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Editors Selection IGR 13-4

Glaucoma as Cause of Blindness: Global variations in glaucoma detection

Comment by Franz Grehn on:

92010 The Global Extent of Undetected Glaucoma in Adults: A Systematic Review and Meta-analysis, Da Soh Z; Yu M; Betzler BK et al., Ophthalmology, 2021; 0:

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This paper reviews the present literature (55 population-based studies) to give a current estimate of how many manifest glaucomas (POAG, PACG, SG) were found that were previously undetected. This question was worked up for geographical region, for ethnicity, for POAG versus all glaucoma (manifest glaucoma), for Human Development Index (HDI), and for Ethnicity. A prognosis is given for the year 2040.

Globally, more than 70% of cases remain undetected on average according to this study. This clearly indicates the problem of lack of symptoms of POAG in early or moderate stages even in health systems with high standards (Glaucoma: 'the silent thief of sight'). In general, glaucoma detection remains mainly opportunistic in most countries. It is noteworthy that according to the Early Manifest Glaucoma Trial, the extent of visual field defects was twice as high when glaucoma was detected in clinics as compared to those which were detected in a screening program. This fact makes the following findings of population studies even more relevant.

The percentage of undetected manifest glaucoma was 94,1% for Africa, 83,9% for Asia, 67,7% for Europe, and 61.9% for North America, respectively.

When assembled according to ethnicity, the numbers are similar: Africans 91.5%, Asians 83.9%, Europeans 66.8%.

When assembled according to Human development Index (HDI), the highest proportion was with the lowest index (94.6%), but even in the highest Index (≥ 0.80), the percentage of undetected glaucoma was 71.4%. This means that ethnicity and geographical area have a higher impact on percentage of undetected glaucomas than HDI.

When taking Europe as a reference level, the highest odds ratio was found in Africa (12.7), and in Asia (3,41), whereas some countries had better odds ratios than Europe, such as USA (0,61), but the difference was not significant in the latter. This means that the proportion of undetected glaucoma is 12x higher in Africa than in Europe.

The absolute numbers of known or previously undetected manifest glaucoma or POAG cases are 52,7 million detected versus 43.8 million undetected worldwide in 2020. These numbers will increase in 2040 by demographic changes to 79.8 million and 67.1 million, respectively. Asia alone accounts for 58.4% of undetected glaucoma, a number that will increase by 53.2% to 67.1 million undetected cases. The largest increase of undetected glaucoma will occur in Africa with 86,3% (from 8.02 to 14.92 million).

In Asia as in most regions, there is a difference between urban and rural areas by a factor of two worse in rural areas. The lack of accessibility of eye care services in areas of deprivation is significantly associated with delay in detection of glaucoma.

The reported meta-analysis calls for 'a paradigm shift from a passive opportunistic casefinding approach to a more proactive screening strategy. Although the cost of mass screening for glaucoma has been cited as a debilitating factor, cost-effective population-based screenings have been reported in China and India' and should be considered also in more developed areas of the world. Artificial intelligence for detecting glaucomatous optic nerve disease might redefine the approach to better glaucoma detection strategies.

This article is in particular helpful for arguing with politicians in countries where systematic preventive glaucoma eye care is not covered by the public insurance system or is considered not helpful or even harmful by some officials. The paper closes with the following appeal: 'The problem of glaucoma detection is not new, and its ill effects will only exacerbate with continued inertia. Therefore, it is time to take action.'

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