Abstract
Purpose: :
To investigate risk factors for visual field progression in glaucoma and to compare 3 different statistical approaches for this analysis.
Methods: :
Two hundred twenty-one eyes of 221 glaucoma patients were included, followed prospectively with standard automated perimetry (Humphrey Field Analyzer) in the Groningen Longitudinal Glaucoma Study, an observational cohort study. Progression was assessed with Nonparametric Progression Analysis (NPA) and Glaucoma Progression Analysis (GPA). Risk factors were analysed using the statistical approaches used in the Advanced Glaucoma Intervention Study (AGIS), Early Manifest Glaucoma Trial (EMGT) and Canadian Glaucoma Study (CGS).
Results: :
On average 7.2 reliable fields were available after a mean follow-up of 5.4 years. Of 221 eyes, 89 and 65 showed progression according to the NPA and the GPA algorithms, respectively. With the AGIS approach, age (OR 1.03 per year increase; 95% confidence interval 1.00-1.06; P=0.041) was predictive for NPA progression. If a stepwise variable selection was added to the AGIS approach, intraocular pressure (IOP) fluctuation during follow-up (OR 1.27 per mmHg increase; 1.08-1.50; P=0.004), worse baseline FDT test result (number of abnormal test locations; OR 1.08 per test location; 1.03-1.13; P=0.004) and older age (OR 1.04; 1.01-1.06; P=0.005) predicted NPA progression. With the EMGT approach, worse baseline IOP (HR 1.07 per mmHg; 1.02-1.11; P=0.003), worse baseline FDT test result (HR 1.05; 1.01-1.08; P=0.011) and older age (HR 1.03; 1.01-1.05; P=0.009) predicted NPA progression. With the CGS approach, worse baseline IOP (HR 1.07; 1.03-1.12; P=0.001), worse baseline HFA mean deviation (worse than -6 dB; HR 1.71; 1.10-2.65; P=0.018) and older age (HR 1.03; 1.01-1.05; P=0.012) predicted NPA progression. The only risk factors found for GPA progression were a positive family history for glaucoma (AGIS approach; OR 2.19; 1.01-4.72; P=0.046) and mean IOP during follow-up (CGS approach; HR 1.10; 1.01-1.20; P=0.029).
Conclusions: :
IOP, disease stage and age seem to be significant independent risk factors for visual field progression in glaucoma. Results may depend on both the statistical approach applied and the outcome measure used.
Keywords: clinical (human) or epidemiologic studies: risk factor assessment • clinical research methodology • perimetry