A Strategy for Seeding Point Error Assessment for Retesting (SPEAR) in Perimetry Applied to Normal Subjects, Glaucoma Suspects, and Patients With Glaucoma

Abstract

We sought to determine the impact of seeding point errors (SPEs) as a source of low test reliability in perimetry and to develop a strategy to mitigate this error early in the test.DESIGN: Cross-sectional study. METHODS: Visual field test results from 1 eye of 364 patients (77 normal eyes, 178 glaucoma suspect eyes, and 109 glaucoma eyes) were used to develop models for identifying SPE. Two test cohorts (326 undertaking Swedish interactive thresholding algorithm [SITA]-Faster and 327 glaucoma eyes undertaking SITA-Standard) were used to prospectively evaluate the models for identifying SPEs. Global visual field metrics were compared among reliable and unreliable results. Regression models were used to identify factors distinguishing SPEs from non-SPEs. Models were evaluated using receiver operating characteristic (ROC) curves.RESULTS: In the test cohorts, SITA-Faster produced a higher rate of unreliable visual field results (30%-49.7%) compared with SITA-Standard (10.8%-16.6%). SPEs contributed to most of the unreliable results in SITA-Faster (57.5%-64.9%) compared with gaze tracker deviations accounting for most of the unreliable results in SITA-Standard (40%-77.8%). In SITA-Faster, results with SPEs had worse global indices and more clusters of sensitivity reduction than reliable results. Our best model (using 9 test locations) can identify SPEs with an area under the ROC curve of 0.89.CONCLUSION: SPEs contribute to a large proportion of unreliable visual field test results, particularly when using SITA-Faster. We propose a useful model for identifying SPEs early in the test that can then guide retesting using both SITA algorithms. We provide a simplified framework for the perimetrist to improve the overall fidelity of the test result.

The Frontloading Fields Study (FFS): Detecting Changes in Mean Deviation in Glaucoma Using Multiple Visual Field Tests Per Clinical Visit

“…Visual field testing has several well-known limitations, many of which stem from its dependence upon the patient's ability to reliably perform the test to obtain high-fidelity and accurate results. Factors such as procedural learning, 25 , 26 fatigue, 27 , 28 attention, 12 , 29 , 30 and disease severity 31 play important roles in the variability and repeatability of the sensitivity measurements. As such, intersession and intrasession variance can mask true changes in visual field sensitivity.…”

“…These included a subset of patients who had been previously reported in our previous study (the Frontloading Fields Study). 11 For the purposes of the present study, we included only patients who had reliable results in both tests: <15% false positive rate, no seeding point errors (one or more primary seeding points with artificially reduced sensitivity in the absence of known pathology), and <20% of gaze tracker deviations exceeding 6°, as we have previously defined 11 , 12 . We note that there is debate regarding the use of “traditional” reliability indices, such as recent work demonstrating the low contribution of elevated false positive rates to measurement variability.…”

“…Our variables were progression rate (−0.5, −1, and −2 dB/yr), number of visual field tests per visit (1–4), follow-up intervals (6 months, 1 year, and 2 years), and proportion of reliable visual field results (100% reliable or 0% unreliable, 85% reliable or 15% unreliable, and 70% reliable or 30% unreliable, reflecting a range at which rates of low test reliability may occur in clinical practice using SITA-Faster 8 , 12 , 20 ).…”

“…Aside from the need to recognize slightly greater variability resulting from a faster algorithm, there is also the need to acknowledge the propensity of SITA-Faster to produce a greater rate of results that do not meet current recommendations of reliability, with an almost tripling of this rate compared with SITA-Standard (see below for further discussion). 8 , 12 …”

Ability of 24-2C and 24-2 Grids to Identify Central Visual Field Defects and Structure-Function Concordance in Glaucoma and Suspects

“…The reliability criteria for inclusion in the present study were a false positive rate below 15%; no seeding point errors 28 ; <20% of instances where the gaze tracker deviation exceeded 6 8 during the test; and the absence of other technician-related errors (including incorrect trial lens usage, lens rim artifacts, poor patient position, and others). Elevated rates of false negatives and fixation losses using the Heijl-Krakau method were not used as measurements of low test reliability, as both are poor indicators of true reliability, confounded by the presence of disease and anatomical variation, and because we wished to directly compare the SITA-Standard and SITA-Faster algorithms (in the latter, false negatives and blind spot monitoring were turned off by default).…”