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Editors Selection IGR 7-3
Epidemiology
Comment by Paul Healey on:
13147 Validity of screening for glaucomatous optic nerve damage using confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph II) in high-risk populations: a pilot study, Harasymowycz PJ; Papamatheakis DG; Fansi AK et al., Ophthalmology, 2005; 112: 2164-2171
Glaucoma has several features that make it an important public health problem; it is relatively common, largely undiagnosed, irreversible and generally asymptomatic until very late in the disease. Not surprisingly, it is a major cause of blindness worldwide. Harasymowycz et al. (760) ask whether we can improve diagnosis rates by using scanning laser ophthalmoscopy to screen for glaucomatous optic neuropathy in high-risk populations. To answer this question, the authors performed a cross-sectional study which recruited subjects considered to be at high risk for glaucoma. These participants were subjected to two diagnostic test series, an HRT II optic nerve head scan and a clinical examination by one of the authors. No functional tests such as perimetry were performed. So the comparator for the HRT was simply the opinion of the ophthalmologist as to whether a patient had structural features suggestive of glaucoma. Upon clinical examination, a large proportion (7.2%) of the sample was thought to have glaucomatous optic neuropathy. If this were the true prevalence of glaucoma, it would compare only with the Barbados Eye Study amongst population-based studies that used the gold standard glaucoma diagnosis of structural and functional abnormality independent of intraocular pressure. The agreement between clinical examination and HRT II MRA was found to be poor. This is in keeping with previous studies. The poor agreement between the HRT and clinical examination highlights the differences in diagnostic technique between imaging devices and clinical examination. While the HRT assessment is based strictly on comparative rim area measurements, the clinical examination was not specified. Previous studies suggest clinicians are not so reliable at estimating rim area or cup-disc ratio. Doctors do excel in assessing qualitative signs and matching them to patterns of disease state acquired over many years of clinical experience. But without independent verification of glaucoma using both structural and functional measures, we do not know which of the two techniques compared in this study most accurately identify subjects with glaucoma.
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