The groningen longitudinal glaucoma study III. The predictive value of frequency-doubling perimetry and GDx nerve fibre analyser test results for the development of glaucomatous visual field loss

Abstract

To investigate whether frequency-doubling perimetry (FDT) and nerve fibre analyser (GDx) test results are able to predict glaucomatous visual field loss in glaucoma suspect patients. A large cohort of glaucoma suspect patients (patients with ocular hypertension or a positive family history of glaucoma without visual field abnormalities at baseline) was followed prospectively for 4 years with SAP (HFA 30-2 SITA fast), FDT (C-20 full threshold), and GDx (version 2.010) in a clinical setting. After the follow-up period, baseline FDT and GDx test results of converters (glaucoma suspect patients who had converted to a reproducible abnormal SAP test result during follow-up) were compared to that of non-converters (suspects with normal SAP test results at the end of the follow-up) by calculating relative risks. Cutoff point for FDT was >1 depressed test point P<0.01 in the total deviation probability plot; cutoff point for GDx was the number >29. Of 174 glaucoma suspect patients, 26 had developed reproducible glaucomatous visual field loss (conversion rate: 3.7% per year). Relative risk was 1.8 (95% confidence interval: 0.9-3.7; P=0.10) for FDT and 2.7 (95% confidence interval: 1.2-6.3; P=0.01) for GDx. Positive predictive value was 0.22 for both FDT and GDx; negative predictive value was 0.88 for FDT and 0.92 for GDx. In a clinical setting, especially GDx may be helpful for identifying glaucoma suspect patients at risk of developing glaucomatous visual field loss as assessed by SAP.