Pointwise linear regression for evaluation of visual field outcomes and comparison with the advanced glaucoma intervention study methods

Objective: To investigate pointwise linear regression (PLR) for longitudinal evaluation of visual fields and to compare results with those of the Advanced Glaucoma Intervention Study (AGIS) criteria. Methods: We selected 509 eyes (401 patients) from the AGIS,with 3 or more years of follow-up, 7 or more visual field examinations, and an AGIS reference score of 16 or lower. Visual field change at test locations was defined as a change of threshold sensitivity of 1 dB/y or higher and P less than or equal to .01. Several sets of criteria were investigated for defining change of visual field series with PLR. Main Outcome Measures: Progression or improvement of visual field series with PLR and AGIS criteria. Results: Mean (SD) follow-up time and baseline AGIS score were 7.4 (1.7) years and 7.7 (4.4), respectively. Pairwise agreement between AGIS and various PLR criteria ranged from 52% to 64% with the kappa statistic varying between 0.22 (95% confidence interval, 0.15-0.29) and 0.30 (95% confidence interval, 0.22-0.38). One hundred thirty-eight (27%) and 151 (30%) eyes progressed (85 eyes or 17% detected by both methods) while 72 (14%) and 11 (2%) eyes improved (5 eyes or 1% detected by both methods) based on AGIS and the most rigorous PLR criteria, respectively. Conclusions: Based on rigorous, clinically relevant criteria, PLR detects progression in a similar proportion of eyes compared with AGIS criteria. Pointwise linear regression may be superior to AGIS methods since it identifies fewer visual field series as improving.