Frontloading SITA-Faster Can Increase Frequency and Reliability of Visual Field Testing at Minimal Time Cost

Multiple (frontloaded) visual field tests increase identification of very slow mean deviation progression in glaucoma

OBJECTIVE

To determine the effect of frontloading (multiple) visual field (VF) tests at the same visit for detecting mean deviation (MD) change in slowly progressive glaucoma.

METHODS

This was a computer simulation study. Baseline MD (range, 0 to -12 dB) and progression rate (range, 0 to -0.4 dB/year, non-inclusive) were generated for 10,000 patients. Each patient had 6 simulated "stable" baseline VF tests. Then follow-up VFs (up to 10 years) were generated by incorporating progression rate and within-visit and between-visit variability. The independent variables were number of VF tests per visit (one non-frontloaded or two frontloaded), VF reliability (100%, 85%, or 70%), repeat testing because of unreliable results (yes or no), and follow-up interval (6-monthly or yearly). The outcomes were detection of progression (MD slope that was negative and significant at p < 0.05), MD at detection, and number of years to detection.

RESULTS

Frontloading identified more progressors (62.7%-79.2%) compared with non-frontloading (31.0%-36.7%) at 10 years (p < 0.0001). Six-monthly follow-ups led to greater detection than yearly intervals. Progressors detected by both methods were detected by the non-frontloaded method sooner (up to 0.26 years), but this was small and not clinically significant (MD difference, 0.06 dB). An increase (less severe) in MD, an increase (slower) in progression rate, and an increase in SD of baseline VFs decreased the likelihood of detecting progression.

CONCLUSIONS

Frontloading VF tests at 6-monthly intervals improve detection rates of MD progression in slowly progressive glaucoma patients compared with performing 1 test per visit at yearly intervals.

Visual field testing in glaucoma using the Swedish Interactive Threshold Algorithm

The Swedish Interactive Thresholding Algorithm (SITA) is the main measurement acquisition algorithm used on the Humphrey Field Analyser, the most commonly used instrument for visual field (VF) assessment worldwide. We compare the sensitivity outputs and reliability parameters of the three currently available SITA algorithms-SITA Standard (SS), Fast (SF), and Faster (SFR), with a focus on the newly released SFR and the 24-2C test grid. SFR displays similar sensitivity outputs to SS and SF, but may not be interchangeable with SS in eyes with more severe VF loss. The reliability metric with the greatest impact on VF reliability is the level of false positives, although the recommended 15% false positive cut off may be inappropriate as a threshold for judging whether a test is reliable and should be included for use in SFR. Finally, the 24-2C grid may be useful in flagging the presence of a clustered central VF defect, while the 10-2 grid can be used to more comprehensively characterize central field defects. We also discuss strategies to improve testing frequency in clinical practice.

A Practical Framework for the Integration of Structural Data Into Perimetric Examinations

Purpose

We sought to develop and evaluate a practical framework that supports structurally enhanced perimetric examinations.

Methods

Two perimetric strategies were compared: standard Zippy Estimation through Sequential Testing (ZEST) procedure, a traditional visual field test with population-based prior distributions, and structural-ZEST (S-ZEST), enhanced with individual optical coherence tomography data to determine the starting parameters. The integration and collection of data was facilitated by a bespoke application developed in Shiny R (R Studio). The test was implemented using the Open Perimetry Interface on the Compass perimeter (CentreVue-iCare, Italy). The strategies were evaluated via simulations and on 10 visually healthy participants. The usability of the application was assessed in a simulated environment with 10 test users.

Results

In simulations, the S-ZEST improved test speed in patients with glaucoma. In the practical implementation, there was a statistically significant decrease in the testing time (approximately 26%) and in the number of presentations per test with S-ZEST (P < 0.001). The structure-function relationship was similar between the two strategies. The time taken for users to complete the sequence of actions on the application was 52.9 ± 11.5 seconds (mean ± standard deviation).

Conclusions

Structurally enhanced perimetric examination can significantly improve test time in healthy subjects and can be delivered through a user-friendly interface. Further testing will need to assess feasibility and performance of S-ZEST in patients with glaucoma.

Translational Relevance

We have developed a user-friendly web application based within the Shiny environment for R, which implements an automated extraction of optical coherence tomography data from raw files and performs real-time calculations of structural features to inform the perimetric strategy.

Quantification and Predictors of Visual Field Variability in Healthy, Glaucoma Suspect, and Glaucomatous Eyes Using SITA-Faster

PURPOSE

The newly released Swedish Interactive Thresholding Algorithm (SITA)-Faster (SFR) has significantly shorter testing durations compared with older SITA algorithms, but its variability is uncertain. This study quantified and established threshold limits of test-retest variability across the 24-2 test grid using SFR.

DESIGN

Cross-sectional study with prospective longitudinal arm.

PARTICIPANTS

1426 eyes of 787 patients with healthy, suspected glaucoma, or manifest glaucoma eyes from hospital- and university- eye clinics.

METHODS

Two SFR tests per eye at a baseline visit and at two follow-up visits.

MAIN OUTCOME MEASURES

Pointwise variability measured by test-retest difference in pointwise sensitivity between tests one and two, mean global variability (test-retest variance) measured by average of pointwise variability for each participant, global sensitivity, and reliability indices of each eye.

RESULTS

Of the 1426 eyes, 540 eyes (37.9%) had a diagnosis of glaucoma, 753 eyes (52.8%) were suspected of having glaucoma, and the remaining 133 eyes (9.3%) were healthy. Of 74 152 pointwise sensitivities obtained, the mean test-retest difference was 2.17 ± 2.9 dB, whereas the mean test-retest variance for each participant was 2.17 ± 1.2 dB. Pointwise and global variability increased with worsening threshold sensitivity and (MD), respectively, and was greater for peripheral compared with central test locations. In the longitudinal cohort, no significant difference in mean test-retest variance was found across the 3 visits (mean variability, 2.10 dB vs. 2.16 dB vs. 2.16 dB at visits F0 vs. F1 vs. F2; P = 0.53, repeated-measures analysis of variance). Baseline MD (-0.19 dB; 95% CI, -0.22 to 0.16 dB; P < 0.0001) and abnormally high sensitivity on glaucoma hemifield test (1.14 dB; 95% CI, 0.78-1.51 dB; P < 0.0001) were significantly associated with increased variability. Finally, test-retest MD showed minimal change around the recommended 15% false-positive cutoff threshold.

CONCLUSIONS

The variability of SFR increases with worsening threshold sensitivity, is stable over time, and is greater for peripheral compared with central test locations. Worse baseline MD and abnormally high sensitivity are significant predictors of increased variability. A cutoff of 15% in false-positive results may be inappropriate as a threshold for judging test reliability in SFR.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Frontloading visual field tests detect earlier mean deviation progression when applied to real-world-derived early-stage glaucoma data

PURPOSE

To examine the diagnostic accuracy of performing two (frontloaded) versus one (clinical standard) visual field (VF) test per visit for detecting the progression of early glaucoma in data derived from clinical populations.

METHODS

A computer simulation model was used to follow the VFs of 10,000 glaucoma patients (derived from two cohorts: Heijl et al., Swedish cohort; and Chauhan et al., Canadian Glaucoma Study [CGS]) over a 10-year period to identify patients whose mean deviation (MD) progression was detected. Core data (baseline MD and progression rates) were extracted from two studies in clinical cohorts of glaucoma, which were modulated using SITA-Faster variability characteristics from previous work. Additional variables included follow-up intervals (six-monthly or yearly) and rates of perimetric data loss for any reason (0%, 15% and 30%). The main outcome measures were the proportions of progressors detected.

RESULTS

When the Swedish cohort was reviewed six-monthly, the frontloaded strategy detected more progressors compared to the non-frontloaded method up to years 8, 9 and 10 of follow-up for 0%, 15% and 30% data loss conditions. The time required to detect 50% of cases was 1.0-1.5 years less for frontloading compared to non-frontloading. At 4 years, frontloading increased detection by 26.7%, 28.7% and 32.4% for 0%, 15% and 30% data loss conditions, respectively. Where both techniques detected progression, frontloading detected progressors earlier compared to the non-frontloaded strategy (78.5%-81.5% and by 1.0-1.3 years when reviewed six-monthly; 81%-82.9% and by 1.2-2.1 years when reviewed yearly). Accordingly, these patients had less severe MD scores (six-monthly review: 0.63-1.67 dB 'saved'; yearly review: 1.10-2.87 dB). The differences increased with higher rates of data loss. Similar tendencies were noted when applied to the CGS cohort.

CONCLUSIONS

Frontloaded VFs applied to clinical distributions of MD and progression led to earlier detection of early glaucoma progression.

Evaluation of the Consistency of Glaucomatous Visual Field Defects Using a Clustered SITA-Faster Protocol

PURPOSE

Frontloading SITA-Faster (SFR) visual fields (2 tests per eye on the same visit) has been shown to provide repeatable perimetric data at minimal time cost. This study reports the outcomes of using frontloaded SFR in the evaluation of pointwise visual field (VF) defects in a cohort of patients with glaucoma when transitioned from SITA-Standard (SS).

DESIGN

Prospective, cross-sectional study.

PARTICIPANTS

A total of 144 eyes of 91 patients with confirmed or suspected glaucoma who had an SS test on a previous visit.

METHODS

Two SFR tests (T1, T2) per eye on the same visit.

MAIN OUTCOME MEASURES

Global sensitivity, reliability indices, and pointwise deviation map probability scores from the pattern deviation grid of each patient were compared across the 3 sequential tests to evaluate the consistency of VF defects.

RESULTS

The mean age was 68.6 years, and 79.2% of patients had a diagnosis of glaucoma. There was no significant difference in mean deviation (MD) across the 3 tests (-5.83 decibels [dB], -5.28 dB, and -5.71 dB in SS, SFR1, and SFR2, respectively, repeated-measures analysis of variance [ANOVA], P = 0.48). The frontloaded SFR tests provided repeatable VFs that confirmed existing pointwise data on the SS in 4661 (62.3%) locations, reversed an SS defect in 614 (8.2%) locations, and demonstrated a new repeatable defect in 406 (5.4%) locations of the pattern deviation grid. A new defect of at least 3 contiguous points was identified in 20.1% of eyes. The non-repeatable points on the 2 SFR tests displayed no significant difference in the distribution of defect/nondefect points based on test order or peripheral versus central locations. There was no significant difference in the rate of obtaining at least 1 reliable test result between SS and the frontloaded SFR T1 and T2 (P = 0.77). Test duration significantly decreased from SS to SFR1/2 (379 vs. 160 vs. 158 seconds, P < 0.0001).

CONCLUSIONS

Frontloading SFR tests can provide repeatable data for the evaluation of the consistency of pattern deviation defects in glaucoma, with no observable decline in performance from test fatigue. This is achieved at equivalent duration and reliability as a single SS test. Frontloading SFR may be helpful in increasing testing frequency/quantity to meet recommended guidelines for progression analysis.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.