Visual function rather than visual acuity – Authors' reply
Authors: Fatima Kyari, Rupert R A Bourne, Peng T Khaw, David S Friedman, Nathan Congdon, Jacqueline Ramke, Matthew J Burton
Journal: The Lancet Global Health (2021)

We would like to thank Ian Murdoch and David Crabb for their important letter pointing out the tendency to underestimate the global burden of glaucoma when focusing solely on central vision loss. Glaucoma is the leading cause of irreversible vision loss globally, whose share of overall blindness prevalence has been growing steadily as investments have begun to pay off in the fight against diseases such as cataract and trachoma.1Burton MJ Ramke J Marques AP et al.The Lancet Global Health Commission on Global Eye Health: vision beyond 2020.Lancet Glob Health. 2021; 9: e489-e551Summary Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 2Bourne R Steinmetz JD Flaxman S et al.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. 2021; 9: e130-e143Summary Full Text Full Text PDF PubMed Scopus (56) Google Scholar We fully agree that reliance only on central vision as an index of disease severity is particularly poorly suited to accurately estimating the glaucoma burden.3Tham YC Li X Wong TY Quigley HA Aung T Cheng CY Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis.Ophthalmology. 2014; 121: 2081-2090Summary Full Text Full Text PDF PubMed Scopus (2499) Google Scholar Glaucoma has already done substantial harm to the eye and to visual function by the time central vision is affected. Activities such as safe driving might become impossible because of loss of peripheral vision from glaucoma, long before central vision is affected.4Blane A Through the looking glass: a review of the literature investigating the impact of glaucoma on crash risk, driving performance, and driver self-regulation in older drivers.J Glaucoma. 2016; 25: 113-121Crossref PubMed Scopus (16) Google Scholar Other substantial underestimates also result from this approach. As pointed out in the Lancet Global Health Commission, many individuals with early glaucoma need timely treatment to avoid later vision loss and certain high-risk groups, such as adults aged 40 years and older and people of African descent, require screening care for the same reason.1Burton MJ Ramke J Marques AP et al.The Lancet Global Health Commission on Global Eye Health: vision beyond 2020.Lancet Glob Health. 2021; 9: e489-e551Summary Full Text Full Text PDF PubMed Scopus (50) Google Scholar All of these demands on the health-care system are missed when we account for the magnitude of glaucoma solely using central vision loss as a measure. Besides more inclusive and sensitive measures of glaucoma prevalence and the disease's health-care implications, we would also like to highlight again the following pressing needs in the global response to glaucoma, as outlined in the Commission: (1) low-cost screening outreach models for low-income and middle-income countries—eg, leveraging existing cataract outreach efforts and eye-screening programmes for patients with diabetes; (2) trials of cost-effective, scalable, and locally acceptable glaucoma treatments that are appropriate for low-resource settings, such as low-cost laser trabeculoplasty; (3) rigorous studies of inexpensive interventions to improve knowledge about and demand for glaucoma care in underserved areas; (4) capacity strengthening among eye-care professionals, particularly in sub-Saharan Africa and east Asia, where the magnitude of glaucoma blindness is especially high, to improve skills in glaucoma detection and management with appropriate resourcing of ongoing chronic care that is stratified by risk of vision loss; and (5) evidence-based advocacy to governments to include glaucoma in national eye health planning. We fully agree with Murdoch and Crabb that global efforts to reduce the glaucoma burden depend heavily on an accurate and inclusive accounting of its precise extent. We cannot fight what we do not know. NC reports professional fees from Belkin Laser. All other authors declare no competing interests. The Lancet Global Health Commission on Global Eye Health: vision beyond 2020Eye health and vision have widespread and profound implications for many aspects of life, health, sustainable development, and the economy. Yet nowadays, many people, families, and populations continue to suffer the consequences of poor access to high-quality, affordable eye care, leading to vision impairment and blindness. Full-Text PDF Open AccessVisual function rather than visual acuityWe would like to express our gratitude to Matthew Burton and colleagues for the Commission on Global Eye Health (April, 2021),1 which highlights the magnitude of the challenge. As a plea we would like to mention the glaucomas. We feel this preventable cause of blindness has been insufficiently represented and the burden of this disease group understated because of the use of visual acuity alone to measure disability. Full-Text PDF Open Access