Beyond Vision 2020

New trends in population eye disease research can drive better care globally. Howard Larkin reports

As demand for eye services grows with an aging world population, new strategies in eye research can help drive improvements in eye care that better address global need and inequality, according to panellists at the Association for Research in Vision and Ophthalmology 2021 Annual Meeting (ARVO).

To a large extent, the recent shift to epidemiology datadriven eye care policy results from the work of the Vision Loss Expert Group (VLEG). This coalition of more than 100 ophthalmologists and optometrists around the world has transformed eye disease data collection and analysis from an ad hoc exercise into a scientific tool, according to Rupert Bourne BSc, FRCOphth, MD, VLEG coordinator, head of the Glaucoma Service at Cambridge University Hospital, and director of the Cambridge Eye Research Centre, UK.

Before 2010, the World Health Organisation (WHO) released infrequent updates on the prevalence of blindness and vision impairment, reporting sporadic, often incomplete studies supporting no-sex, limited age, and cause disaggregation, Dr Bourne said. Since 2010, VLEG has conducted a systematic, regular review of the published and grey literature used to create The Global Vision Database, which now has more than 500 population-based eye surveys.

This supports new analysis every five years to note changes in prevalence rates worldwide and individual countries and regions. Multiple studies offering microdata are particularly important for age fitting and sex disaggregation, which in turn supports accurate modelling of the current, unmet need and developing needs, Dr Bourne said.

BURDEN OF DISEASE Sophisticated statistical modelling and prevalence estimates also support and validate the Global Burden of Disease (GBD) study, which is particularly important for mobilising resources to address medical needs of all types. The GBD applies disability weights to prevalence, yielding disability-adjusted life years (DALYs). This important health metric allows for burden of disease analysis across 369 disease and injury categories for allocating resources to address it.

The latest GBD report, published in 2019, showed DALYs ranking for blindness and vision loss as nineteenth and fifteenth among all causes for populations 50 to 74 years old and 75 years and older, respectively. These impairments ranked lower than the ninth and tenth place ranking for hearing loss, though together when considered as “sensory loss”, they rank fifth and sixth of all causes of disease burden in these age groups—an even higher disease burden than diabetes.

“The burden [of vision loss] is still very high despite the relatively low disability weight ascribed to it by the GBD,” Dr Bourne said.

According to VLEG’s latest five-year study in 2020, more than 600 million people around the world are blind or at least mildly distance-vision impaired, while another half a billion are near-vision impaired, Dr Bourne reported. Cataract is the leading cause of blindness, and uncorrected refractive error the leading cause of moderate to severe vision impairment. Diabetic retinopathy is the one cause where age-standardised blindness prevalence rates have increased over the last 30 years. (Lancet Global Health, February 2021)

REFINING DATA COLLECTION Non-visually significant ocular morbidities—such as latent glaucoma or conjunctivitis—also contribute to the global burden of eye disease by increasing the need for prevention and monitoring, noted Nathan Congdon MD, MPH, glaucoma specialist and Ulverscroft Professor of Global Eye Health at Queen’s University Belfast, Northern Ireland, UK. He is conducting a review to estimate how much this increases the need for eye care globally.

Among current needs are standardisation of terminology and robust definitions so the impact of these conditions can be better measured and addressed, Dr Congdon said.

“Healthcare planning to serve the population must take into account the full burden of need for eye care. We can’t fight what we can’t see and don’t know.”

Population-based studies contact people who might not otherwise be using medical services and are important to complete the need and burden picture, said Tasanee Braithwaite MPH, MRCP, FRCOphth, DM, Consultant Ophthalmologist at Guy’s and St Thomas’ Hospital, London, UK. She discussed new STROBEVision extension guidelines for standardising the design, conduct, and reporting of such surveys.

Addressing social determinants of health in studies and analysis is yet another critical factor for successfully addressing vision and eye health equity, said Jinan Saaddine MD, MPH, medical epidemiologist at the Vision Health Initiative of the US Centers for Disease Control and Prevention, Atlanta, Georgia, USA. Factors including neighbourhood conditions, access to health services, and social status (including race and ethnicity, education, and economic stability) profoundly affect health risks and inequities and must be taken into account in policy development.

But better data is only the first step, noted Serge Resnikoff MD, PhD, visiting professor at the University of New South Wales, Sydney, Australia. With more than one billion people affected by vision-impairing conditions that in principle are easily addressable, “an absolutely massive upscale of services is really needed very urgently,” he said.

Advances in how vision impairment is defined—including adding near vision impairment to the ICD coding system—helps better define the scope of the problem, Dr Resnikoff added. But much more remains to be done to ensure universal coverage is truly universal, leaving no one behind.

Rupert Bourne: rb@rupertbourne.co.uk Nathan Congdon: n.congdon@qub.ac.uk Tasanee Braithwaite: tasaneebraithwaite@gmail.com Jinan Saaddine: jsaaddine@cdc.gov Serge Resnikoff: serge.resnikoff@gmail.com