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Editors Selection IGR 23-4

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Comment by Anne Coleman on:

21848 The additional yield of a periodic screening programme for open-angle glaucoma: A population-based comparison of incident glaucoma cases detected in regular ophthalmic care with cases detected during screening, Stoutenbeek R; de Voogd S; Wolfs RC et al., British Journal of Ophthalmology, 2008; 92: 1222-1226

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Stoutenbeek and colleagues present a thoughtful and thought-provoking article on the benefit of population-screening for open-angle glaucoma (OAG). The authors analyzed data from the Rotterdam Eye Study incidence study to determine the benefit of periodic screening to prevent glaucoma blindness in the Netherlands. Twenty- three (23) of 78 (29%) incident OAG cases had been diagnosed six years after the baseline survey and were under care. Undetected cases were less likely to have Goldmann visual field (GVF) loss (47%) than those who had been detected (83%) and only 4/55 had missed ten or more points in both eyes on an automated suprathreshold visual field test. The authors estimated (making assumptions about life expectancy and progression rates) that the number of persons that would have to be screened to prevent one case of bilateral blindness is about 1,000.

The number of persons that would have to be screened to prevent one case of bilateral blindness is about 1,000

One critical assumption made by the authors that has to be questioned is that preventing blindness in one or both eyes is the only goal of glaucoma screening. Recent studies indicate that both selfreported quality of life and objective measures of patient function are affected prior to blinding visual field loss. Preventing these losses of function is a benefit of identifying and treating persons with OAG earlier in the disease process.

The authors argue that those who have more severe OAG are more likely to be under care, putting into question the benefit of screening programs. The Netherlands has an excellent national healthcare system making it more likely that eye exams will be performed and people with more severe OAG will be identified (as was the case in this study). Countries with less successful health systems may not identify OAG at the same rate without focused screening efforts. In addition, those who had been identified with OAG in the present study had larger cup:disc ratios at baseline. While the authors state that only those who had high eye pressures at baseline were notified of the need for follow-up, it is possible that some with large cup:disc ratios were alerted to this fact and therefore were more likely to obtain care. These individuals may therefore have been diagnosed because they had participated in the baseline study, and also may have been more likely to develop GVF loss over follow-up.

The number of persons that would have to be screened to prevent one case of bilateral blindness is about 1,000

The authors point to important issues that need to be recognized and considered when determining how aggressively to screen for glaucoma. Often the most severe cases make it to care and more mild cases remain undiagnosed, limiting the value of screening since most with mild glaucoma will not suffer severe visual field loss. However, lesser degrees of field loss can affect quality of life. Periodic screening for eye disease in general rather than for glaucoma alone would almost certainly be more cost-effective and could overcome some of the concerns raised in the Stoutenbeek and colleagues paper.

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