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Subspecialties Health Economics and Policy, Comprehensive, Cataract, Glaucoma, Pediatric, Refractive, Retina, Diabetes

A Way Out of the Dark

Why collect health data unless you can use it effectively and make it available to everyone who could benefit? The Vision Loss Expert Group (VLEG) answered that key question by publishing the estimated numbers of people suffering from blindness and vision impairment worldwide in The Lancet Global Health in February 2021 (1, 2). Our ongoing work, supported by several charities, is in collaboration with the Global Burden of Disease (GBD) Study, which is funded by The Bill and Melinda Gates Foundation. At the 20th Anniversary of the GBD in 2017, attended by members of VLEG, Bill Gates explained how his aim was to make disability data “actionable" (see Figure below). 

This article, featuring leading experts – and including the World Health Organization and International Agency for Prevention of Blindness – explains the vision disability data that has underlined the 20-year VISION 2020 WHO Initiative, the progress made, and the actions needed to meet the challenges ahead.

At the 20th Anniversary of the GBD in 2017, attended by members of VLEG, Bill Gates explained how his aim was to make disability data “actionable.”
WHO’s Universal Eye Health Global Action Plan 2019-2014 (3).

VISION 2020: The Right to Sight and WHO Report on Vision

VISION 2020: The Right to Sight, the joint global initiative for the elimination of avoidable blindness of the WHO and the International Agency for the Prevention of Blindness, has been important in increasing awareness of avoidable blindness and has resulted in the establishment of regional and national entities that facilitate a broad range of activities. The adoption of a resolution entitled “Towards Universal Eye Health: A Global Action Plan 2014–2019” by the 66th World Health Assembly opened up a new opportunity for member states to progress with their efforts to prevent visual impairment and strengthen rehabilitation of the blind in their communities. As the period of the WHO’s Global Action Plan 2014–2019 (3) came to an end, it became clear that the 25 percent reduction in avoidable blindness has not yet been met – largely because of aging populations.

WHO’s World Report on Vision (4).

In 2019, the WHO published the World Report on Vision (4). The report provides evidence on the magnitude of eye conditions and vision impairment globally (provided by VLEG), draws attention to effective strategies to address eye care, and offers recommendations for action to improve eye care services worldwide. The key proposal of the report is for all countries to provide integrated people-centered eye care services that ensure people receive a continuum of eye care based on their individual needs throughout their lives.

VLEG and the Global Vision Database

For the past 13 years, VLEG has curated a Global Vision Database that contains prevalence data on vision impairment and blindness by cause from published (and some unpublished) population-based surveys of eye disease since 1980. More than 100 members of VLEG worldwide contribute the regional expertise to select only high-quality studies with samples representative of the population and with clearly defined visual acuity testing protocols. VLEG has analyzed this data to provide prevalence estimates (with 95 percent uncertainty intervals (UI)) for 2010, 2015, and now 2020. Definitions are as follows:

Levels of visual impairment Presenting visual acuity*
Mild vision impairment ≥6/18 and <6/12
Moderate and severe vision impairment (MSVI) <6/18 to 3/60
Blindness <3/60 or less than 10° visual field around central fixation
Vision impairment from uncorrected presbyopia Presenting near vision <N6 or <N8 at 40 cm where best-corrected distance visual acuity is ≥6/12

*Presenting visual acuity means the visual acuity measured in the better eye using the corrective lenses brought to the appointment in the eye survey

Prior to this project there was no accessible data resource for blindness and vision impairment figures by country worldwide. Occasional WHO estimates were not sex-specific and only reported for two age groups, with no facility for estimating temporal change in the burden of vision loss.

Millions affected by blindness and vision impairment in 2020

In 2020, an estimated 43·3 million (95 percent UI 37·6–48·4) people were blind. We estimated 295 million (267–325) people to have moderate and severe vision impairment (MSVI); 258 million (233–285) to have mild vision impairment; and 510 million (371–667) to have visual impairment from uncorrected presbyopia. Fifty-five percent of people in each of these groups were female. Since 1990, blindness has increased by 50 percent and the number of individuals with moderate and severe vision impairment has risen by 92 percent. Importantly, however, if one adjusts for the change in the age structure of the world’s population over that time (by age-standardization), the age-standardized prevalence of blindness has decreased in adults aged 50+ by 29 percent – a very positive message for advocacy. The same cannot be said for the prevalence of mild and moderate vision impairment, which barely changed.

The causes of blindness and vision impairment are changing

As countries move up the spectrum of development, more people live into adulthood, the average age of the population increases, and the disease burden shifts to noncommunicable diseases and disabilities. The vast majority of ocular disease burden is noncommunicable, so eye diseases occupy an increasing share of the overall disease burden. In 2020, cataracts remained the most common cause of blindness in those aged 50+ (83 million people), followed by glaucoma (3.6 million), under corrected refractive error (2.3 million), AMD (1.8 million), and diabetic retinopathy (0.86 million). In terms of moderate and severe vision impairment, under corrected refractive error affected 86.1 million people followed by cataracts (78.8 million).

A unique aspect of VLEG’s work has been the ability to look at the changing contribution to vision loss over the last three decades. Although the number of affected people increased for blindness due to all modeled causes, age-standardized prevalence for all modeled causes of vision except diabetic retinopathy has decreased over the past three decades. This suggests that eye care services did successfully reduce age-standardized prevalence, but they did not meet the increasing needs of an aging and growing population.

Conclusions and future expectations

The work of this international collaboration has demonstrated the considerable inter-regional differences that exist and highlighted areas that require particular attention, such as blindness caused by diabetic retinopathy.

Regional-level data might be misleading – masking the diversity of existing situations within countries and even within communities. We need greater sociodemographic granularity in data collection to identify the populations most at risk and to capture actual progress in the provision of equitable eye care services.

The recently published work by VLEG and GBD for 2020 is a major update of global and regional data on the causes of prevalence of blindness and vision impairment and adds to our understanding of temporal change over 30 years.

Our group has highlighted a need for more data on the causes of vision impairment; we found data sources to be sparse, particularly in children and young adults, high-income locations, and in sub-Saharan Africa. Moreover, up-to-date, population-representative data from high-income settings has lagged behind. Better age and geographical data coverage would allow for more detailed analyses of individual country differences and a breakdown of which diseases most impact vision in children.

The recently published work by VLEG and GBD for 2020 is a major update of global and regional data on the causes of prevalence of blindness and vision impairment and adds to our understanding of temporal change over 30 years. Over the past decade, the prevalence of avoidable visual impairment has decreased in older adults, but it has not reached the target reduction delineated in the WHA GAP. The principal reason from a global perspective is the failure of eye care services to keep pace with the aging and growing populations; however, the reduction in age-standardized prevalence of blindness caused by cataract, glaucoma, age-related macular degeneration, and under corrected refractive error was a reassuring step in the right direction.

For more information on reports and data, go to globalvisiondata.org.


To read a detailed overview of the vision loss status in seven super-regions of the world, prepared by leading epidemiologists...

... click here

 


Data and Advocacy

Ian Tapply, an ophthalmologist from Cambridge University Hospital, UK, working with VLEG, explains how to access the data while Peter Holland, CEO, and Jessica Crofts-Lawrence, Head of Policy and Advocacy at the International Agency for Prevention of Blindness, London, UK, explain how it is used for advocacy.

The Global Vision Database is an extensive and up-to-date source of 0phthalmic epidemiological data maintained and continuously updated by the Vision Loss Expert Group (VLEG). A key ethos of the VLEG is the dissemination of data to inform and drive policy that can improve the lives of those affected by, or at risk of, vision loss. To this end, the five-yearly reports, the most recent published in Lancet Global Health in February 2021 (1, 2) provide actionable data at the country and the global level. These findings are also summarized in a Lancet Global Commission on Global Eye Health to be published in late February 2021. These papers enable us to review progress and forecast trends for the future. The progress in reducing avoidable visual impairment in the over-50s during the past decade is laudable, although it is disappointing that the targeted 25 percent reduction set by the World Health Assembly global action plan (WHA GAP) was not met. The global demographic changes forecast for the next 30 years, with the numbers of over-65s rising from 1 billion to 2 billion, highlight the importance of keeping pace with population eye care needs.

The information contained in the database has been made accessible through the Vision Atlas (5) by VLEG’s collaboration with the International Agency for the Prevention of Blindness (IAPB). This extensive resource enables the user to visualize the burden of visual loss at country, regional, and supra-regional level. Changes in these figures from 1990 onwards can also be accessed. Country-level demographic data and availability of trained eye-care professionals is also available. The Atlas is therefore a powerful tool to access and use the extensive data.

The Vision Atlas and underpinning data have been critical in advancing the global policy agenda for eye health. The VLEG data provided the foundation for the WHO’s first World Report on Vision, endorsed by all countries. The data have also enabled organizations, such as the IAPB, to make the case for the importance of eye health to all, and to demand greater action of governments. The visual presentation of the data in the Vision Atlas has enabled advocates to make the case for eye health to governments around the world. A year-long advocacy campaign drawing on the VLEG data and the Vision Atlas led to the World Health Assembly adopting in August 2020 a resolution on integrated people-centered eye care, making eye care an integral part of the journey toward Universal Health Coverage.

Global map of age-standardized prevalence of blindness, 1990-2020. Source: Vision Atlas (5).

Members of the Department of Noncommunicable Diseases, specializing in sensory loss, offer the WHO’s perspective

By Stuart Keel, Technical Officer: Vision and Eye Care Programme, Department of Noncommunicable Diseases, and Alarcos Cieza, Unit Head, Blindness and Deafness Prevention, Disability and Rehabilitation, WHO, Geneva, Switzerland

The recently published estimates on the magnitude and causes of vision impairment offer important insights into the effectiveness of public health strategies and new treatments in the field over the past decades, as well as highlighting a number of remaining challenges in eye care. In the global context, the take home messages are clear:

i) unoperated cataract and uncorrected refractive error remain major items on the agenda of public health;

ii) new strategies are needed to cater to the comprehensive and long-term health system requirements associated with the rapid emergence of noncommunicable chronic eye conditions, such as diabetic retinopathy, glaucoma, age-related macular degeneration, and complications of myopia.

The World Health Assembly (WHA) resolution titled ‘Integrated people-centered eye care, including preventable vision impairment and blindness’ adopted by Member States in 2020 aims to stimulate action to address many of these key challenges and sets forth concrete actions to make eye care an integral part of Universal Health Coverage (UHC).

As the eye care sector transitions from “VISION 2020: The Right to Sight” to these new strategies in the coming years, several opportunities also exist to strengthen the type of data that is collected in epidemiological surveys. Firstly, as recommended in the WHO World report on vision (2019), it is important that the field moves away from reporting solely on the “presenting” vision impairment (vision with spectacles or contact lenses if worn to the assessment) to also report on “uncorrected” vision impairment (without spectacles or contact lenses) given individuals with refractive errors have an ongoing need for eye care services and therefore information on both the unmet and the met needs are important to plan services. Secondly, to effectively target the eye care needs of people at critical periods throughout the life course, data on the magnitude and causes of vision impairment in younger populations requires strengthening. Addressing these data gaps will mean that the evidence generated from epidemiological surveys can be more effectively used to drive policy decisions around eye care service planning.


Gender and Vision Impairment

By ME Hartnett, Distinguished Professor, Calvin S. and JeNeal N. Hatch Presidential Endowed Chair in Ophthalmology and Visual Sciences, Vitreoretinal Medical and Surgical Service, University of Utah, USA

With the ability to analyze data specifically by sex, the VLEG found that females bore the greater burden of vision impairment and blindness. Age-standardized prevalence of blindness and vision impairment were greater for women due to cataract, under corrected refractive error, age-related macular degeneration, and diabetic retinopathy, greater only for men due to glaucoma. Although age-standardized prevalence of blindness decreased overall from 1990 to present, the decrease in burden of vision loss was lower for women than for men. In addition, for those with moderate and severe vision impairment, the minimal change in prevalence (an increase of about 2.5 percent for those over age 50 years) was largely due to a greater increase among females (4.27 percent) than males (0.35 percent). When considering mild and moderate and severe vision loss, global age-standardized prevalence increased for women.

Cataract and refractive error are avoidable causes of vision impairment, as defined by the World Health Assembly, because there are ways to effectively treat these with surgery or glasses. Outreach screening has helped with equity of access for cataract surgery among underserved groups, including women and the elderly, but there is still more to be done. Additional studies are needed to understand the reasons for these sex disparities, particularly in more complex and less easily treatable conditions like diabetic retinopathy, glaucoma, and age-related macular degeneration. Diabetic retinopathy was found to be the only cause of vision loss and blindness studied with a global increase in age-standardized prevalence between 1990 and 2020. This is particularly concerning as the number of people with diabetes and diabetic retinopathy is projected to increase in the coming years.

More research is also needed to fully understanding why there are sex discrepancies in all categories of vision loss in both high- and low- to middle-income countries in order to improve outcomes. It is important to note that the causes for discrepancies may vary depending on collective wealth. For example, in low- and middle- income countries, difficulties can exist in diagnosing and delivering care to patients; however, in high-income countries, management of chronic age-related conditions may be more common. Nonetheless, additional research is necessary to probe for the causes of discrepancies across levels of vision loss and across economies. The work of VLEG is very important to develop research protocols and request funding for continued important work.


Experts with decades of experience in vision loss prevention episodes share their view on challenges and opportunities for the future

By Hugh Taylor, Melbourne Laureate Professor at the University of Melbourne, and Serge Resnikoff, Professor at University of New South Wales Sydney in Kensington, Australia

We face some real challenges for the future. In 1999, when Vision 2020: The Right to Sight was launched by WHO and the IAPB, it was estimated that the number of blind people in 1990 was approximately 38 million and that, without targeted programs, the number would more than double by 2020 to 90 million. However, if preventable blindness was properly addressed that number could be reduced dramatically to 25 million. Although Vision 2020 achieved a great deal, the number of blind people in 2020 is 43 million. Both population growth and the increased aging of the population have led to this large number, although the prevalence of blindness in those aged 50 years and above has been reduced by 29 percent from 25.8 percent in 1990 to 18.5 percent in 2020. We see similar issues with MSVI, although the numbers here are much larger with 295 million affected.

We do know what to do to reduce most preventable vision loss; for example, a pair of spectacles can correct refractive vision loss immediately, and vision is restored overnight by cataract surgery.

When we look at the projections for 2050, we can see a significant increase, with estimates of 61 million blind people and some 474 million with MSVI. Clearly, there is a large challenge and much to be done. The recently released World Report on Vision from the WHO builds on the plans of VISION 2020 and emphasizes the need for the integration of eye care into universal health care. Care must be affordable, accessible, and appropriate. There is a strong need for government planning and oversight. It focuses on integrated person-centered eye care with the need for coordination between primary, secondary, and tertiary eye care services so the patient’s journey or the pathway of care is seamless.

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  1. GBD 2019 Blindness and Vision Impairment Collaborators; Vision Loss Expert Group of the Global Burden of Disease Study, “Causes of blindness and vision impairment in 2020 and trends over 30 years, and prevalence of avoidable blindness in relation to VISION 2020: The Right to Sight: an analysis for the Global Burden of Disease Study,” Lancet Glob Health, 9, e144 (2021). PMID: 33275949.
  2. GBD 2019 Blindness and Vision Impairment Collaborators; Vision Loss Expert Group of the Global Burden of Disease Study, “Trends in prevalence of blindness and distance and near vision impairment over 30 years: an analysis for the Global Burden of Disease Study,” Lancet Glob Health, 9, e130 (2021). PMID: 33275950.
  3. WHO, “Universal Eye Health Global Action Plan 2019-2014.” 
  4. WHO, “World Report on Vision.” 
  5. IAPB Vision Atlas, “1.1 billion people live with vision loss,” (2020). 

About the Author

Rupert Bourne

Consultant Ophthalmic Surgeon and Lead for the Vision Expert Group. He’s based in Cambridge, UK.

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