Risk factors for visual field progression in the groningen longitudinal glaucoma study: a comparison of different statistical approaches.

PURPOSE

To identify risk factors for visual field progression in glaucoma and to compare different statistical approaches with this risk factor analysis.

PATIENTS AND METHODS

We included 221 eyes of 221 patients. Progression was analyzed using Nonparametric Progression Analysis applied to Humphrey Field Analyzer data. Risk factors were analyzed using the statistical approaches from the Advanced Glaucoma Intervention Study, the Early Manifest Glaucoma Trial, and the Canadian Glaucoma Study. Four intraocular pressure (IOP) variables (baseline IOP, mean IOP during follow-up, IOP fluctuation, and pretreatment IOP) and 8 other risk factors were investigated.

RESULTS

On average, 7.1 reliable fields were available after a mean follow-up of 5.3 years; 89 eyes progressed. With the Advanced Glaucoma Intervention Study approach, age [odds ratio (OR) 1.03/y; 95% confidence interval (CI), 1.00-1.06; P = 0.044] predicted progression. With an additional stepwise selection procedure, mean IOP during follow-up (1.16 per mm Hg; 1.05-1.29; P=0.003),baseline HFA mean deviation (MD; 2.72 for worse versus better than --6 dB; 1.50-4.95; P=0.001) and age (1.03; 1.01-1.06;P=0.010) predicted progression [corrected]. With the Early Manifest Glaucoma Trial approach, baseline IOP [hazard ratio (HR) 1.07; 95% CI, 1.02-1.11; P = 0.010], baseline Frequency Doubling Perimeter MD (HR = 1.75; 95% CI, 1.14-2.70; P = 0.013), and age (HR = 1.03; 95% CI, 1.01-1.05; P = 0.006) predicted progression. Finally, with the Canadian Glaucoma Study approach, baseline IOP (HR = 1.07; 95% CI, 1.02-1.11; P = 0.010), baseline Frequency Doubling Perimeter MD (HR = 1.75; 95% CI, 1.14-2.70; P = 0.013), and age (HR = 1.03; 95% CI, 1.01-1.05; P = 0.006) predicted progression.

CONCLUSIONS

IOP, disease stage, and age seemed to be robust independent risk factors for visual field progression in glaucoma. The IOP variable that was significant depended on the statistical approach applied.