Prediction of repeatable glaucomatous visual field defects based on cluster characteristics.

Abstract

Aim: This study evaluates if characteristics (eg, location, size, volume) of clusters of defects on an initial visual field (VF) test were predictive of a repeatable defect in the subsequent two tests.

Methods: Retrospective cohort study of 197 eyes of 103 patients with healthy, suspect or early glaucoma. Using the initial VF pattern deviation probability grid, we defined the number of clusters (≥1 location of p<5%) and associated size (number of adjoining defect locations) and volume (sum of corresponding total deviation values) for each cluster stratified by the four probability levels (ie, p<5%; p<2%; p<1% and p<0.5%).

Results: Of 4424 locations with a defect of p<5%, only 1189 (26.9%) were repeatable. The size [area under the receiver operating characteristic curve (AUC) 0.80, CI 0.76 to 0.85)] and volume (AUC 0.80, CI 0.76 to 0.85) of clusters were predictive of a repeatable defect within the cluster. The optimal thresholds for predicting a repeatable location within each cluster at 95% specificity based on initial cluster size were >6 locations at p<5%, >4 locations at p<2%, >3 locations at p<1% and >2 locations at p<0.5%. Defining cluster defects by involvement of central or peripheral rim locations improved the predictive value compared with the entire 24-2 grid.

Conclusion: The location, size and volume of clusters of defects on an initial VF test may be predictive of subsequent repeatability. This may help distinguish eyes with a higher risk of repeatable defects.