Glaucoma monitoring in a clinical setting: glaucoma progression analysis vs nonparametric progression analysis in the Groningen Longitudinal Glaucoma Study.

OBJECTIVE: To compare prospectively 2 perimetric progression detection algorithms for glaucoma, the Early Manifest Glaucoma Trial algorithm (glaucoma progression analysis [GPA]) and a nonparametric algorithm applied to the mean deviation (MD) (nonparametric progression analysis [NPA]). METHODS: Patients with a reproducible glaucomatous visual field defect at baseline in at least 1 eye were followed up prospectively using perimetry (Humphrey field analyzer 30-2 Swedish interactive thresholding algorithm). Classifications by GPA and by NPA at the end of the follow-up period were compared. RESULTS: Two hundred twenty-one patients met the inclusion criteria; 1 eye per patient was analyzed. On average, 7.1 reliable fields were available after a mean follow-up period of 5.3 years. The mean MD at baseline was -9.4 dB; the mean MD slope during the follow-up period was -0.25 dB/y. Fifty-six eyes showed progression by GPA and 89 eyes by NPA (P < .001); 42 eyes showed progression by both techniques (kappa = 0.39). In eyes with progression detected by NPA only, baseline MD was worse than that in eyes with progression detected by GPA (-12.5 vs -8.2 dB, P = .002), and GPA more often gave a reading of "baseline MD out of range" (P < .001). After exclusion of eyes with baseline MD out of range, the measure of agreement was kappa = 0.50. CONCLUSIONS: Nonparametric progression analysis had fairly good agreement with GPA. Especially in cases of more advanced disease, NPA labeled more eyes as having progression than GPA.

The Groningen Longitudinal Glaucoma Study. II. A prospective comparison of frequency doubling perimetry, the GDx nerve fibre analyser and standard automated perimetry in glaucoma suspect patients.

PURPOSE: We aimed to determine prospectively the incidence of abnormal test results on frequency doubling perimetry (FDT), the nerve fibre analyser (GDx) and standard automated perimetry (SAP) in a cohort of glaucoma suspect patients with normal findings for all these tests at baseline. METHODS: Seventy glaucoma suspect patients were followed prospectively for 4 years with SAP (Humphrey field analyser 30-2 SITA Fast), FDT (C-20 full-threshold) and GDx (Version 2.010) in a clinical setting. All patients had normal baseline test results on SAP, FDT and GDx. After the follow-up period, the number of patients who converted (whose test results changed from normal at baseline to reproducibly abnormal during follow-up) were counted for each technique and then compared. The cut-off point for FDT was > 1 depressed test-point p < 0.01 in the total deviation probability plot; the cut-off point for GDx was the Number > 29. RESULTS: Of the 70 glaucoma suspect patients, three converted on FDT, 14 on GDx and six on SAP. These proportions are significantly different for GDx versus SAP (p = 0.033) and GDx versus FDT (p = 0.002), but not for FDT versus SAP (p = 0.256). CONCLUSIONS: The most frequent finding after a 4-year follow-up was conversion on GDx.

Influence of test reliability on the screening performance of frequency-doubling perimetry.

PURPOSE: To investigate the influence of test reliability on the screening performance of frequency-doubling perimetry (FDT). DESIGN: Cross-sectional study. METHODS: FDT sensitivity and specificity were calculated three times using three different strategies for handling unreliable (that is, >0 reliability indices outside normal limits) and unfeasible (that is, could not be completed) tests in 452 glaucoma patients from our outpatient department and 237 healthy subjects recruited outside the hospital. RESULTS: Unreliable (P = .01) and unfeasible (P < .001) tests occurred more frequently in glaucoma patients when compared with healthy subjects. Best screening performance was obtained by interpreting unreliable tests as if they were reliable and considering unfeasible tests as positive. With this strategy, sensitivity was 0.90 (95% confidence interval 0.87-0.93) and specificity 0.81 (95% confidence interval 0.76-0.86). CONCLUSIONS: Unreliable and unfeasible FDT tests appear to contain useful information.

The Groningen Longitudinal Glaucoma Study. I. Baseline sensitivity and specificity of the frequency doubling perimeter and the GDx nerve fibre analyser.

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.

Strategies for improving the diagnostic specificity of the frequency doubling perimeter.

PURPOSE: To evaluate various strategies designed to improve the specificity of the interpretation of results obtained with the frequency doubling technology perimeter (FDT) used in the full-threshold mode. METHODS: Three different strategies were compared using data from 452 glaucoma patients and 237 healthy subjects: combining several FDT parameters from a single test, combining the FDT test with a GDx test, and confirming an abnormal FDT test result with a repeat test. RESULTS: Confirming an abnormal FDT test result with a repeat test yielded a specificity increase of 0.10, from 0.80 to 0.90, at the expense of some loss of sensitivity for early but not for moderate or severe glaucoma. Combining several FDT parameters from a single test and combining FDT with GDx did not yield any noticeable increase in diagnostic performance. CONCLUSIONS: A modest increase in FDT diagnostic performance can be obtained by the confirmation of an abnormal test result with a repeat test.

Frequency doubling perimetry screening mode compared to the full-threshold mode.

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.

An evaluation of algorithms designed to classify the results from frequency doubling perimetry.

All previously published algorithms for the interpretation of frequency doubling perimetry test results were compared in full-threshold mode in a large group of glaucoma patients (n = 452) and normal subjects (n = 237). Areas under the receiver-operating characteristic (ROC) curve ranged from 0.86 to 0.92. None of the algorithms performed substantially better than simply counting the number of defects p < 1% in the total deviation plot. For this algorithm, we found a sensitivity of 0.90 and a specificity of 0.81 at a cut-off point of >1 defect, and an area under the ROC curve of 0.92.

Learning effect, normal range, and test-retest variability of Frequency Doubling Perimetry as a function of age, perimetric experience, and the presence or absence of glaucoma.

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).