ABSTRACT.Purpose: To describe the baseline data of a large cohort of patients included for follow-up with perimetry using the frequency doubling technique (FDT) and with quantification of the retinal nerve fibre layer as assessed by GDx, and to calculate the sensitivity and specificity of both devices from these baseline data. Methods: Regular visitors to our glaucoma service were included. All subjects were followed for at least 4 years with FDT in full-threshold mode, GDx and conventional perimetry. Patients were classified as having either glaucoma or suspect glaucoma, according to baseline perimetry results. In addition, a group of healthy subjects was recruited outside the hospital. Results: A total of 452 glaucoma patients, 423 glaucoma suspects and 237 healthy subjects were incorporated into the analyses. Sensitivities for both FDT and GDx were fixed at 0.90. For the group as a whole, the specificity was 0.81 for FDT, using number of depressed test-points p < 0.01 in the total deviation probability plot with a cut-off point > 1, and 0.78 for GDx, using the Number, with a cut-off point > 29. The area under the receiver operating characteristic (ROC) curve was 0.92 for FDT and 0.94 for GDx. Of the subjects with suspect glaucoma, 75% showed normal FDT test results and 52% showed normal GDx results. Unlike FDT, GDx failed to detect some moderate/severe glaucoma cases. Conclusions: The performances of FDT and GDx are approximately equivalent in terms of sensitivity, specificity and area under the ROC curve. In glaucoma suspects, GDx in particular yielded a rather high percentage of positive test results. The majority of these positive test results are presumably false-positive results rather than results indicating preperimetric glaucoma.

The diagnostic performance of the frequency doubling perimetry (FDT) C20-1 screening mode was compared to that of the C20 full-threshold mode. For the number of defects p < 1% in the total deviation plot, both modes appeared to perform similarly in terms of sensitivity, specificity, and area under the receiver-operating characteristic (ROC) curve. Different cut-off points should be applied for both modes to obtain equal sensitivity and specificity values, and - related to that - for most subjects more defects were found in full-threshold mode than in screening mode. For the screening mode, we found a sensitivity of 0.91 and a specificity of 0.88 at a cut-off point of >0 defects, and an area under the ROC curve of 0.93.

Purpose To investigate whether frequencydoubling perimetry (FDT) and nerve fibre analyser (GDx) test results are able to predict glaucomatous visual field loss in glaucoma suspect patients. Methods 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 41 depressed test point Po0.01 in the total deviation probability plot; cutoff point for GDx was the number 429. Results 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 ¼ 0.10) for FDT and 2.7 (95% confidence interval: 1.2-6.3; P ¼ 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. Conclusions 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.

The learning effect for several different Frequency Doubling Perimetry parameters was studied in full threshold mode in a large group of patients (n = 342) of various ages, with and without perimetric experience, and with and without glaucoma. A significant learning effect was only found for the mean deviation (MD) in aged normals without perimetric experience. The median of MD increased for both OD (from +0.2 to +1.0 dB) and for OS (from +0.5 to +1.3 dB). The effect disappeared largely during a third visit (median OD +1.2 dB, OS +1.3 dB). The normal range and the test-retest variability were measured in the same dataset. The learning effect for MD (1 dB or less) appeared to be small as compared with both the normal range (about 12 dB) and the test-retest variability (about 3 dB).