Five years may be optimum screening interval for open-angle glaucoma
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In a study using two different methods of analysis, the preclinical detectable phase for open-angle glaucoma was estimated to be approximately 10 years, suggesting that a reasonable screening interval could be 5 years.
The study was conducted on a large population screened for glaucoma in Malmö, Sweden, between 1992 and 1997. Of the 42,497 individuals invited to participate, 32,918 aged 57 to 77 years were screened. Individuals were classified as positive at screening when at least one of the following criteria was fulfilled: IOP greater than 25 mm Hg in one or both eyes; suspected or evident glaucomatous optic disc, retinal nerve fiber defects or optic disc hemorrhages seen in fundus photographs; exfoliation syndrome; or manifest glaucoma in one or more first-degree relatives. Data were then collected on the incidence of new cases after the screening.
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The preclinical detectable phase (PCDP), also known as sojourn time, is the mean time from which glaucoma can be detected by screening to its clinical diagnosis, and it is an important parameter for planning screening programs. In the study, the length of the mean PCDP was calculated by the classic method of dividing the prevalence of screening-detected glaucoma with the clinical incidence and by using a Markov chain Monte Carlo model simulation that derived both the length of the mean PCDP and the sensitivity of the screening. The two methods yielded similar results, with a mean estimate of approximately 10 years.
“Our results suggest that screening for open-angle glaucoma, if repeated, could be done with relatively long intervals, eg, 5 years,” the authors wrote.
Importantly, the authors noted that these results may not be applicable in all countries because the study population was predominantly white.
“Results should be most useful in Europe-derived populations,” they said.
Perspective
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This study estimates, on average, the preclinical detectable phase (PCDP), ie, the period of time for which glaucoma may be detected in an individual using a screening test before it would be diagnosed otherwise. Using two different methods, the estimate of PCDP for glaucoma was 10 years. This can help inform the interval between tests for any future population screening program for glaucoma.
At present, there is a lack of evidence supporting that general population screening for glaucoma is cost-effective. However, the possibility of targeted screening of people at high genetic risk for glaucoma and artificial intelligence-supported screening test assessment may mean screening will become cost-effective in the future. This study will provide evidence for developing the screening test intervals.
We need high-quality prospective evidence that population screening for glaucoma can be cost-effective. This may be through targeting people at high risk for glaucoma rather than screening the whole general population above a certain age.
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