All Publications

  • Longitudinal changes in global cataract surgery rate inequality and associations with socioeconomic indices CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Yan, W., Wang, W., van Wijngaarden, P., Mueller, A., He, M. 2019; 47 (4): 453–60


    Cataract is the leading cause of blindness and the second leading cause of vision impairment. The majority of people with vision impairment reside in low-resource settings with limited access to cataract surgery and services.Cataract surgery rate (CSR) is a proxy measure for eye care service delivery and estimating the burden of cataract disease. This research aims to evaluate the longitudinal changes of CSR inequality globally and by income groups.Systematic review.Studies published from January 2000 to December 2015 were considered for inclusion into the review.CSR data were retrieved from a systematic review of published literature (OVID Medline, Embase, PubMed, ISI, Web of Science), unpublished reports and data repositories.Inequality of CSR was measured on a global scale and between countries grouped by income levels using the Gini coefficient and concentration index, with respect to the human development index (HDI).Overall, correlations between HDI and gross domestic product (GDP) per capita vs CSRs were observed with R2 values of 49.2% (β = 5.01, P < 0.001) and 38.9% (β = 0.56, P < 0.001), respectively. Analysis of longitudinal CSR data using generalized estimation equation models revealed strong associations between CSR and HDI (P < 0.001), GDP (P < 0.001) and the proportion of people aged ≥50 (P = 0.001). Overall, the trend of inequality in worldwide CSR remained relatively stable.Inequalities in cataract service provision were found between countries grouped by income and associated with socioeconomic indicators.

    View details for DOI 10.1111/ceo.13430

    View details for Web of Science ID 000471831500005

    View details for PubMedID 30362287

  • Association of Socioeconomics With Prevalence of Visual Impairment and Blindness JAMA OPHTHALMOLOGY Wang, W., Yan, W., Mueller, A., Keel, S., He, M. 2017; 135 (12): 1295–1302


    Vision loss is the third most common impairment worldwide. Although cost-effective interventions are available for preventing or curing most causes of vision loss, availability of these interventions varies considerably between countries and districts. Knowledge of the association between vision loss and socioeconomic factors is informative for public health planning.To explore correlations of the prevalence of visual impairment with socioeconomic factors at country levels and to model and estimate a socioeconomic-adjusted disease burden based on these data.In this cross-sectional study, the following data were collected from 190 countries and territories: the age-standardized prevalence of moderate to severe visual impairment (MSVI) and blindness from January 1 to December 31, 2010, across countries, human development index (HDI), gross domestic product (GDP) per capita, total health expenditure, total health expenditure as percentage of GDP (total health expenditure/GDP), public health expenditure as percentage of total health expenditure (public/total health expenditure), and out-of-pocket expenditure as percentage of total health expenditure (out-of-pocket/total health expenditure). Countries were divided into 4 levels (low, medium, high, and very high) by HDI. Data analysis was conducted from September 1, 2016, to July 1, 2017.The correlations between prevalence data and socioeconomic indices were assessed.A strong negative association between prevalence rates of MSVI and blindness and socioeconomic level of development was observed. The mean (SD) age-standardized prevalence of MSVI decreased from 4.38% (1.32%) in low-HDI regions to 1.51% (1.00%) in very-high-HDI regions (P < .001). The national HDI level was attributable to 56.3% of global variation in prevalence rates of MSVI and 67.1% of global variation in prevalence rates of blindness. Higher prevalence rates were also associated with lower total health expenditure per capita, total health expenditure/GDP (β = −0.236 [95% CI, −0.315 to −0.157] for prevalence of MSVI; β = −0.071 [95% CI, −0.100 to −0.042] for prevalence of blindness), public/total health expenditure (β = −0.041 [95% CI, −0.052 to −0.031] for prevalence of MSVI; β = −0.014 [95% CI, −0.018 to −0.010] for prevalence of blindness), and higher percentage of out-of-pocket/total health expenditure (β = 0.044 [95% CI, 0.032-0.055] for prevalence of MSVI; β = 0.013 [95% CI, 0.009-0.017] for prevalence of blindness). Countries with increased burden of visual impairment and blindness can be easily identified by the results of the linear models. Socioeconomic factors could explain 69.4% of the global variations in prevalence of MSVI and 76.3% of the global variations in prevalence of blindness.Burden of visual impairment and socioeconomic indicators were closely associated and may help to identify countries requiring greater attention to these issues. The regression modeling described may provide an opportunity to estimate appropriate public health targets that are consistent with a country’s level of socioeconomic development.

    View details for DOI 10.1001/jamaophthalmol.2017.3449

    View details for Web of Science ID 000418056800007

    View details for PubMedID 29049446

    View details for PubMedCentralID PMC6583541

  • A Global View on Output and Outcomes of Cataract Surgery With National Indices of Socioeconomic Development INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE Wang, W., Yan, W., Mueller, A., He, M. 2017; 58 (9): 3669–76


    Cataract blindness accounts for a substantial proportion of blindness worldwide. Understanding the correlations between national levels of socioeconomic development with the quantity and quality of cataract surgery may provide insight for the prioritization and resource allocation for blindness prevention programs.The relationships between human development index (HDI), gross domestic product (GDP) per capita, and cataract surgical coverage (CSC) and visual outcome of cataract surgery were examined in a multinational study utilizing secondary data from the repository for Rapid Assessment of Avoidable Blindness (RAAB), World Health Organization, Global Burden of Disease, United Nations, and the World Bank.A total of 266 RAAB studies across 73 countries/territories were retrieved. Linear regression model results revealed strong associations of HDI with prevalence of cataract blindness (β = -7.056, P < 0.001), CSC (β = 60.808, P = 0.004), proportion of intraocular lens (IOL) implantation (β = 87.040, P = 0.001), and proportion of cases with good vision outcomes among operated eyes (β = 73.351, P < 0.001) in studies performed between 1995 and 2009. Similar associations were observed for studies performed between 2010 and 2015. In addition, countries with lower GDP per capita showed a higher rate of cataract blindness (β = -0.527, P = 0.001), lower CSC (β = 9.800, P < 0.001), lower percentage of IOL implantation (β = 6.871, P = 0.001), and fewer patients with good vision outcomes after surgery (β = 7.959, P < 0.001). After controlling survey year, country, and other factors, GDP per capita and HDI were also found to be significantly associated with CSC and visual outcomes after cataract surgery (all P < 0.05).We documented the strong associations of socioeconomic indices with quantity and quality of cataract surgery. These socioeconomic indicators should be considered as important factors for developing strategies aimed to improve worldwide cataract surgery service delivery.

    View details for DOI 10.1167/iovs.17-21489

    View details for Web of Science ID 000410931200045

    View details for PubMedID 28728174

  • Predictive Medicine in Ophthalmology OPHTHALMOLOGY Yan, W., He, M. 2017; 124 (4): 420–21

    View details for DOI 10.1016/j.ophtha.2016.12.018

    View details for Web of Science ID 000397850600021

    View details for PubMedID 28335932

  • What Twin Studies Have Taught Us About Myopia. Asia-Pacific journal of ophthalmology (Philadelphia, Pa.) Chen, Y. n., Wang, W. n., Han, X. n., Yan, W. n., He, M. n. ; 5 (6): 411–14


    Myopia has become epidemic, particularly in East Asia, and is a major cause of visual impairment worldwide. Twin studies are an important resource to investigate the genetics and the gene-environment interaction in myopia. This article aims to provide an overview of major findings regarding myopia from different types of twin studies, from the heritability of myopia-related traits to novel findings of genome-wide association studies. In the postgenomic era, twin studies will continue to serve as a unique method in the investigation of gene-environment interaction.

    View details for DOI 10.1097/APO.0000000000000238

    View details for PubMedID 27898444

  • Utilisation and perceptions towards smart device visual acuity assessment in Australia: a mixed methods approach BMJ OPEN Keel, S., Scheetz, J., Holloway, E., Han, X., Yan, W., Mueller, A., He, M. 2019; 9 (3): e024266


    To investigate mobile health product use in Australia and societal and clinician perceptions towards smartphone based visual acuity (VA) assessment tools.Quantitative analysis of a cross-sectional survey delivered to the general public and thematic analysis of in-depth interviews of eye health clinicians.Online survey within Australia and face-to-face in-depth interviews of clinicians.1016 adults were recruited via Survey Monkey Audience, social media (Facebook and Twitter), Rotary Australia and Lions Clubs Australia. Six clinicians were recruited from private and public settings in Melbourne, Australia.The study assessed socio-demographic characteristics, history of mobile health product use and perceived advantages and potential drawbacks of smartphone based VA assessment tools.A total of 14.4% of the study population had previously used a mobile-based health product. After adjusting for covariates, younger age (p=0.001), male gender (p=0.01) and higher income (>$45 000) were associated with increased likelihood of having used a mobile health product (p=0.005). Seventy-two per cent of participants would use an automated smartphone based VA assessment tool, provided that the accuracy was on par to that of human assessors. Convenience (37.3%) and cost-savings (15.5%) were ranked as the greatest perceived advantages. While test accuracy (50.6%), a lack of personal contact with healthcare providers (18.3%) and data security (11.9%) were the greatest concerns. Themes to emerge from clinician qualitative data included the potential benefits for identifying refractive error in patients, as well as the ability to self-monitor vision. Concerns were raised over the potential misuse of self-testing vision apps and the inability to detect pathology.Our findings suggest that a substantial proportion of the Australian population do not use mobile health products. Furthermore, there remains notable concerns, including test accuracy and data privacy, with smartphone-based VA assessment tools by both clinicians and the public.

    View details for DOI 10.1136/bmjopen-2018-024266

    View details for Web of Science ID 000471144900117

    View details for PubMedID 30904849

    View details for PubMedCentralID PMC6475225

  • Ten-year changes of intraocular pressure in adults: the Liwan Eye Study CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY Han, X., Zhao, H., Wu, C., Liu, C., Yan, W., Hu, Y., He, M. 2019; 47 (1): 41–48


    Understanding the longitudinal intraocular pressure (IOP) changes and potential risk factors in adults is important for future glaucoma control in the aging society.Limited longitudinal studies exist in Asia investigating the longitudinal IOP changes and with varying results.Population-based cohort study.1405 baseline participants from the Liwan Eye Study.All baseline participants were invited for the 10-year follow-up examination in 2013. IOP (by Tonopen), central corneal thickness (CCT; by ultrasound), refractive error (by autorefractor), blood pressure, height and weight were measured per standardized protocol and the presence of hypertension or diabetes was collected by questionnaire. Follow-up examinations were conducted using the same equipment with proper calibration. Linear regression analysis was used to assess the association between IOP change and potential risk factors.10-year IOP change.Of the 791 participants at the 10-year follow-up, IOP data were available for 602 participants with a mean age of 60.9 years (55.5% female). The average IOP change over 10 years was an increase of 1.44 mmHg (95% confidence interval, 1.12-1.75). Linear regression showed that 10-year IOP change was not associated with baseline age, gender, body mass index (BMI), CCT, spherical equivalence (SE), hypertension or diabetes. However, it was positively associated with longitudinal increase of BMI when longitudinal changes of BMI and SE were included in the model (P < 0.001).We observed a small increase in IOP over 10 years in this adult Chinese population, which was positively related to the longitudinal change in BMI.

    View details for DOI 10.1111/ceo.13372

    View details for Web of Science ID 000458614400007

    View details for PubMedID 30091181

  • Longitudinal changes in intraocular pressure and association with systemic factors and refractive error: Lingtou Eye Cohort Study BMJ OPEN Han, X., Yang, T., Zhang, J., Yu, S., Guo, X., Yan, W., Hu, Y., He, M. 2018; 8 (2): e019416


    To investigate the longitudinal changes in intraocular pressure (IOP) and its associations with refractive error and systemic determinants in a Chinese geriatric population.Prospective cohort study.Guangzhou Government Servant Physical Check-up Center, Guangzhou, China.4413 government employees aged no less than 40 years (41.9% female) attending annual physical and eye examinations were included in this study. The inclusion criterion was having attended the 2010 follow-up examination. The exclusion criteria include glaucoma or intraocular surgery history, IOP >21 mm Hg at any visit or without available IOP data at all visits from 2010 to 2014.The outcome measure was IOP at each follow-up visit from 2010 to 2014. Mixed-effect model was used to assess the relationship between longitudinal changes in IOP and potential risk factors.For the 2653 participants who had available IOP data at both the 2010 and 2014 follow-up visits, the average change in IOP was an increase of 0.43 (95% CI 0.36 to 0.50) mm Hg. For the whole study population and in the optimised mixed model, there was a non-linear increase of IOP with age (P<0.001), with greater changes in younger subjects and in women (P<0.001 and P=0.002, respectively). Elevations in systolic blood pressure, diastolic blood pressure, body mass index (BMI) and fasting plasma glucose (FPG), as well as a myopic shift (all with P<0.001), during the follow-up were associated with an increasing trend of IOP, while serum lipids were found to be not significantly associated.In this cohort of elderly Chinese adults, IOP increases non-linearly with ageing. People with increasing blood pressure, BMI, FPG and myopic progression are more likely to have IOP elevation over time.

    View details for DOI 10.1136/bmjopen-2017-019416

    View details for Web of Science ID 000433129800133

    View details for PubMedID 29444785

    View details for PubMedCentralID PMC5829881

  • Prevalence of age-related macular degeneration in rural southern China: the Yangxi Eye Study BRITISH JOURNAL OF OPHTHALMOLOGY Jin, G., Ding, X., Xiao, W., Xu, X., Wang, L., Han, X., Xiao, O., Liu, R., Wang, W., Yan, W., An, L., Zhao, J., He, M. 2018; 102 (5): 625–30


    To describe the prevalence of age-related macular degeneration (AMD) among older adults in rural southern mainland China.Eligible persons aged 50 years or over were identified by geographically defined cluster sampling from Yangxi County, Guangdong Province, China. Participants underwent a standardised interview and comprehensive eye examinations from August to November in 2014. Digital retinal photographs were graded for AMD lesions using the Clinical Classification of Age-Related Macular Degeneration developed by the Beckman Initiative for Macular Research Classification Committee. Age-standardised prevalence of AMD and AMD lesions was calculated using the 2010 world population data and compared with those of other populations.Of 5825 subjects who participated (90.7% response rate), 4881 (83.8%) had fundus photographs gradable for AMD. Early, intermediate and late AMD were present in 2003 (41.0%), 879 (18.0%) and 42 (0.86%) participants. The age-standardised prevalence of early, intermediate and late AMD was 40.4% (95% CI 39.6% to 41.2%), 17.6% (95% CI 17.0% to 18.2%) and 0.79% (95% CI 0.65% to 0.95%), respectively. Total AMD was more prevalent in men than in women (62.8% vs 57.1%).AMD is an important public health concern for rural southern China, and the prevalence of AMD was higher in men than in women.

    View details for DOI 10.1136/bjophthalmol-2017-310368

    View details for Web of Science ID 000430439800008

    View details for PubMedID 28848023

  • Prevalence and risk factors of epiretinal membranes: a systematic review and meta-analysis of population-based studies BMJ OPEN Xiao, W., Chen, X., Yan, W., Zhu, Z., He, M. 2017; 7 (9): e014644


    This study was to aggregate the prevalence and risks of epiretinal membranes (ERMs) and determine the possible causes of the varied estimates.Systematic review and meta-analysis.The search strategy was designed prospectively. We searched PubMed, Embase and Web of Science databases from inception to July 2016. Reference lists of the included literatures were reviewed as well.Surveys published in English language from any population were included if they had a population-based design and reported the prevalence of ERM from retinal photography with or without optical coherence tomography. Eligibility and quality evaluation was conducted independently by two investigators.The literature search generated 2144 records, and 13 population-based studies comprising 49 697 subjects were finally included. The prevalence of ERM and the ORs of potential risk factors (age, sex, myopia, hypertension and so on) were extracted.The pooled age-standardised prevalence estimates of earlier ERM (cellophane macular reflex (CMR)), advanced ERM (preretinal macular fibrosis (PMF)) and any ERM were 6.5% (95% CI 4.2% to 8.9%), 2.6% (95% CI 1.8% to 3.4%) and 9.1% (95% CI 6.0% to 12.2%), respectively. In the subgroup analysis, race and photography modality contributed to the variation in the prevalence estimates of PMF, while the WHO regions and image reading methods were associated with the varied prevalence of CMR and any ERM. Meta-analysis showed that only greater age and female significantly conferred a higher risk of ERMs.Our findings suggest that ERMs are relatively common among aged population. Race, image taking and reading methodology may play important roles in influencing the large variability of ERM prevalence estimates.

    View details for DOI 10.1136/bmjopen-2016-014644

    View details for Web of Science ID 000412650700022

    View details for PubMedID 28951399

    View details for PubMedCentralID PMC5623383

  • Progression of Near Vision Loss and Incidence of Near Vision Impairment in an Adult Chinese Population OPHTHALMOLOGY Han, X., Ellwein, L. B., Guo, X., Hu, Y., Yan, W., He, M. 2017; 124 (5): 734–42


    To investigate the progression of near vision loss and the cumulative incidence of near vision impairment (NVI) 6 years after initial examination of an urban Chinese cohort.Population-based, prospective cohort study.People aged ≥35 years examined at baseline in the Yuexiu District of Guangzhou, China.Participants examined at baseline were invited for 2-year and 6-year follow-up examinations in 2010 and 2014, respectively. Examinations included noncycloplegic autorefraction and binocular near visual acuity (NVA) with and without current near correction measured at 40 cm using a LogMAR ETDRS near vision tumbling E chart. Those with uncorrected binocular NVA (UCNVA) ≤20/40 underwent subjective refraction to obtain best-corrected binocular NVA (BCNVA).Change in UCNVA between baseline and 2014 follow-up examinations and the 6-year cumulative incidence of vision impairment based on 3 definitions: NVA ≤20/40, ≤20/50, and ≤20/63.Among the 1817 baseline participants, 1595 (87.8%) were reexamined in 2010 and 1427 (78.5%) in 2014. Mean vision loss between baseline and the 2014 follow-up was 1.54 (±1.74) lines of UCNVA. Vision loss was associated with age 80 years or older, less education, and better baseline UCNVA. The 6-year cumulative incidence of uncorrected binocular NVI (UCNVI) across the 3 vision impairment definitions was 55.2% (95% confidence interval [CI], 46.1%-64.3%), 51.3% (95% CI, 44.0%-58.7%), and 42.4% (95% CI, 35.5%-49.3%), respectively. With best-corrected binocular NVI (BCNVI), incidence was 6.89% (95% CI, 4.28%-9.50%), 5.17% (95% CI, 2.89%-7.44%), and 2.62% (95% CI, 1.11%-4.12%), respectively. A higher incidence of UCNVI was associated with worse baseline UCNVA for all 3 impairment definitions. Similarly, incidence of BCNVI was associated with worse baseline BCNVA, but also with older age and education at the primary level or less. Gender was not significant for either UCNVI or BCNVI.Approximately half of those aged 35 years or older develop UCNVI in 6 years, the overwhelming majority of whom can be corrected with spectacles. Cost-effective strategies to provide spectacles to this at-risk population remains an issue requiring further study.

    View details for DOI 10.1016/j.ophtha.2017.01.020

    View details for Web of Science ID 000402402400028

    View details for PubMedID 28336059

    View details for PubMedCentralID PMC6053595

  • Cataract Surgical Rate and Socioeconomics: A Global Study. Investigative ophthalmology & visual science Wang, W. n., Yan, W. n., Fotis, K. n., Prasad, N. M., Lansingh, V. C., Taylor, H. R., Finger, R. P., Facciolo, D. n., He, M. n. 2016; 57 (14): 5872–81


    Cataract is the leading cause of blindness and cataract surgical rate (CSR) is used as a proxy indicator of access to cataract services in a country. The aim of this study was to explore the associations between the CSR and the economic development of countries in terms of gross domestic product per capital (GDP/P) and gross national income per capita (GNI/P).We systematically searched OVID (Medline and Embase), Pubmed,, ISI Web of Science, and Cochrane Library databases, and retrieved additional data from unpublished reports. Cataract surgical rates and economic indicators (GDP/P, GNI/P) were collected for each country from 2005 to 2014. Complete data were used for the 50 largest countries according to World Health Organization (WHO) population estimates. Linear correlations between GDP/P and CSR were calculated. Cataract surgical rate data over two periods were used for analysis: 2005 to 2009 and 2010 to 2014 (CSR in 2009 or nearest year, CSR in 2014 or nearest year).Over the study period, CSR data were available for 152 countries across both time periods. Most of the CSR data were obtained from nongovernment organization (NGO) reports, including WHO reports. A good linear correlation between CSR and GDP/P was found overall, nearest to 2009 (β = 0.162, Linear: y = 0.162x + 282.242; R2 = 0.665, P < 0.001). Regression analysis of CSR nearest to 2014 produced similar findings, with significant correlations between CSR and GDP/P (Linear: y = 0.208x + 94.008; R2 = 0.785, P < 0.001). When using GNI/P as an economic indicator, similarly excellent lines of fit were obtained. After adjusting for time and country, CSR was significantly associated with GDP/P (Coefficient = 0.147, R2 = 0.759, P < 0.001), and GNI/P (Coefficient = 0.152, R2 = 0.757, P < 0.001). Most countries had an increase in CSRs over time, with the greatest increases observed for Iran and Argentina.Cataract surgical rate and economic indicators are closely associated, indicating the strong influence of resource availability on healthcare delivery. Considering this relationship, it is important to be innovative in delivery of low-cost services and invest strategically in capacity development to meet cataract surgical need in low-resource settings.

    View details for DOI 10.1167/iovs.16-19894

    View details for PubMedID 27802517

  • Green-laser induced maculopathy in a 15-year-old boy. Journal of AAPOS : the official publication of the American Association for Pediatric Ophthalmology and Strabismus Yan, W. n., Chakrabarti, R. n., Little, M. n., Carden, S. M. 2016; 20 (3): 258–60


    We report the case a 15-year-old boy who presented with retinopathy caused by a green-diode (class IIIB) laser. The patient was followed over a period of 8 weeks. Visual acuity on day 1 was 6/7.5, with central scotoma in the right eye, and 6/5 in the left eye. Macular optical coherence tomography of the right eye day 1 showed focal subfoveal disruption of the photoreceptor ellipsoid and myoid zones extending through the external limiting membrane to the outer nuclear layer. At week 8, visual acuity was 6/6 right eye and 6/5 in the left eye. Disruption of the ellipsoid and myoid layers, though still present, had improved.

    View details for DOI 10.1016/j.jaapos.2015.11.016

    View details for PubMedID 27060667

  • Age-Related Changes of Intraocular Pressure in Elderly People in Southern China: Lingtou Eye Cohort Study. PloS one Han, X. n., Niu, Y. n., Guo, X. n., Hu, Y. n., Yan, W. n., He, M. n. 2016; 11 (3): e0151766


    To study age-related changes of intraocular pressure (IOP) and assess the cohort effect in both cross-sectional and longitudinal settings among elderly Chinese adults.Participants were enrolled from the Lingtou Eye Cohort Study with Chinese government officials aged 40 years and older at baseline and received physical check-up and ocular examinations from 2010 to 2012. IOP was measured using a non-contact tonometer according to standardized protocols, as well as systolic blood pressure (SBP), diastolic blood pressure (DBP) and body mass index (BMI). Participants who had attended IOP measurements in both 2010 and 2012 were included in this study. Cross-sectional association of IOP with age was assessed using multivariate liner regression analyses and based on the data of 2010. Longitudinal changes in IOP were assessed by paired t-test.A total of 3372 subjects were enrolled in the current analysis (2010 mean [SD] age, 61.9 [7.1] years; 60.2% men). The mean IOP in 2010 was 15.4 ± 2.3 mmHg for women and 15.2 ± 2.3 mmHg for men with an intersex difference (P = 0.029). Cross-sectional analysis showed that IOP was negatively associated with age (P = 0.003, β = -0.033 for women and P<0.001, β = -0.061 for men) adjusted for baseline SBP, DBP and BMI. Paired t-test suggested that IOP was higher in the year 2012 than 2010 in women (P = 0.006) but did not change significantly in men within 2 years (P = 0.345). In addition, the 2-year changes of IOP were not associated with age adjusted for baseline IOP in 2010 (P = 0.249).Cross-sectional data suggests that IOP is lower in people with older age. Longitudinal data does not support such findings and thus the identified decreasing pattern with age in cross-sectional analysis is likely caused by cohort effects.

    View details for DOI 10.1371/journal.pone.0151766

    View details for PubMedID 26986222

    View details for PubMedCentralID PMC4795753