Objective: The purpose of the study is to develop alternative statistical approaches for evaluating the trend of visual field series over time and to compare the results to human observers.
Design: Retrospective analysis of visual field results.
Participants: Eighty-three eyes of 83 patients (phakic or pseudophakic) with open-angle glaucoma and 5 or more eligible fields were included in the study.
Intervention: Three experienced observers independently reviewed the field series to determine stability or progression.
Main outcome measures: The following additional methods to determine progression of visual field loss were used: (1) pointwise univariate regression analysis and a glaucoma change analysis; (2) univariate regression analysis on visual field indices mean deviation, corrected loss variance, and glaucoma pattern index; (3) pointwise multivariate regression analysis with fixed effects on panel data; and (4) clusterwise multivariate regression analysis with fixed effects on panel data. The results of different statistical methods were compared by determining the pairwise agreement (Cohen's weighted kappa) between each technique and three experienced observers.
Results: Patients were observed for a mean (+/-standard deviation) of 5.6 (+/-1.4) years. The visual fields of 27 (33%) and 56 (67%) eyes were considered to have progressed or remained stable, respectively, based on agreement of at least 2 of 3 observers. Univariate regression analysis on visual field indices was not useful for detection of visual field progression. Pointwise and clusterwise regression analyses with fixed effects on panel data performed as well as pointwise univariate regression analysis compared with human observers (kappa = 0.52, 0.53, and 0.55, respectively). Both methods showed better agreement with human observers than with glaucoma change analysis (kappa = 0.41).
Conclusions: A new statistical model, multivariate regression analyses with fixed effects on panel data, is an appropriate method to evaluate the course of visual field series over time and shows reasonable agreement with experienced observers and pointwise univariate regression analysis.