NZ cataract questionnaire flawed, study finds

Friday, 29 November 2019

Cataract procedures are the most frequently performed surgical procedure in this country.

A questionnaire used to help decide who gets publicly funded cataract surgery in New Zealand is flawed and fails to identify those patients who will most benefit from the procedure, a new study has found.

The questionnaire could be replaced by a higher quality questionnaire that's been used overseas for many years, the authors suggest.

About 16,500 publicly funded cataract procedures are completed each year, making it the most frequently performed surgical procedure in this country.

Deciding who gets surgery depends on the type of cataract, the likelihood of improved vision and a 'impact on life' (IoL) questionnaire.

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'The results of this study demonstrate that the IoL does not accurately assess [the vision-related quality of life] for patients that require cataract surgery in New Zealand,' found the five co-authors led by Sunny Li and James McKelvie.

McKelvie, an eye surgeon and academic at the University of Auckland, had administered several thousand of these questionnaires and in his experience 'many people are very confused and had difficulty answering'.

The questions were 'quite abstract and some people struggled to understand what the question was asking', he said in an interview.

But there was a simple way test the questionnaire. After successful cataract surgery, ask patients to resit the questionnaire. You'd expect their vision-related quality of life to have improved.

But that wasn't always the case. 'We saw a poor correlation between poor vision and the answers.'

'In a nutshell, we found the questionnaire lacked sensitivity to accurately rank patients on who will benefit from surgery,' McKelvie said.

James McKelvie, an eye surgeon and academic at the University of Auckland, had administered several thousand of these questionnaires.

Meanwhile, the international questionnaire, called Catquest-9SF, 'provides a more accurate assessment' of vision-related quality of life, according to the study.

'It's very easy and quick to administer, and the results were reliable and predicted vision-related quality of life very well in the NZ population,' McKelvie said.

It's used internationally as a benchmarking tool.

The authors cautioned that the small sample size – 41 patients – may lessen the power of the study.

This was the first time the existing New Zealand questionnaire had been assessed, McKelvie said, and 'it takes studies like this to look critically at these things and [ask] are they performing well'.

'Now we've got this data we can move forward and either change the questionnaire to make it more sensitive … or perhaps adopt a different questionnaire.

'This is the first step in quality improvement.'

'The Ministry of Health is aware of the article and provided data to the research group for analysis,' a spokesperson said.

'We always welcome findings that can contribute to the ongoing refinement of clinical prioritisation criteria and we're considering the results of this paper.'

The existing New Zealand questionnaire was broader than Catquest and assessed 'multiple health domains', the spokesperson said.

'At end of day, we want to use our limited resources to treat those patients who will benefit the most,' McKelvie said.

He was also involved in two recent studies that looked at ACC data on 75,601 children and 332,418 adults with eye injuries over 10 years.

The Kiwis most likely to suffer eye injuries were rural men aged between 20 and 29 years.

Rural settings had almost double the rate of eye injury as urban settings, and the most common injury was 'struck by object'.

Patients were 76 per cent male.