Factors Associated With Long-Term Visual Field Variability in Patients With Normal-Tension Glaucoma.

Purpose: To investigate the factors associated with variability in the longitudinal visual field (VF) test in patients with normal-tension glaucoma (NTG). Methods: This retrospective study enrolled patients with NTG who underwent ≥ 12 reliable VF tests over a follow-up period of ≥ 6 years. For each eye, 52 total deviation values (TDVs) were linearly regressed against time (years), while the root-mean-squared error (RMSE) of the residuals was calculated to quantify the long-term VF variability. Hierarchical cluster analysis using squared Spearman correlation coefficients was conducted to assess collinearity and select variables. Six linear mixed-effects models were constructed, each including clinical parameters such as intraocular pressure (IOP), retinal nerve fiber layer thickness (RNFLT), and VF parameters. Mixed-effects regression was applied to evaluate the factors associated with long-term VF variability, adjusting for intereye correlation. Results: The study analyzed 114 eyes of 77 patients with NTG. In models including baseline RNFLT, lower baseline IOP, lower mean IOP, greater IOP fluctuation, thinner baseline RNFLT, and a steeper mean deviation (MD) slope were significantly associated with increased long-term VF variability (all Conclusions: Lower baseline and mean IOP, greater IOP fluctuation, thinner baseline RNFLT, worse baseline MD, and steeper MD slope are all associated with a greater long-term VF variability in patients with NTG. NTG eyes with thin RNFL or rapid VF deterioration may require more frequent VF testing to avoid misinterpreting fluctuation as true progression.