Classification of Visual Field Abnormalities in the Ocular Hypertension Treatment Study

Abstract

THE OCULAR Hypertension Treatment Study (OHTS) is a randomized clinical trial to evaluate the safety and efficacy of topical hypotensive medication in delaying or preventing the onset of primary open-angle glaucoma (POAG) in participants with ocular hypertension. The onset of POAG is defined as either the development of reproducible visual field loss (as determined by the visual field reading center) and/or reproducible optic nerve damage (as determined by the optic disc reading center) attributed to POAG. The OHTS Endpoint Committee determines POAG and is masked to the participant's randomization assignment. A detailed description of the OHTS protocol and manual of procedures^1-3 as well as the baseline visual field characteristics for the OHTS⁴ participants have been previously published. Recent articles by Kass et al⁵ and Gordon et al⁶ have been published regarding the outcome of the OHTS. In addition, we have reported that 86% of first-occurring abnormal visual fields in the OHTS were not confirmed on the next retest.⁷ Originally, the OHTS criterion for reproducibility of a visual field abnormality was 2 consecutive abnormal visual fields with the abnormality in the same location and on the same index. However, in June 1997, the abnormality criterion was changed to 3 consecutive abnormal fields with the abnormality in the same location and on the same index. In this article, we describe a novel system for classifying the types of visual field defects(glaucomatous and nonglaucomatous; reproducible and not reproducible) and report the frequency of these defects during follow-up in the OHTS by their classification.