change and suggests an optometrist review.

• August 18 - GP notes Darlow had visited Specsavers and refers him back to them.

• August 31 - DHB receives referral from Specsavers and makes an appointment in January.

• September 12 - GP receives note from DHB saying the referral has been accepted.

• September 14 - Darlow says his eyes have got worse. GP also lodges a referral with the DHB.

• October 4 - Darlow sees GP who logs an "urgent referral" with the DHB noting that he was missing the toilet pan, only seeing outlines of people and unable to watch TV.

• November 6 - DHB sends letter to GP advising Darlow go back to the optometrist.

• November 16 - Darlow sees GP again. GP calls DHB for an urgent appointment saying he was "essentially blind" and makes a referral to Specsavers.

• November 20 - Darlow sees optometrist at Specsavers who makes an urgent referral to DHB.

• November 22 - Darlow sees DHB specialist who notes no perception of light in left eye and small amount in right eye.

• November 27 - DHB specialist refers Darlow for surgery.

• December 14 - Surgery is performed.