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Cataract surgery is one of the most commonly performed surgeries worldwide, with approximately 10–20 million operations completed annually.[[1]] In New Zealand, approximately 16,500 cataract surgeries are completed in the public sector each year, making it one of the most frequently completed surgical procedures. In the New Zealand public healthcare system, prioritisation tools are used for ensuring fair and equitable distribution of finite healthcare resources. A standardised set of criteria have been developed with the aim of enabling access for those who stand to benefit the most from elective surgical procedures, both clinically and socially.[[2]] This framework focuses on maintaining both transparency and consistency when deciding which patients are prioritised for elective surgery.[[2]] The National Priority Criteria Project was focused on developing a set of standardised criteria to ensure the fair and equitable distribution of surgical resourcing.[[2]] For this purpose, the New Zealand Clinical Priority Assessment Criteria (CPAC) was developed, as a prioritisation tool for determining access to cataract surgery and other elective procedures.[[3]] The CPAC score summates various clinical, social and patient-specific factors into a single numerical score used to rank and prioritise patients for surgery. Along with measures of visual acuity and cataract morphology, the CPAC score includes patient responses to the Impact on Life (IoL) questionnaire. Regional CPAC thresholds determine eligibility for elective surgery for individual patients.

The IoL questionnaire comprises self-reported quantitative measurements of quality of life in six key domains: safety, social interactions, ability to meet responsibilities to others, personal relationships, personal care and leisure activities. The IoL was originally designed as a prioritisation tool for orthopaedic surgery. The IoL is now routinely used to assess vision-related quality of life (VRQoL) for prioritisation of cataract surgery. Despite its widespread use in New Zealand, validation of the IoL as an assessment tool for VRQoL has only recently been completed and results highlighted the IoL is poorly suited for assessment of this metric.[[4]] The IoL questionnaire was compared to the Catquest-9SF, a widely used and well validated assessment tool for measuring VRQoL.[[5,6]]

Several studies have confirmed ethnic disparity in access to cataract surgery. In the United States, African-American and Latino-American patients have a higher unmet need for cataract surgery when compared with their “White” counterparts.[[7,8]] In New Zealand, Māori are typically under-represented in the overall number of cataract surgery patients, while commonly presenting with more advanced cataracts and worse preoperative visual acuity.[[9,10]] It is important to understand how systemic factors, including surgical prioritisation, may create barriers to accessing cataract surgery for Indigenous populations in New Zealand. [[11]]

The aim of this study is to examine the relationship between patient reported IoL scores and ethnicity for patients presenting with cataracts in New Zealand. Māori have lower life expectancy and significantly higher rates of almost all chronic and infectious diseases when compared with non-Māori.[[12]] The IoL is not specific to vision, and is also used in other surgical specialities in New Zealand as a tool to assess morbidity-associated quality of life. Poor health status has a significant impact on quality of life. The working hypothesis was that Māori who are prioritised for cataract surgery would report worse quality of life scores as measured on the IoL compared with non-Māori after controlling for age, gender, visual acuity and cataract type.

Methods

The current study is a retrospective cohort study of all patients prioritised for public-funded cataract surgery between November 2014 and March 2019 in New Zealand. This study adheres to the tenants of the Declaration of Helsinki and the standards set by the National Ethics Advisory Committee.[[13]] Furthermore, this study met the exemption criteria after formal review as outlined by the New Zealand Health and Disability Ethics Committee.[[14]]

The New Zealand Ministry of Health National Prioritisation Web Service (NPWS) database was used to obtain national prioritisation data for cataract surgery spanning the duration of the study. Data included best-corrected visual acuity in the operative eye, best-corrected binocular vision, cataract morphology grading, predicted postoperative visual outcome and IoL questionnaire responses. The IoL prioritisation tool consists of six questions asking the patient to score quality of life in six domains including social interactions, personal relationships, ability to fulfil responsibilities to others, personal care, personal safety and leisure activities. All six questions are scored on a scale of 1 (no difficulty) to 6 (extreme difficulty). A total IoL composite score is then calculated by summing the scores from all six questions. Patient demographic and ethnicity data was obtained from the National Health Index (NHI) database and joined to the NPWS data using the NHI as a primary key. Each patient was associated with a single ethnicity from the data provided by the NZ Ministry of Health. Joined data included date of birth, gender, ethnicity, and district health board of domicile. Patients who had had two or more prioritisation events on the same day, with differing clinical answers (a same-day re-prioritisation event), were excluded from the main analysis. The number of re-prioritisation events and ethnicity were investigated in a separate sub analysis. All data was de-identified prior to analysis.

Statistical analysis

Visual acuity was converted to logMAR units for statistical analysis. All statistical analysis was completed using R statistical software (R Foundation for Statistical Computing, Vienna, Austria). To evaluate the significance of ethnicity for patient scores recorded on the IoL, discriminant analysis and logistic regression were used to see if attributes (IoL score, age, logMAR acuity in one or both eyes) could be used to predict ethnicity. Various attributes were used in the models to determine whether discrimination could be improved. Models were also fitted where patients who did not identify as Māori were grouped into a single non-Māori category to comprehensively evaluate any significant differences in IoL score that may exist between Māori and non-Māori. Various hierarchical and non-hierarchical cluster analysis techniques were used on the data to see if the patients could be grouped such that patients within the same group were similar to each other. The identified cluster groups were then compared to the ethnic groups, using the measured patient attributes. The expectation-maximisation (EM) algorithm[[15]] was used to fit a finite mixture model to the data and determine the groups to be fitted in the model.

Results

There were 58,648 prioritisation events for cataract surgery spanning four and a half years between November 2014 and March 2019 in the New Zealand public healthcare system. Of these prioritisation events, all had documented CPAC scores but 12,296 did not have the IoL questionnaire component of the score specified and were excluded from analysis. The remaining 46,352 prioritisation events with IoL scores available were included for analysis.

The study population had a mean age of 74.4 years, and had a slight female preponderance (57%). The absolute number and relative proportion of each ethnic group is summarised in Table 1. The average BCVA of the operative eye was 0.73 logMAR (6/32 Snellen equivalent) while the average binocular BCVA was 0.31 logMAR (6/12 Snellen equivalent). The overall mean IoL score was 22.5 (SD 7.8) and the average CPAC score was 59.4 (SD 13.6). The average age, mean IoL score and CPAC scores are summarised by reported ethnicity in Table 1. Māori and Pacific people presented for cataract prioritisation at a younger age (68.5 years and 66.7 years, respectively) compared with all other ethnic groups. There was only a marginal difference when comparing the mean IoL scores of Māori 22.8 (95% CI 22.6, 23.1) and non-Māori 22.4 (95% CI 22.4, 22.5). There was a mean IoL score of 22.9 (SD 7.8) for patients’ first operative eye and 22.3 (SD 7.7) for second operative eye, again with no statistically significant difference between the two groups.

Discriminant analysis and logistic regression demonstrated that for each of the classifiers fitted, 66% to 69% of the observations were correctly classified. Table 3 shows that the majority of individuals with Māori ethnicity were classified with another ethnic group. Models were also fitted where the patients had been reclassified as either Māori or non-Māori. For each of the classifiers, 87 to 90% of the observations were correctly classified. However, it can be seen from Table 4 that the majority of the patients with Māori ethnicity were classified with the non-Māori ethnic group.

Analysis of the groupings identified using cluster analysis demonstrated no relationship between the cluster analysis groups and different ethnicities. The data was also investigated to determine whether subsets of various attributes were more predictive of the ethnicity groups. Mixture model analysis identified six groups when fitting models to each of IoL score and best corrected logMAR binocular vision separately (Table 5), and three groups when using all of the attributes (Table 6). These groups did not correspond to ethnicity. Discriminant analysis was also unable to separate the individuals into the ethnic groups. Models were then fitted with five groups specified. It can be seen in Table 7 and Table 8 that the identified groups also did not correspond to ethnicities. The ethnicities were combined such that the groupings were Māori versus the others. Cluster analysis found three groups in the data for Māori versus the Others. These groups did not correspond to ethnicity. In summary, no statistically significant differences in IoL scores between the ethnic groups including Māori and non-Māori were identified.

Views Tables 1–8.

Visual acuity

Pacific people and Māori were noted to have significantly (p<0.001) worse best corrected visual acuity (95% CI 0.915–0.940 vs 0.688–0.698 for other ethnicities) in the operative eye at prioritisation, when compared with other ethnic groups as outlined in Table 2. Best corrected binocular vision was not significantly different (p=0.834) between ethnic groups (95% CI 0.306–0.319 for Māori and Pacific people vs 0.310–0.316 for other ethnicities).

Discussion

The IoL score comprises 13% of the total CPAC score used to prioritise public-funded cataract surgery in New Zealand. The ability of the IoL to discriminate between eligible patients, and prioritise those who have the greatest need and are most likely to benefit from cataract surgery, is critical to ensure fair and equitable distribution of limited healthcare resources.

There are well established disparities in health status, access to treatment and health outcomes for Māori and Pacific people in New Zealand. The Health and Disability System Review released in June 2020 highlighted the significantly worse health outcomes for Māori, and proposed various strategies to address these disparities.[[16]]

Results of the current study noted that VRQoL, as assessed using the IoL, were very similar for Māori and non-Māori patients presenting with cataract. These results are surprising, as it is well established that Māori have significantly higher rates of non-communicable disease and a higher burden of all-cause morbidity when compared with non-Māori.[[17]] As poor health is closely associated with quality of life, it would be reasonable to expect that Māori responses to the IoL, which is not specific to vision, should reflect the greater morbidity associated with this group. The analysis of the IoL questionnaire responses in the current study suggest that Māori have similar quality of life to non-Māori as reported by the IoL, despite high rates of morbidity in the cataract age group and a sufficiently large population included in the study. This finding is at odds with a large number of studies that have identified significant inequalities for Māori.[[17]] It seems unlikely that Māori and Pacific people enjoy similar quality of life to patients of other ethnicities despite well-established disparities in health status. Visual impairment is closely linked to decreased quality of life, and patients who undergo cataract surgery typically report significant improvements in quality of life following surgery.[[18]] The more likely explanation for the results of the current study is that the IoL is poorly suited to accurately measure quality of life in Māori and/or non-Māori.

A recent study looking at validation of the IoL questionnaire identified major issues with its ability to assess VRQoL in cataract patients.[[4]] The Catquest-9SF, an alternative tool for measuring VRQoL, has been extensively validated for use in assessing VRQoL in New Zealand and elsewhere, and does not have the same accuracy and reliability issues that have been identified with the IoL assessment tool.[[4]] The current study contributes to this growing body of evidence that the IoL questionnaire may be an inappropriate tool for prioritisation of patients for cataract surgery in New Zealand, and in particular, may disproportionally disadvantage Māori and Pacific people who require cataract surgery.

The current study highlights the need for rigorous validation of clinical assessment tools used as a basis for allocation of public-funded healthcare resources. There is a very real risk that poorly validated tools may contribute to widening health inequalities and present barriers to accessing treatment for ethnic minorities.

Summary

Abstract

Aim

The ‘Impact on Life’ (IoL) questionnaire is a patient reported quality-of-life assessment tool used to prioritise cataract surgery in New Zealand (NZ). This study evaluated the association between ethnicity and IoL questionnaire responses.

Method

This is a retrospective cohort study of patients prioritised for public-funded cataract surgery between November 2014 and March 2019 in New Zealand. Data were extracted from the New Zealand Ministry of Health National Prioritisation Web Service database. Ethnic, demographic and IoL data for all patients who were prioritised for surgery were analysed after controlling for age, gender, visual acuity and cataract type.

Results

Of the 58,648 prioritisation events, over the four-and-a-half-year period, 46,352 prioritisation events had documented scores for the IoL questionnaire. The study population had a mean age of 74.4 years and had a female preponderance (74%). The average IoL score was 22.5/36 (SD 7.8). After controlling for age, gender, visual acuity (VA) and cataract type, there was only a marginal difference between Māori and non-Māori IoL scores (22.8/36 vs 22.4/36) despite statistical significance for the difference (p=0.001). Māori and Pacific people presented at a younger age (68.5 years and 66.7 years, respectively) with worse visual acuity than other ethnic groups (mean range 70.1–76.7 years). Mean IoL scores were 23.0/36 for Māori and Pacific people and 22.4/36 for other ethnic groups.

Conclusion

Māori and Pacific people present younger with worse VA and more advanced cataracts at time of surgical prioritisation when compared with other ethnic groups. Despite these differences, after controlling for confounding factors, the mean IoL score did not differ to a level that was clinically significant between different ethnic groups in New Zealand at time of prioritisation for cataract surgery. These results suggest that there are no meaningful ethnic specific differences in patient reported quality of life for patients with cataract in New Zealand after controlling for other factors. Alternatively, the IoL tool may lack the sensitivity to detect meaningful ethnic disparities that may exist for quality of life in this cohort of patients.

Author Information

Nancy Wang: Department of Ophthalmology, University of Auckland, New Zealand. Lyn Hunt: Department of Statistics, University of Waikato, New Zealand. James McKelvie: Department of Ophthalmology, University of Auckland, New Zealand; Department of Ophthalmology, Waikato District Health Board, New Zealand.

Acknowledgements

Correspondence

James McKelvie: Department of Ophthalmology, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. +649 3737 999, fax +649 367 7173.

Correspondence Email

james@mckelvie.co.nz

Competing Interests

Nil.

1) Vision 2020: the cataract challenge. Community Eye Health. 2000;13(34):17-9.

2) Hadorn DC, Holmes AC. The New Zealand priority criteria project. Part 1: Overview. BMJ. 1997 Jan 11;314(7074):131-4.

3) Derrett S, Devlin N, Hansen P, Herbison P. Prioritizing patients for elective surgery: a prospective study of clinical priority assessment criteria in New Zealand. Int J Technol Assess Health Care. 2003 Winter;19(1):91-105.

4) Li SS, Misra S, Wallace H, Hunt L, McKelvie J. Patient-reported quality of life for cataract surgery: prospective validation of the “Impact on Life” and Catquest-9SF questionnaires in New Zealand. N Z Med J. 2019 Oct 4;132(1503):34-45.

5) Nielsen E, Lundström M, Pesudovs K, Hjortdal J. Validation of Catquest-9SF in Danish: developing a revised form of the Catquest-9SF - the Danish Catquest-7SF. Acta Ophthalmol. 2019 Mar;97(2):173-7.

6) Lundstrom M, Behndig A, Kugelberg M, Montan P, Stenevi U, Pesudovs K. The outcome of cataract surgery measured with the Catquest-9SF. Acta Ophthalmol. 2011 Dec;89(8):718-23.

7) Richter GM, Chung J, Azen SP, Varma R, Los Angeles Latino Eye Study Group. Prevalence of visually significant cataract and factors associated with unmet need for cataract surgery: Los Angeles Latino Eye Study. Ophthalmology. 2009 Dec;116(12):2327-35.

8) Shahbazi S, Studnicki J, Warner-Hillard CW. A Cross-Sectional Retrospective Analysis of the Racial and Geographic Variations in Cataract Surgery. PLoS One. 2015 Nov 5;10(11):e0142459.

9) Yoon JJ, Misra SL, McGhee CN, Patel DV. Demographics and ocular biometric characteristics of patients undergoing cataract surgery in Auckland, New Zealand. Clin Experiment Ophthalmol. 2016 Mar;44(2):106-13.

10) Newlands SJ, Hoy BM, Wilson GA. Cataract surgery in Hauora Tairāwhiti and need for improving access for Māori. Clin Experiment Ophthalmol. 2019 Jan;47(1):145-7.

11) Freundlich SEN, McGhee CNJ. Should we be doing more to identify barriers to cataract surgery for Indigenous populations in New Zealand? Clin Experiment Ophthalmol [Internet]. 2020 Jun 21; Available from: http://dx.doi.org/10.1111/ceo.13813.

12) Disney G, Teng A, Atkinson J, Wilson N, Blakely T. Changing ethnic inequalities in mortality in New Zealand over 30 years: linked cohort studies with 68.9 million person-years of follow-up. Popul Health Metr. 2017 Apr 26;15(1):15.

13) New Zealand Ministry of Health. National Ethics Advisory Committee. Ethical Guidelines for Observational Studies: Observational research, audits and related activities. National Ethics Advisory Committee; 2012.

14) New Zealand Ministry of Health. Standard Operating Procedures for Health and Disability Ethics Committees. Wellington (NZ): MOH;2-19 Dec.  

15) Dempster, A.P., Laird, N.M., Rubin, D.B. Maximum Likelihood from incomplete data via the EM algorithm. Journal of the Royal Statistical Society. 1977;39(1):1-38.

16) Health and Disability System Review: Final report – Executive overview. Available from: https://systemreview.health.govt.nz/assets/Uploads/hdsr/health-disability-system-review-final-report-executive-overview.pdf

17) A window on the quality of Aotearoa New Zealand’s health care 2019 | He matapihi ki te kounga o ngā manaakitanga ā-hauora o Aotearoa 2019. Available from: https://www.hqsc.govt.nz/assets/Health-Quality-Evaluation/PR/Window_2019_web_final.pdf

18) Heemraz BS, Lee CN, Hysi PG, Jones CA, Hammond CJ, Mahroo OA. Changes in quality of life shortly after routine cataract surgery. Can J Ophthalmol. 2016 Aug;51(4):282-7.

For the PDF of this article,
contact nzmj@nzma.org.nz

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Cataract surgery is one of the most commonly performed surgeries worldwide, with approximately 10–20 million operations completed annually.[[1]] In New Zealand, approximately 16,500 cataract surgeries are completed in the public sector each year, making it one of the most frequently completed surgical procedures. In the New Zealand public healthcare system, prioritisation tools are used for ensuring fair and equitable distribution of finite healthcare resources. A standardised set of criteria have been developed with the aim of enabling access for those who stand to benefit the most from elective surgical procedures, both clinically and socially.[[2]] This framework focuses on maintaining both transparency and consistency when deciding which patients are prioritised for elective surgery.[[2]] The National Priority Criteria Project was focused on developing a set of standardised criteria to ensure the fair and equitable distribution of surgical resourcing.[[2]] For this purpose, the New Zealand Clinical Priority Assessment Criteria (CPAC) was developed, as a prioritisation tool for determining access to cataract surgery and other elective procedures.[[3]] The CPAC score summates various clinical, social and patient-specific factors into a single numerical score used to rank and prioritise patients for surgery. Along with measures of visual acuity and cataract morphology, the CPAC score includes patient responses to the Impact on Life (IoL) questionnaire. Regional CPAC thresholds determine eligibility for elective surgery for individual patients.

The IoL questionnaire comprises self-reported quantitative measurements of quality of life in six key domains: safety, social interactions, ability to meet responsibilities to others, personal relationships, personal care and leisure activities. The IoL was originally designed as a prioritisation tool for orthopaedic surgery. The IoL is now routinely used to assess vision-related quality of life (VRQoL) for prioritisation of cataract surgery. Despite its widespread use in New Zealand, validation of the IoL as an assessment tool for VRQoL has only recently been completed and results highlighted the IoL is poorly suited for assessment of this metric.[[4]] The IoL questionnaire was compared to the Catquest-9SF, a widely used and well validated assessment tool for measuring VRQoL.[[5,6]]

Several studies have confirmed ethnic disparity in access to cataract surgery. In the United States, African-American and Latino-American patients have a higher unmet need for cataract surgery when compared with their “White” counterparts.[[7,8]] In New Zealand, Māori are typically under-represented in the overall number of cataract surgery patients, while commonly presenting with more advanced cataracts and worse preoperative visual acuity.[[9,10]] It is important to understand how systemic factors, including surgical prioritisation, may create barriers to accessing cataract surgery for Indigenous populations in New Zealand. [[11]]

The aim of this study is to examine the relationship between patient reported IoL scores and ethnicity for patients presenting with cataracts in New Zealand. Māori have lower life expectancy and significantly higher rates of almost all chronic and infectious diseases when compared with non-Māori.[[12]] The IoL is not specific to vision, and is also used in other surgical specialities in New Zealand as a tool to assess morbidity-associated quality of life. Poor health status has a significant impact on quality of life. The working hypothesis was that Māori who are prioritised for cataract surgery would report worse quality of life scores as measured on the IoL compared with non-Māori after controlling for age, gender, visual acuity and cataract type.

Methods

The current study is a retrospective cohort study of all patients prioritised for public-funded cataract surgery between November 2014 and March 2019 in New Zealand. This study adheres to the tenants of the Declaration of Helsinki and the standards set by the National Ethics Advisory Committee.[[13]] Furthermore, this study met the exemption criteria after formal review as outlined by the New Zealand Health and Disability Ethics Committee.[[14]]

The New Zealand Ministry of Health National Prioritisation Web Service (NPWS) database was used to obtain national prioritisation data for cataract surgery spanning the duration of the study. Data included best-corrected visual acuity in the operative eye, best-corrected binocular vision, cataract morphology grading, predicted postoperative visual outcome and IoL questionnaire responses. The IoL prioritisation tool consists of six questions asking the patient to score quality of life in six domains including social interactions, personal relationships, ability to fulfil responsibilities to others, personal care, personal safety and leisure activities. All six questions are scored on a scale of 1 (no difficulty) to 6 (extreme difficulty). A total IoL composite score is then calculated by summing the scores from all six questions. Patient demographic and ethnicity data was obtained from the National Health Index (NHI) database and joined to the NPWS data using the NHI as a primary key. Each patient was associated with a single ethnicity from the data provided by the NZ Ministry of Health. Joined data included date of birth, gender, ethnicity, and district health board of domicile. Patients who had had two or more prioritisation events on the same day, with differing clinical answers (a same-day re-prioritisation event), were excluded from the main analysis. The number of re-prioritisation events and ethnicity were investigated in a separate sub analysis. All data was de-identified prior to analysis.

Statistical analysis

Visual acuity was converted to logMAR units for statistical analysis. All statistical analysis was completed using R statistical software (R Foundation for Statistical Computing, Vienna, Austria). To evaluate the significance of ethnicity for patient scores recorded on the IoL, discriminant analysis and logistic regression were used to see if attributes (IoL score, age, logMAR acuity in one or both eyes) could be used to predict ethnicity. Various attributes were used in the models to determine whether discrimination could be improved. Models were also fitted where patients who did not identify as Māori were grouped into a single non-Māori category to comprehensively evaluate any significant differences in IoL score that may exist between Māori and non-Māori. Various hierarchical and non-hierarchical cluster analysis techniques were used on the data to see if the patients could be grouped such that patients within the same group were similar to each other. The identified cluster groups were then compared to the ethnic groups, using the measured patient attributes. The expectation-maximisation (EM) algorithm[[15]] was used to fit a finite mixture model to the data and determine the groups to be fitted in the model.

Results

There were 58,648 prioritisation events for cataract surgery spanning four and a half years between November 2014 and March 2019 in the New Zealand public healthcare system. Of these prioritisation events, all had documented CPAC scores but 12,296 did not have the IoL questionnaire component of the score specified and were excluded from analysis. The remaining 46,352 prioritisation events with IoL scores available were included for analysis.

The study population had a mean age of 74.4 years, and had a slight female preponderance (57%). The absolute number and relative proportion of each ethnic group is summarised in Table 1. The average BCVA of the operative eye was 0.73 logMAR (6/32 Snellen equivalent) while the average binocular BCVA was 0.31 logMAR (6/12 Snellen equivalent). The overall mean IoL score was 22.5 (SD 7.8) and the average CPAC score was 59.4 (SD 13.6). The average age, mean IoL score and CPAC scores are summarised by reported ethnicity in Table 1. Māori and Pacific people presented for cataract prioritisation at a younger age (68.5 years and 66.7 years, respectively) compared with all other ethnic groups. There was only a marginal difference when comparing the mean IoL scores of Māori 22.8 (95% CI 22.6, 23.1) and non-Māori 22.4 (95% CI 22.4, 22.5). There was a mean IoL score of 22.9 (SD 7.8) for patients’ first operative eye and 22.3 (SD 7.7) for second operative eye, again with no statistically significant difference between the two groups.

Discriminant analysis and logistic regression demonstrated that for each of the classifiers fitted, 66% to 69% of the observations were correctly classified. Table 3 shows that the majority of individuals with Māori ethnicity were classified with another ethnic group. Models were also fitted where the patients had been reclassified as either Māori or non-Māori. For each of the classifiers, 87 to 90% of the observations were correctly classified. However, it can be seen from Table 4 that the majority of the patients with Māori ethnicity were classified with the non-Māori ethnic group.

Analysis of the groupings identified using cluster analysis demonstrated no relationship between the cluster analysis groups and different ethnicities. The data was also investigated to determine whether subsets of various attributes were more predictive of the ethnicity groups. Mixture model analysis identified six groups when fitting models to each of IoL score and best corrected logMAR binocular vision separately (Table 5), and three groups when using all of the attributes (Table 6). These groups did not correspond to ethnicity. Discriminant analysis was also unable to separate the individuals into the ethnic groups. Models were then fitted with five groups specified. It can be seen in Table 7 and Table 8 that the identified groups also did not correspond to ethnicities. The ethnicities were combined such that the groupings were Māori versus the others. Cluster analysis found three groups in the data for Māori versus the Others. These groups did not correspond to ethnicity. In summary, no statistically significant differences in IoL scores between the ethnic groups including Māori and non-Māori were identified.

Views Tables 1–8.

Visual acuity

Pacific people and Māori were noted to have significantly (p<0.001) worse best corrected visual acuity (95% CI 0.915–0.940 vs 0.688–0.698 for other ethnicities) in the operative eye at prioritisation, when compared with other ethnic groups as outlined in Table 2. Best corrected binocular vision was not significantly different (p=0.834) between ethnic groups (95% CI 0.306–0.319 for Māori and Pacific people vs 0.310–0.316 for other ethnicities).

Discussion

The IoL score comprises 13% of the total CPAC score used to prioritise public-funded cataract surgery in New Zealand. The ability of the IoL to discriminate between eligible patients, and prioritise those who have the greatest need and are most likely to benefit from cataract surgery, is critical to ensure fair and equitable distribution of limited healthcare resources.

There are well established disparities in health status, access to treatment and health outcomes for Māori and Pacific people in New Zealand. The Health and Disability System Review released in June 2020 highlighted the significantly worse health outcomes for Māori, and proposed various strategies to address these disparities.[[16]]

Results of the current study noted that VRQoL, as assessed using the IoL, were very similar for Māori and non-Māori patients presenting with cataract. These results are surprising, as it is well established that Māori have significantly higher rates of non-communicable disease and a higher burden of all-cause morbidity when compared with non-Māori.[[17]] As poor health is closely associated with quality of life, it would be reasonable to expect that Māori responses to the IoL, which is not specific to vision, should reflect the greater morbidity associated with this group. The analysis of the IoL questionnaire responses in the current study suggest that Māori have similar quality of life to non-Māori as reported by the IoL, despite high rates of morbidity in the cataract age group and a sufficiently large population included in the study. This finding is at odds with a large number of studies that have identified significant inequalities for Māori.[[17]] It seems unlikely that Māori and Pacific people enjoy similar quality of life to patients of other ethnicities despite well-established disparities in health status. Visual impairment is closely linked to decreased quality of life, and patients who undergo cataract surgery typically report significant improvements in quality of life following surgery.[[18]] The more likely explanation for the results of the current study is that the IoL is poorly suited to accurately measure quality of life in Māori and/or non-Māori.

A recent study looking at validation of the IoL questionnaire identified major issues with its ability to assess VRQoL in cataract patients.[[4]] The Catquest-9SF, an alternative tool for measuring VRQoL, has been extensively validated for use in assessing VRQoL in New Zealand and elsewhere, and does not have the same accuracy and reliability issues that have been identified with the IoL assessment tool.[[4]] The current study contributes to this growing body of evidence that the IoL questionnaire may be an inappropriate tool for prioritisation of patients for cataract surgery in New Zealand, and in particular, may disproportionally disadvantage Māori and Pacific people who require cataract surgery.

The current study highlights the need for rigorous validation of clinical assessment tools used as a basis for allocation of public-funded healthcare resources. There is a very real risk that poorly validated tools may contribute to widening health inequalities and present barriers to accessing treatment for ethnic minorities.

Summary

Abstract

Aim

The ‘Impact on Life’ (IoL) questionnaire is a patient reported quality-of-life assessment tool used to prioritise cataract surgery in New Zealand (NZ). This study evaluated the association between ethnicity and IoL questionnaire responses.

Method

This is a retrospective cohort study of patients prioritised for public-funded cataract surgery between November 2014 and March 2019 in New Zealand. Data were extracted from the New Zealand Ministry of Health National Prioritisation Web Service database. Ethnic, demographic and IoL data for all patients who were prioritised for surgery were analysed after controlling for age, gender, visual acuity and cataract type.

Results

Of the 58,648 prioritisation events, over the four-and-a-half-year period, 46,352 prioritisation events had documented scores for the IoL questionnaire. The study population had a mean age of 74.4 years and had a female preponderance (74%). The average IoL score was 22.5/36 (SD 7.8). After controlling for age, gender, visual acuity (VA) and cataract type, there was only a marginal difference between Māori and non-Māori IoL scores (22.8/36 vs 22.4/36) despite statistical significance for the difference (p=0.001). Māori and Pacific people presented at a younger age (68.5 years and 66.7 years, respectively) with worse visual acuity than other ethnic groups (mean range 70.1–76.7 years). Mean IoL scores were 23.0/36 for Māori and Pacific people and 22.4/36 for other ethnic groups.

Conclusion

Māori and Pacific people present younger with worse VA and more advanced cataracts at time of surgical prioritisation when compared with other ethnic groups. Despite these differences, after controlling for confounding factors, the mean IoL score did not differ to a level that was clinically significant between different ethnic groups in New Zealand at time of prioritisation for cataract surgery. These results suggest that there are no meaningful ethnic specific differences in patient reported quality of life for patients with cataract in New Zealand after controlling for other factors. Alternatively, the IoL tool may lack the sensitivity to detect meaningful ethnic disparities that may exist for quality of life in this cohort of patients.

Author Information

Nancy Wang: Department of Ophthalmology, University of Auckland, New Zealand. Lyn Hunt: Department of Statistics, University of Waikato, New Zealand. James McKelvie: Department of Ophthalmology, University of Auckland, New Zealand; Department of Ophthalmology, Waikato District Health Board, New Zealand.

Acknowledgements

Correspondence

James McKelvie: Department of Ophthalmology, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. +649 3737 999, fax +649 367 7173.

Correspondence Email

james@mckelvie.co.nz

Competing Interests

Nil.

1) Vision 2020: the cataract challenge. Community Eye Health. 2000;13(34):17-9.

2) Hadorn DC, Holmes AC. The New Zealand priority criteria project. Part 1: Overview. BMJ. 1997 Jan 11;314(7074):131-4.

3) Derrett S, Devlin N, Hansen P, Herbison P. Prioritizing patients for elective surgery: a prospective study of clinical priority assessment criteria in New Zealand. Int J Technol Assess Health Care. 2003 Winter;19(1):91-105.

4) Li SS, Misra S, Wallace H, Hunt L, McKelvie J. Patient-reported quality of life for cataract surgery: prospective validation of the “Impact on Life” and Catquest-9SF questionnaires in New Zealand. N Z Med J. 2019 Oct 4;132(1503):34-45.

5) Nielsen E, Lundström M, Pesudovs K, Hjortdal J. Validation of Catquest-9SF in Danish: developing a revised form of the Catquest-9SF - the Danish Catquest-7SF. Acta Ophthalmol. 2019 Mar;97(2):173-7.

6) Lundstrom M, Behndig A, Kugelberg M, Montan P, Stenevi U, Pesudovs K. The outcome of cataract surgery measured with the Catquest-9SF. Acta Ophthalmol. 2011 Dec;89(8):718-23.

7) Richter GM, Chung J, Azen SP, Varma R, Los Angeles Latino Eye Study Group. Prevalence of visually significant cataract and factors associated with unmet need for cataract surgery: Los Angeles Latino Eye Study. Ophthalmology. 2009 Dec;116(12):2327-35.

8) Shahbazi S, Studnicki J, Warner-Hillard CW. A Cross-Sectional Retrospective Analysis of the Racial and Geographic Variations in Cataract Surgery. PLoS One. 2015 Nov 5;10(11):e0142459.

9) Yoon JJ, Misra SL, McGhee CN, Patel DV. Demographics and ocular biometric characteristics of patients undergoing cataract surgery in Auckland, New Zealand. Clin Experiment Ophthalmol. 2016 Mar;44(2):106-13.

10) Newlands SJ, Hoy BM, Wilson GA. Cataract surgery in Hauora Tairāwhiti and need for improving access for Māori. Clin Experiment Ophthalmol. 2019 Jan;47(1):145-7.

11) Freundlich SEN, McGhee CNJ. Should we be doing more to identify barriers to cataract surgery for Indigenous populations in New Zealand? Clin Experiment Ophthalmol [Internet]. 2020 Jun 21; Available from: http://dx.doi.org/10.1111/ceo.13813.

12) Disney G, Teng A, Atkinson J, Wilson N, Blakely T. Changing ethnic inequalities in mortality in New Zealand over 30 years: linked cohort studies with 68.9 million person-years of follow-up. Popul Health Metr. 2017 Apr 26;15(1):15.

13) New Zealand Ministry of Health. National Ethics Advisory Committee. Ethical Guidelines for Observational Studies: Observational research, audits and related activities. National Ethics Advisory Committee; 2012.

14) New Zealand Ministry of Health. Standard Operating Procedures for Health and Disability Ethics Committees. Wellington (NZ): MOH;2-19 Dec.  

15) Dempster, A.P., Laird, N.M., Rubin, D.B. Maximum Likelihood from incomplete data via the EM algorithm. Journal of the Royal Statistical Society. 1977;39(1):1-38.

16) Health and Disability System Review: Final report – Executive overview. Available from: https://systemreview.health.govt.nz/assets/Uploads/hdsr/health-disability-system-review-final-report-executive-overview.pdf

17) A window on the quality of Aotearoa New Zealand’s health care 2019 | He matapihi ki te kounga o ngā manaakitanga ā-hauora o Aotearoa 2019. Available from: https://www.hqsc.govt.nz/assets/Health-Quality-Evaluation/PR/Window_2019_web_final.pdf

18) Heemraz BS, Lee CN, Hysi PG, Jones CA, Hammond CJ, Mahroo OA. Changes in quality of life shortly after routine cataract surgery. Can J Ophthalmol. 2016 Aug;51(4):282-7.

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contact nzmj@nzma.org.nz

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Cataract surgery is one of the most commonly performed surgeries worldwide, with approximately 10–20 million operations completed annually.[[1]] In New Zealand, approximately 16,500 cataract surgeries are completed in the public sector each year, making it one of the most frequently completed surgical procedures. In the New Zealand public healthcare system, prioritisation tools are used for ensuring fair and equitable distribution of finite healthcare resources. A standardised set of criteria have been developed with the aim of enabling access for those who stand to benefit the most from elective surgical procedures, both clinically and socially.[[2]] This framework focuses on maintaining both transparency and consistency when deciding which patients are prioritised for elective surgery.[[2]] The National Priority Criteria Project was focused on developing a set of standardised criteria to ensure the fair and equitable distribution of surgical resourcing.[[2]] For this purpose, the New Zealand Clinical Priority Assessment Criteria (CPAC) was developed, as a prioritisation tool for determining access to cataract surgery and other elective procedures.[[3]] The CPAC score summates various clinical, social and patient-specific factors into a single numerical score used to rank and prioritise patients for surgery. Along with measures of visual acuity and cataract morphology, the CPAC score includes patient responses to the Impact on Life (IoL) questionnaire. Regional CPAC thresholds determine eligibility for elective surgery for individual patients.

The IoL questionnaire comprises self-reported quantitative measurements of quality of life in six key domains: safety, social interactions, ability to meet responsibilities to others, personal relationships, personal care and leisure activities. The IoL was originally designed as a prioritisation tool for orthopaedic surgery. The IoL is now routinely used to assess vision-related quality of life (VRQoL) for prioritisation of cataract surgery. Despite its widespread use in New Zealand, validation of the IoL as an assessment tool for VRQoL has only recently been completed and results highlighted the IoL is poorly suited for assessment of this metric.[[4]] The IoL questionnaire was compared to the Catquest-9SF, a widely used and well validated assessment tool for measuring VRQoL.[[5,6]]

Several studies have confirmed ethnic disparity in access to cataract surgery. In the United States, African-American and Latino-American patients have a higher unmet need for cataract surgery when compared with their “White” counterparts.[[7,8]] In New Zealand, Māori are typically under-represented in the overall number of cataract surgery patients, while commonly presenting with more advanced cataracts and worse preoperative visual acuity.[[9,10]] It is important to understand how systemic factors, including surgical prioritisation, may create barriers to accessing cataract surgery for Indigenous populations in New Zealand. [[11]]

The aim of this study is to examine the relationship between patient reported IoL scores and ethnicity for patients presenting with cataracts in New Zealand. Māori have lower life expectancy and significantly higher rates of almost all chronic and infectious diseases when compared with non-Māori.[[12]] The IoL is not specific to vision, and is also used in other surgical specialities in New Zealand as a tool to assess morbidity-associated quality of life. Poor health status has a significant impact on quality of life. The working hypothesis was that Māori who are prioritised for cataract surgery would report worse quality of life scores as measured on the IoL compared with non-Māori after controlling for age, gender, visual acuity and cataract type.

Methods

The current study is a retrospective cohort study of all patients prioritised for public-funded cataract surgery between November 2014 and March 2019 in New Zealand. This study adheres to the tenants of the Declaration of Helsinki and the standards set by the National Ethics Advisory Committee.[[13]] Furthermore, this study met the exemption criteria after formal review as outlined by the New Zealand Health and Disability Ethics Committee.[[14]]

The New Zealand Ministry of Health National Prioritisation Web Service (NPWS) database was used to obtain national prioritisation data for cataract surgery spanning the duration of the study. Data included best-corrected visual acuity in the operative eye, best-corrected binocular vision, cataract morphology grading, predicted postoperative visual outcome and IoL questionnaire responses. The IoL prioritisation tool consists of six questions asking the patient to score quality of life in six domains including social interactions, personal relationships, ability to fulfil responsibilities to others, personal care, personal safety and leisure activities. All six questions are scored on a scale of 1 (no difficulty) to 6 (extreme difficulty). A total IoL composite score is then calculated by summing the scores from all six questions. Patient demographic and ethnicity data was obtained from the National Health Index (NHI) database and joined to the NPWS data using the NHI as a primary key. Each patient was associated with a single ethnicity from the data provided by the NZ Ministry of Health. Joined data included date of birth, gender, ethnicity, and district health board of domicile. Patients who had had two or more prioritisation events on the same day, with differing clinical answers (a same-day re-prioritisation event), were excluded from the main analysis. The number of re-prioritisation events and ethnicity were investigated in a separate sub analysis. All data was de-identified prior to analysis.

Statistical analysis

Visual acuity was converted to logMAR units for statistical analysis. All statistical analysis was completed using R statistical software (R Foundation for Statistical Computing, Vienna, Austria). To evaluate the significance of ethnicity for patient scores recorded on the IoL, discriminant analysis and logistic regression were used to see if attributes (IoL score, age, logMAR acuity in one or both eyes) could be used to predict ethnicity. Various attributes were used in the models to determine whether discrimination could be improved. Models were also fitted where patients who did not identify as Māori were grouped into a single non-Māori category to comprehensively evaluate any significant differences in IoL score that may exist between Māori and non-Māori. Various hierarchical and non-hierarchical cluster analysis techniques were used on the data to see if the patients could be grouped such that patients within the same group were similar to each other. The identified cluster groups were then compared to the ethnic groups, using the measured patient attributes. The expectation-maximisation (EM) algorithm[[15]] was used to fit a finite mixture model to the data and determine the groups to be fitted in the model.

Results

There were 58,648 prioritisation events for cataract surgery spanning four and a half years between November 2014 and March 2019 in the New Zealand public healthcare system. Of these prioritisation events, all had documented CPAC scores but 12,296 did not have the IoL questionnaire component of the score specified and were excluded from analysis. The remaining 46,352 prioritisation events with IoL scores available were included for analysis.

The study population had a mean age of 74.4 years, and had a slight female preponderance (57%). The absolute number and relative proportion of each ethnic group is summarised in Table 1. The average BCVA of the operative eye was 0.73 logMAR (6/32 Snellen equivalent) while the average binocular BCVA was 0.31 logMAR (6/12 Snellen equivalent). The overall mean IoL score was 22.5 (SD 7.8) and the average CPAC score was 59.4 (SD 13.6). The average age, mean IoL score and CPAC scores are summarised by reported ethnicity in Table 1. Māori and Pacific people presented for cataract prioritisation at a younger age (68.5 years and 66.7 years, respectively) compared with all other ethnic groups. There was only a marginal difference when comparing the mean IoL scores of Māori 22.8 (95% CI 22.6, 23.1) and non-Māori 22.4 (95% CI 22.4, 22.5). There was a mean IoL score of 22.9 (SD 7.8) for patients’ first operative eye and 22.3 (SD 7.7) for second operative eye, again with no statistically significant difference between the two groups.

Discriminant analysis and logistic regression demonstrated that for each of the classifiers fitted, 66% to 69% of the observations were correctly classified. Table 3 shows that the majority of individuals with Māori ethnicity were classified with another ethnic group. Models were also fitted where the patients had been reclassified as either Māori or non-Māori. For each of the classifiers, 87 to 90% of the observations were correctly classified. However, it can be seen from Table 4 that the majority of the patients with Māori ethnicity were classified with the non-Māori ethnic group.

Analysis of the groupings identified using cluster analysis demonstrated no relationship between the cluster analysis groups and different ethnicities. The data was also investigated to determine whether subsets of various attributes were more predictive of the ethnicity groups. Mixture model analysis identified six groups when fitting models to each of IoL score and best corrected logMAR binocular vision separately (Table 5), and three groups when using all of the attributes (Table 6). These groups did not correspond to ethnicity. Discriminant analysis was also unable to separate the individuals into the ethnic groups. Models were then fitted with five groups specified. It can be seen in Table 7 and Table 8 that the identified groups also did not correspond to ethnicities. The ethnicities were combined such that the groupings were Māori versus the others. Cluster analysis found three groups in the data for Māori versus the Others. These groups did not correspond to ethnicity. In summary, no statistically significant differences in IoL scores between the ethnic groups including Māori and non-Māori were identified.

Views Tables 1–8.

Visual acuity

Pacific people and Māori were noted to have significantly (p<0.001) worse best corrected visual acuity (95% CI 0.915–0.940 vs 0.688–0.698 for other ethnicities) in the operative eye at prioritisation, when compared with other ethnic groups as outlined in Table 2. Best corrected binocular vision was not significantly different (p=0.834) between ethnic groups (95% CI 0.306–0.319 for Māori and Pacific people vs 0.310–0.316 for other ethnicities).

Discussion

The IoL score comprises 13% of the total CPAC score used to prioritise public-funded cataract surgery in New Zealand. The ability of the IoL to discriminate between eligible patients, and prioritise those who have the greatest need and are most likely to benefit from cataract surgery, is critical to ensure fair and equitable distribution of limited healthcare resources.

There are well established disparities in health status, access to treatment and health outcomes for Māori and Pacific people in New Zealand. The Health and Disability System Review released in June 2020 highlighted the significantly worse health outcomes for Māori, and proposed various strategies to address these disparities.[[16]]

Results of the current study noted that VRQoL, as assessed using the IoL, were very similar for Māori and non-Māori patients presenting with cataract. These results are surprising, as it is well established that Māori have significantly higher rates of non-communicable disease and a higher burden of all-cause morbidity when compared with non-Māori.[[17]] As poor health is closely associated with quality of life, it would be reasonable to expect that Māori responses to the IoL, which is not specific to vision, should reflect the greater morbidity associated with this group. The analysis of the IoL questionnaire responses in the current study suggest that Māori have similar quality of life to non-Māori as reported by the IoL, despite high rates of morbidity in the cataract age group and a sufficiently large population included in the study. This finding is at odds with a large number of studies that have identified significant inequalities for Māori.[[17]] It seems unlikely that Māori and Pacific people enjoy similar quality of life to patients of other ethnicities despite well-established disparities in health status. Visual impairment is closely linked to decreased quality of life, and patients who undergo cataract surgery typically report significant improvements in quality of life following surgery.[[18]] The more likely explanation for the results of the current study is that the IoL is poorly suited to accurately measure quality of life in Māori and/or non-Māori.

A recent study looking at validation of the IoL questionnaire identified major issues with its ability to assess VRQoL in cataract patients.[[4]] The Catquest-9SF, an alternative tool for measuring VRQoL, has been extensively validated for use in assessing VRQoL in New Zealand and elsewhere, and does not have the same accuracy and reliability issues that have been identified with the IoL assessment tool.[[4]] The current study contributes to this growing body of evidence that the IoL questionnaire may be an inappropriate tool for prioritisation of patients for cataract surgery in New Zealand, and in particular, may disproportionally disadvantage Māori and Pacific people who require cataract surgery.

The current study highlights the need for rigorous validation of clinical assessment tools used as a basis for allocation of public-funded healthcare resources. There is a very real risk that poorly validated tools may contribute to widening health inequalities and present barriers to accessing treatment for ethnic minorities.

Summary

Abstract

Aim

The ‘Impact on Life’ (IoL) questionnaire is a patient reported quality-of-life assessment tool used to prioritise cataract surgery in New Zealand (NZ). This study evaluated the association between ethnicity and IoL questionnaire responses.

Method

This is a retrospective cohort study of patients prioritised for public-funded cataract surgery between November 2014 and March 2019 in New Zealand. Data were extracted from the New Zealand Ministry of Health National Prioritisation Web Service database. Ethnic, demographic and IoL data for all patients who were prioritised for surgery were analysed after controlling for age, gender, visual acuity and cataract type.

Results

Of the 58,648 prioritisation events, over the four-and-a-half-year period, 46,352 prioritisation events had documented scores for the IoL questionnaire. The study population had a mean age of 74.4 years and had a female preponderance (74%). The average IoL score was 22.5/36 (SD 7.8). After controlling for age, gender, visual acuity (VA) and cataract type, there was only a marginal difference between Māori and non-Māori IoL scores (22.8/36 vs 22.4/36) despite statistical significance for the difference (p=0.001). Māori and Pacific people presented at a younger age (68.5 years and 66.7 years, respectively) with worse visual acuity than other ethnic groups (mean range 70.1–76.7 years). Mean IoL scores were 23.0/36 for Māori and Pacific people and 22.4/36 for other ethnic groups.

Conclusion

Māori and Pacific people present younger with worse VA and more advanced cataracts at time of surgical prioritisation when compared with other ethnic groups. Despite these differences, after controlling for confounding factors, the mean IoL score did not differ to a level that was clinically significant between different ethnic groups in New Zealand at time of prioritisation for cataract surgery. These results suggest that there are no meaningful ethnic specific differences in patient reported quality of life for patients with cataract in New Zealand after controlling for other factors. Alternatively, the IoL tool may lack the sensitivity to detect meaningful ethnic disparities that may exist for quality of life in this cohort of patients.

Author Information

Nancy Wang: Department of Ophthalmology, University of Auckland, New Zealand. Lyn Hunt: Department of Statistics, University of Waikato, New Zealand. James McKelvie: Department of Ophthalmology, University of Auckland, New Zealand; Department of Ophthalmology, Waikato District Health Board, New Zealand.

Acknowledgements

Correspondence

James McKelvie: Department of Ophthalmology, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. +649 3737 999, fax +649 367 7173.

Correspondence Email

james@mckelvie.co.nz

Competing Interests

Nil.

1) Vision 2020: the cataract challenge. Community Eye Health. 2000;13(34):17-9.

2) Hadorn DC, Holmes AC. The New Zealand priority criteria project. Part 1: Overview. BMJ. 1997 Jan 11;314(7074):131-4.

3) Derrett S, Devlin N, Hansen P, Herbison P. Prioritizing patients for elective surgery: a prospective study of clinical priority assessment criteria in New Zealand. Int J Technol Assess Health Care. 2003 Winter;19(1):91-105.

4) Li SS, Misra S, Wallace H, Hunt L, McKelvie J. Patient-reported quality of life for cataract surgery: prospective validation of the “Impact on Life” and Catquest-9SF questionnaires in New Zealand. N Z Med J. 2019 Oct 4;132(1503):34-45.

5) Nielsen E, Lundström M, Pesudovs K, Hjortdal J. Validation of Catquest-9SF in Danish: developing a revised form of the Catquest-9SF - the Danish Catquest-7SF. Acta Ophthalmol. 2019 Mar;97(2):173-7.

6) Lundstrom M, Behndig A, Kugelberg M, Montan P, Stenevi U, Pesudovs K. The outcome of cataract surgery measured with the Catquest-9SF. Acta Ophthalmol. 2011 Dec;89(8):718-23.

7) Richter GM, Chung J, Azen SP, Varma R, Los Angeles Latino Eye Study Group. Prevalence of visually significant cataract and factors associated with unmet need for cataract surgery: Los Angeles Latino Eye Study. Ophthalmology. 2009 Dec;116(12):2327-35.

8) Shahbazi S, Studnicki J, Warner-Hillard CW. A Cross-Sectional Retrospective Analysis of the Racial and Geographic Variations in Cataract Surgery. PLoS One. 2015 Nov 5;10(11):e0142459.

9) Yoon JJ, Misra SL, McGhee CN, Patel DV. Demographics and ocular biometric characteristics of patients undergoing cataract surgery in Auckland, New Zealand. Clin Experiment Ophthalmol. 2016 Mar;44(2):106-13.

10) Newlands SJ, Hoy BM, Wilson GA. Cataract surgery in Hauora Tairāwhiti and need for improving access for Māori. Clin Experiment Ophthalmol. 2019 Jan;47(1):145-7.

11) Freundlich SEN, McGhee CNJ. Should we be doing more to identify barriers to cataract surgery for Indigenous populations in New Zealand? Clin Experiment Ophthalmol [Internet]. 2020 Jun 21; Available from: http://dx.doi.org/10.1111/ceo.13813.

12) Disney G, Teng A, Atkinson J, Wilson N, Blakely T. Changing ethnic inequalities in mortality in New Zealand over 30 years: linked cohort studies with 68.9 million person-years of follow-up. Popul Health Metr. 2017 Apr 26;15(1):15.

13) New Zealand Ministry of Health. National Ethics Advisory Committee. Ethical Guidelines for Observational Studies: Observational research, audits and related activities. National Ethics Advisory Committee; 2012.

14) New Zealand Ministry of Health. Standard Operating Procedures for Health and Disability Ethics Committees. Wellington (NZ): MOH;2-19 Dec.  

15) Dempster, A.P., Laird, N.M., Rubin, D.B. Maximum Likelihood from incomplete data via the EM algorithm. Journal of the Royal Statistical Society. 1977;39(1):1-38.

16) Health and Disability System Review: Final report – Executive overview. Available from: https://systemreview.health.govt.nz/assets/Uploads/hdsr/health-disability-system-review-final-report-executive-overview.pdf

17) A window on the quality of Aotearoa New Zealand’s health care 2019 | He matapihi ki te kounga o ngā manaakitanga ā-hauora o Aotearoa 2019. Available from: https://www.hqsc.govt.nz/assets/Health-Quality-Evaluation/PR/Window_2019_web_final.pdf

18) Heemraz BS, Lee CN, Hysi PG, Jones CA, Hammond CJ, Mahroo OA. Changes in quality of life shortly after routine cataract surgery. Can J Ophthalmol. 2016 Aug;51(4):282-7.

Contact diana@nzma.org.nz
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