Expert Evaluation of Visual Field Decay in Glaucoma Correlates With the Fast Component of Visual Field Loss.

PURPOSE: To compare the assessment of serial visual fields (VFs) based on subjective expert evaluation with the fast and slow VF component rates determined with pointwise exponential regression (PER) and pointwise linear regression (PLR). MATERIALS AND METHODS: A total of 5272 VF examinations from 376 eyes diagnosed with open-angle glaucoma were included. Three glaucoma specialists assessed each VF qualitatively to evaluate progression status and the qualitative rate of progression. The rates of VF decay were determined with PER and PLR at each VF location, which were ranked according to the regression coefficient and partitioned into 2 groups (fast and slow). A mean rate for the fast and slow partitions was obtained based on the average of the regression coefficients in each partition. κ-values were used to measure the agreement among the experts and the PER and PLR algorithms. RESULTS: The average baseline VF mean deviation for the study sample was -6.6 (±5.9) dB. The agreement of the likelihood of progression among the dichotomized experts' score and PER was moderate (κ=0.41, P<0.01) and fair (κ=0.39, P<0.01) for PLR. The agreement of the likelihood of progression among the 3 dichotomized experts' scores was fair (κ=0.22, P<0.01). The agreement of the area of worsening among the dichotomized experts' score and PER and PLR were both moderate (κ=0.48, P<0.01; κ=0.46, P<0.01). The eyes flagged by experts as having "fast" progression rates had a higher average rates of decay for PER and PLR at -2.7 (±4.1) %/year and -0.8 (±1.2) dB/year; eyes flagged as "slow" had lower rates of decay at -0.3 (±1.5) %/year and -0.1 (±0.5) dB/year. CONCLUSIONS: Expert qualitative evaluation of field series for change and rate of change correlate more closely with the fast component than with the slow component of VF decay.

Influence of the disc-fovea angle on limits of RNFL variability and glaucoma discrimination.

PURPOSE: To determine factors affecting the disc-fovea angle (DFA), and to test the hypotheses that adjusting for DFA improves limits of retinal nerve fiber layer (RNFL) variability in normal subjects or enhances performance of RNFL measures for glaucoma detection. METHODS: Disc-fovea angle was measured on scanning laser ophthalmoscope fundus images from 170 eyes (110 normal and glaucoma subjects). The DFA measurements were repeated in 24 eyes. The relationship between DFA and various anatomic variables was explored. Main outcome measures were changes in 95% RNFL prediction limits or glaucoma discrimination after adjusting for DFA. We also explored the angle between temporal raphe and horizontal meridian in 19 eyes with nasal field defects limited to one hemifield. RESULTS: Average mean deviation and DFA were -0.1 (±1.2) dB and -6.6° (±3.4°) and -4.1 (±3.3) dB and -7.9° (±3.9°) in the control and glaucoma groups, respectively (P < 0.001 and = 0.029). The average difference between DFA repeat measurements was 2.0° (±1.8°). Predictors for DFA were female sex (P = 0.004), smaller disc area (P = 0.006), and glaucoma diagnosis (P = 0.019). The absolute change in sectoral RNFL thickness was 6.1 (±3.9) and 4.6 (±3.1) µm in control and glaucoma subjects, respectively. Retinal nerve fiber layer prediction limits improved in 5, 9, and 10 o'clock sectors (P < 0.02). Discrimination ability for the best-performing RNFL sector did not improve (P = 0.936). The average angle between temporal raphe and horizontal meridian was 0.8° (±0.8°). CONCLUSIONS: Disc-fovea angle measurements demonstrated fair intersession repeatability. While adjusting for DFA improved RNFL prediction limits in some sectors, it did not enhance glaucoma detection.

Influence of correction of ocular magnification on spectral-domain OCT retinal nerve fiber layer measurement variability and performance.

PURPOSE: To analyze the influence of ocular magnification on the peripapillary retinal nerve fiber layer (RNFL) thickness measurement and its performance as acquired with spectral-domain optical coherence tomography (SD-OCT). METHODS: Spectral domain OCT measurements from 108 normal eyes (59 subjects) and 72 glaucoma eyes (58 patients) were exported and custom software was used to correct RNFL measurements for ocular magnification. Retinal nerve fiber layer prediction limits in normal subjects, structure-function relationships, and RNFL performance for detection of glaucoma were compared before and after correction for ocular magnification (Bennett's formula). Association of disc area with cross-sectional RNFL area was explored. RESULTS: The median (interquartile range, [IQR]) visual field mean deviation and scaling factor were 0 (-0.85 to 0.73) dB and 0.96 (0.93-1.00) in normal eyes and -4.0 (-6.0 to -2.2) dB and 0.99 (0.95-1.03) in the glaucoma group (P < 0.001 and P = 0.003, respectively; average correction 3%). Correction for ocular magnification caused a reversal of the negative relationship between the cross-sectional RNFL area and axial length (slope = -0.022 mm(2)/mm, P = 0.015 vs. = 0.22 mm(2)/mm, P = 0.007). However, such correction did not change RNFL prediction limits (except in superior and nasal quadrants), improve global or regional structure-function relationships, or enhance the ability of RNFL measurements to discriminate glaucoma from normal eyes (P > 0.05). The cross-sectional RNFL area was not correlated with optic disc area (P = 0.325). CONCLUSIONS: Correction of RNFL measurements for ocular magnification did not improve prediction limits in normal subjects or enhance the performance of SD-OCT in this group of eyes in which the axial length did not deviate significantly from average values. The cross-sectional area of the RNFL was not related to the optic disc area.

Performance of the visual field index in glaucoma patients with moderately advanced visual field loss.

PURPOSE: To explore the relationship between the visual field index (VFI) and the visual field mean deviation (MD) in glaucoma patients with moderately advanced perimetric damage and to identify the magnitude of the boundary effect of VFI that occurred when the VFI estimation strategy changed from pattern deviation probability value to total deviation probability value as the MD crossed -20 dB in longitudinal visual field (VF) series. DESIGN: A retrospective cohort study of longitudinal data analysis. METHODS: The MD and VFI values obtained from VF tests conducted on 148 eyes of 148 glaucoma patients having an MD around -20 dB were studied. A total of 1286 VFs with MD values within the range of -16 dB to -24 dB were included. The eyes were divided into 2 groups, with the first having serial MDs all better than or all worse than -20 dB and the second with serial MDs crossing the -20 dB value. Change in MD (ΔMD) was defined as the absolute difference between the MD values of 2 consecutive VFs. Based on the 2 VFI values of the same VFs, the absolute value of change in VFI (ΔVFI) was calculated. RESULTS: The means (± standard deviation) for the ΔVFI were 4.17% (± 3.3%) in the group of eyes with MDs on either side of -20 dB, and were 15.8% (± 8.4%) in the group with MDs crossing -20 dB (P < .0001). For ΔVFI/ΔMD, these values were 6.8%/dB (± 10.5%) when the range of MD falls on either side of -20 dB, and 7.9%/dB (± 6.2%) when the range of MD crosses the -20 dB values (P = .042). CONCLUSIONS: The values of the VFI become highly variable in serial VFs of eyes with MDs crossing -20 dB, in comparison to those VFIs associated with MDs on either side of -20 dB. The likelihood for this effect is the change from use of pattern deviation probability value to total deviation probability value in the points included in the calculation of VFI at -20 dB of MD. The development of indices to measure VF rates that are free from this boundary effect in moderately advanced glaucoma is desirable.

Macular ganglion cell/inner plexiform layer measurements by spectral domain optical coherence tomography for detection of early glaucoma and comparison to retinal nerve fiber layer measurements.

PURPOSE: To evaluate the performance of ganglion cell layer/inner plexiform layer (GCL/IPL) measurements with spectral-domain optical coherence tomography (Cirrus HD-OCT) for detection of early glaucoma and to compare results to retinal nerve fiber layer (RNFL) measurements. DESIGN: Cross-sectional prospective diagnostic study. METHODS: We enrolled 99 subjects, including 59 eyes with glaucoma (47 subjects) (mean deviation >-6.0 dB) and 91 normal eyes (52 subjects). Patients underwent biometry and peripapillary and macular OCT imaging. Performance of the GCL/IPL and RNFL algorithms was evaluated with area under receiver operating characteristic curves (AUC), likelihood ratios, and sensitivities/specificities adjusting for covariates. Combination of best parameters was explored. RESULTS: Average (SD) mean deviation in the glaucoma group was -2.5 (1.9) dB. On multivariate analyses, age (P < 0.001) and axial length (P = 0.03) predicted GC/IPL measurements in normal subjects. No significant correlation was found between average or regional GC/IPL thickness and respective outer retina (OR) thickness measurements (P > 0.05). Average RNFL thickness performed better than average GCL/IPL measurements for detection of glaucoma (AUC = 0.964 vs 0.937; P = 0.04). The best regional measures from each algorithm (inferior quadrant RNFL vs minimum GCL/IPL) had comparable performances (P = 0.78). Entering the GC/IPL to OR ratio into prediction models did not enhance the performance of the GCL/IPL measures. Combining the best parameters from each algorithm improved detection of glaucoma (P = 0.04). CONCLUSIONS: Regional GCL/IPL measures derived from Cirrus HD-OCT performed as well as regional RNFL outcomes for detection of early glaucoma. Using the GC/IPL to OR ratio did not enhance the performance of GCL/IPL parameters. Combining the best measures from the 2 algorithms improved detection of glaucoma.