The collaborative initial glaucoma treatment study: baseline visual field and test-retest variability

Abstract

Purpose: To compare the baseline Collaborative Initial Glaucoma Treatment Study (CIGTS) visual field (VF) score and mean deviation (MD), investigate test-retest variability, and identify variables associated with VF loss and VF measurement variability.

Methods: Baseline data from a randomized clinical trial of 607 patients with newly diagnosed open-angle glaucoma were collected at 14 clinical centers. The CIGTS VF score and MD were obtained from 24-2 VF tests (Zeiss-Humphrey Systems, Dublin, CA) at two visits approximately 2 weeks apart.

Results: Although most baseline CIGTS VF scores showed limited field loss, 15% (91/607) of patients showed a substantial deficit (VF score >10 on a 0-20 scale). A small but significant learning effect was seen over the two baseline measures for CIGTS VF score and MD. CIGTS VF score and MD correlate highly (r = -0.93); both have high test-retest correlation (0.83 and 0.91, respectively). Variables associated with greater baseline VF loss for both CIGTS VF score and MD include (probabilities for VF only): male sex (P = 0.018), black race (P <or= 0.0001), lower visual acuity (P <or= 0.0001), higher intraocular pressure if more than 30 mm Hg (P = 0.0034), poor field reliability score (P <or= 0.0001), cardiovascular disease (P = 0.015), reduced patient-reported alertness (P = 0.023), and CIGTS clinical center (P <or= 0.0001). Predictors of increased CIGTS VF score variability include a midrange VF score (P <or= 0.0001), first-tested eye (P = 0.0027), reduced patient-reported alertness (P = 0.0177), increasing age (P = 0.0040), current smoker (P = 0.0014), and CIGTS clinical center (P = 0.0215).

Conclusions: The CIGTS VF score provides a measure of VF strikingly similar to the MD. Variables associated with VF loss and VF variability may help identify patients who need greater clinical scrutiny.