Carrie K. Doyle

Repeatability of automated perimetry: a comparison between standard automated perimetry with stimulus size III and V, matrix, and motion perimetry.

PURPOSE Standard automated perimetry (SAP) shows a marked increase in variability in damaged areas of the visual field. This study was conducted to test the hypothesis that larger stimuli are associated with more uniform variability, by investigating the retest variability of four perimetry tests: standard automated perimetry size III (SAP III), with the SITA standard strategy; SAP size V (SAP V), with the full-threshold strategy; Matrix (FDT II), and Motion perimetry. METHODS One eye each of 120 patients with glaucoma was examined on the same day with these four perimetric tests and retested 1 to 8 weeks later. The decibel scales were adjusted to make the tests scales numerically similar. Retest variability was examined by establishing the distributions of retest threshold estimates, for each threshold level observed at the first test. The 5th and 95th percentiles of the retest distribution were used as point-wise limits of retest variability. Regression analyses were performed to quantify the relationship between visual field sensitivity and variability. RESULTS With SAP III, the retest variability increased substantially with reducing sensitivity. Corresponding increases with SAP V, Matrix, and Motion perimetry were considerably smaller or absent. With SAP III, sensitivity explained 22% of the retest variability (r(2)), whereas corresponding data for SAP V, Matrix, and Motion perimetry were 12%, 2%, and 2%, respectively. CONCLUSIONS Variability of Matrix and Motion perimetry does not increase as substantially as that of SAP III in damaged areas of the visual field. Increased sampling with the larger stimuli of these techniques is the likely explanation for this finding. These properties may make these stimuli excellent candidates for early detection of visual field progression.

The repeatability of mean defect with size III and size V standard automated perimetry.

PURPOSE The mean defect (MD) of the visual field is a global statistical index used to monitor overall visual field change over time. Our goal was to investigate the relationship of MD and its variability for two clinically used strategies (Swedish Interactive Threshold Algorithm [SITA] standard size III and full threshold size V) in glaucoma patients and controls. METHODS We tested one eye, at random, for 46 glaucoma patients and 28 ocularly healthy subjects with Humphrey program 24-2 SITA standard for size III and full threshold for size V each five times over a 5-week period. The standard deviation of MD was regressed against the MD for the five repeated tests, and quantile regression was used to show the relationship of variability and MD. A Wilcoxon test was used to compare the standard deviations of the two testing methods following quantile regression. RESULTS Both types of regression analysis showed increasing variability with increasing visual field damage. Quantile regression showed modestly smaller MD confidence limits. There was a 15% decrease in SD with size V in glaucoma patients (P = 0.10) and a 12% decrease in ocularly healthy subjects (P = 0.08). CONCLUSIONS The repeatability of size V MD appears to be slightly better than size III SITA testing. When using MD to determine visual field progression, a change of 1.5 to 4 decibels (dB) is needed to be outside the normal 95% confidence limits, depending on the size of the stimulus and the amount of visual field damage.

Size Threshold Perimetry Performs as Well as Conventional Automated Perimetry With Stimulus Sizes III, V, and VI for Glaucomatous Loss

PURPOSE It is thought that large perimetric stimuli are insensitive for demonstrating visual field defects. To test the hypothesis that there is no difference in the total number of abnormal test locations with total deviation empiric probability plots in glaucoma patients, we compared results of glaucoma patients tested with sizes III (0.43° diameter), V (1.72°), and VI (3.44°), and size threshold perimetry (STP), a method that finds threshold by changing stimulus size. METHODS We derived normative limits for total deviation probability plots using the second test from 60 age-matched normals. We analyzed the probability plots of 120 glaucoma patients (mean deviation was -9.3 ± 6.1 dB with a range of -0.2 to -31.6) at the 42 nonblind spot locations common to the tests. We compared the number of abnormal test locations at the 5% level among the tests using one-way repeated measures ANOVA on ranks. We stratified the results by mean deviation. RESULTS There was a statistically significant difference in the number of abnormal test locations among the tests: III, 28.5; V, 29.7; VI, 27.0; and STP, 28.8, P = 0.001; Tukey pairwise comparisons were statistically significant for the assessments between sizes V and VI and between STP and size VI. When stratifying by mean deviation, with mild visual loss, size V was most sensitive, followed by STP; size VI appeared slightly less sensitive. CONCLUSIONS Size V and STP provide favorable stimulus methodology for detection of mild to moderate glaucoma. Size VI appears slightly less sensitive for glaucoma with mild loss.

Refinement of Pointwise Linear Regression Criteria for Determining Glaucoma Progression

PURPOSE A variety of pointwise linear regression (PLR) criteria have been proposed for determining glaucomatous visual field progression. However, alternative PLR criteria have only been assessed on a limited basis. The purpose of this study was to evaluate a range of PLR slope and significance criteria to define a clinically useful progression decision rule for longitudinal visual field examinations. METHODS Visual field data for each of 140 eyes (one per participant among 96 cases and 44 controls) were evaluated using the Humphrey Field Analyzer II program 24-2 Swedish interactive thresholding algorithm standard test strategy and Goldmann size III stimuli. The pointwise linear regression A2 (PLRA2) method was used to analyze the data, which included nine visual field examinations performed every 6 months for 4 years. Data from the Ocular Hypertension Treatment Study (OHTS) were used to validate the decision rule. RESULTS Several slope criteria produced specificities of 0.90 or higher, particularly slope criteria of less than -1.2 dB/y. The use of the slope criterion less than -1.2 dB/y at a significance level of P < 0.04 for classification resulted in a hit rate of 0.38, more than a 2-fold increase compared with a commonly used standard slope criterion of less than -1.0 dB/y at a significance level of P < 0.01. A similar increase in the hit rate was shown for a slope of less than -1.2 dB/y and P < 0.04 compared with the standard criterion in the independent OHTS validation data. CONCLUSIONS When systematically evaluating criteria for detecting glaucoma progression, PLR criteria can be refined by requiring a stricter slope criterion such as less than -1.2 dB/y and relaxing the significance criterion to P < 0.04. Increasing the hit rate of PLR will be useful for early detection and treatment of glaucoma.

A comparison of false-negative responses for full threshold and SITA standard perimetry in glaucoma patients and normal observers.

Purpose:To compare false-negative (FN) rates for Full Threshold (FULL) and Swedish Interactive Threshold Algorithm (SITA) Standard automated perimetry in healthy control subjects and glaucoma patients. Methods:One eye of 19 glaucoma patients and 5 normal control subjects underwent 5 visual field examinations within 6 weeks on the Humphrey Field Analyzer II using the 24-2 FULL and SITA testing procedures. The order of presentation of test procedures was counterbalanced across participants. We obtained FN response procedures that presented stimuli 9 dB greater than a previously determined threshold value at specific locations in the visual field (FULL) or up to 20 dB greater than the threshold value (SITA), and evaluated whether the patient responded to these suprathreshold stimuli. We compared the percentage of FN responses for the FULL and SITA tests before (Peridata output) and after postprocessing of data. Results:The percentage of FNs was almost twice as high for FULL testing compared with the 2 SITA analyses. The SD of FN percentages was half as large for SITA postprocessing compared with FULL and SITA Peridata procedures. Because the distributions were not normally distributed, a Kruskal-Wallis analysis of variance was performed and revealed a statistically significant difference (H=13.094, P<0.001) for FN percentages among the 3 evaluations. Conclusions:FULL test procedures yield about twice as many FNs as SITA procedures. This may be related to the SITA method of testing for FN in relatively normal areas as opposed to any location (even if it has low sensitivity) with FULL. Because FN responses can be due to either high variability in damaged areas or pathologic variations, these revised FN procedures provide greater assistance in properly interpreting visual field results.

Variability of rarebit and standard perimetry sizes I and III in normals.

Purpose. To compare test-retest variability in rarebit perimetry (RBP) and conventional standard automated perimetry (SAP) using Goldmann size I and III stimuli. Methods. Seventeen normal subjects underwent RBP, size I SAP, and size III SAP on five separate visits within a 5-week period. Test-retest variability could not be directly compared because of differences in units. Instead, data were transformed to lie on the same scale by calculating a percentile range to mean ratio for each test. Results. Percentile range to mean ratio was highest for size I (3.42 ± 0.62), followed by size III (2.29 ± 0.55), and RBP (0.29 ± 0.10). Results for all three tests were significantly different from each other. Conclusions. Comparison of tests with different scales is problematic, but RBPs retest variability appears to be significantly less than both sizes I and III SAP in the measurement of normal subjects.

Total Deviation Probability Plots for Stimulus Size V Perimetry: A Comparison With Size III Stimuli

OBJECTIVE To compare empirical probability plots in patients with glaucoma for size V and III perimetry testing. METHODS We computed empirical probability plot percentile limits after testing 60 age-matched controls tested with both size III (Swedish interactive thresholding algorithm) and size V (full threshold) perimetry twice. Probability plots of 120 patients with glaucoma tested in the same way were computed. We compared the number of abnormal test locations in the 2 stimulus sizes; we then compared these results with those from size III StatPac software (Zeiss Humphrey Systems, Dublin, California) using 2-way repeated-measures analysis of variance. RESULTS We found a similar number of abnormal test locations (P < or = .05) for the size III and size V testing conditions identified by the probability plots (no significant difference); there were significantly fewer abnormal locations using StatPac (size III) than from our size III database. When results were stratified by mean deviation, the mild visual loss group again did not show any significant differences between sizes III and V. CONCLUSIONS Size V full-threshold testing gives a similar number of abnormal test locations in patients with glaucoma compared with the size III Swedish interactive thresholding algorithm standard test. Size V testing, with its greater dynamic range and lower variability, may be a viable alternative to size III testing in patients with glaucoma.

A comparison of catch trial methods used in standard automated perimetry in glaucoma patients.

PurposeTo compare the false-positive (FP) response rates between 2 methods used by the Humphrey Field Analyzer in glaucoma patients. MethodsOne eye of one hundred and twenty glaucoma patients was tested twice within 2 months with 24-2 SITA Standard and 24-2 full threshold (FT) perimetric test procedures. FP rates were obtained with the response time window (RTW) method used by SITA and the blank presentation (BP) method of the size V FT procedure. False-negative (FN) catch trial rates were also examined. A repeated measure, 2×2 analysis of variance was used to examine error rates, and FP rates for visits 1 and 2 were regressed to investigate its relationship. ResultsFor FP rates on the first 2 visits, glaucoma patients had no significant differences comparing RTW (SITA) with BP (FT) (1.99% vs. 1.88%) and higher mean FN rates (4.11% vs. 1.69%, P=0.001); the FP rates at visit 2 were similar (1.69% vs. 2.08%) and FN rates were lower for both methods at visit 2. However, when comparing patients with FP responses that occurred with both RTW and BP methods, RTW rates were lower (3.58% vs. 7.72%, P=0.007). ConclusionsThe RTW method seems to underestimate FP response rates.