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Editors Selection IGR 16-4

Clinical examination methods: Progression analysis and visual field

Comment by Stuart Gardiner & Chris Johnson on:

12489 Bayes' theorem applied to perimetric progression detection in glaucoma: from specificity to positive predictive value, Jansonius NM, Graefe's Archive for Clinical and Experimental Ophthalmology, 2005; 243: 433-437

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In glaucoma, one of the most important questions is whether damage is progressing or stable. Longitudinal series of visual fields from perimetry can be analysed in a variety of ways, and the best analysis has yet to be definitively determined. Three main factors need to be considered when comparing analysis techniques; specificity, sensitivity and predictive power. Jansonius (<543) uses permutation theory to determine the theoretical specificity and predictive power of an analysis that ranks the series of fields into order according to severity of damage. Such an analysis is simpler to interpret because it does not involve assessing the magnitude of the difference between any given pair of fields. Unfortunately, ranking a series of fields is in itself a challenging and certainly non-trivial task, and the establishment of specific criteria for determining progression versus stability of the visual field. One index may indicate worsening while another indicates improvement. Therefore to translate these results into a practical setting, it will first be necessary to devise a comprehensive set of rules to determine the ranking order of the fields. The work of Jansonius provides a solid, valid theoretical basis for determining visual field progression, but the practical implementation of this approach remains to be examined to establish its clinical value.

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