A New SITA Perimetric Threshold Testing Algorithm: Construction and a Multicenter Clinical Study

Abstract

To describe a new time-saving threshold visual field-testing strategy-Swedish Interactive Thresholding Algorithm (SITA) Faster, which is intended to replace SITA Fast-and to report on a clinical evaluation of this new strategy. DESIGN: Description and validity analysis for modifications applied to SITA Fast. METHODS: Five centers tested 1 eye of each of 126 glaucoma and glaucoma suspect patients with SITA Faster, SITA Fast, and SITA Standard at each of 2 visits. Outcomes included test time, mean deviation, and the visual field index (VFI), significant test points in probability maps, and intertest threshold variability. RESULTS: Mean (standard deviation) test times were 171.9 (45.3) seconds for SITA Faster, 247.0 (56.7) for SITA Fast, and 369.5 (64.5) for SITA Standard (P < .001). SITA Faster test times averaged 30.4 % shorter than SITA Fast and 53.5 % shorter than SITA Standard. Mean deviation was similar among all 3 tests.VFI did not differ between SITA Fast and SITA Faster tests, mean difference 0%, but VFI values were 1.2% lower with SITA Standard compared to both SITA Fast (P [ .007) and SITA Faster (P [ .002). A similar trend was seen with a slightly higher number of significant test points with SITA Standard than with SITA Fast and SITA Faster. All 3 tests had similar test-retest variability over the entire range of threshold values. CONCLUSIONS: SITA Faster saved considerable test time. SITA Faster and SITA Fast gave almost identical results. There were small differences between SITA Faster and SITA Standard, of the same character as previously shown for SITA Fast vs SITA Standard. (Am J

Clinical Evaluation of Swedish Interactive Thresholding Algorithm–Faster Compared With Swedish Interactive Thresholding Algorithm–Standard in Normal Subjects, Glaucoma Suspects, and Patients With Glaucoma

“…Patients formed 3 diagnostic categories, the first 2 of which were similar to the criteria presented by Heijl and associates. 34 First, patients with glaucoma were diagnosed as per current glaucoma guidelines, 35,36 including clear characteristic glaucomatous structural anomalies at the optic nerve head (including, but not limited to: increased cup-to-disc ratio, cup-to-disc asymmetry, and neuroretinal rim thinning or notching) and/or retinal nerve fiber layer (corresponding to the aforementioned neuroretinal rim changes), with or without corresponding visual field loss and with or without elevated intraocular pressure. Second, glaucoma suspects included those being followed on the basis of clinical features suspicious for but not conclusive for glaucoma, including elevated intraocular pressure (defined as >21 mm Hg on applanation tonometry), suspicious optic disc or retinal nerve fiber layer changes, significant systemic, ocular, or family risk factors for glaucoma, or suspicious visual field results.…”

“…The perimetrist administered the test (unmasked to the algorithm) as per the instructions presented on the screen by the instrument before test commencement, as per the methods of Heijl and associates. 34 The perimetrist monitored the patient carefully throughout the test, with proper head, eye, and lens positioning maintained to avoid lens rim artifacts. If during the test there were signs of unreliability, such as gaze instability, high false positive rates, inattentiveness, or others, the perimetrist was permitted to stop the test, to reiterate the instructions to the patients, and to restart once.…”

“…Numerous modifications to SS and SITA-Fast leading to SFR have enabled this reduction in test time, including eliminating stimulus presentation delay and modifications to the starting stimulus intensity and staircase reversals to arrive at the sensitivity threshold at the primary ''seeding'' points (the 4 points at the 9 8 :9 8 position in each quadrant that provide an initial estimate of sensitivity in adjacent test locations). In a comparison of the 3 SITA paradigms, Heijl and associates 34 demonstrated that SITA-Fast and SFR produced almost identical results in terms of sensitivity and probability scores, and small differences between SFR and SS. The logic was therefore extended to potentially replacing SS with SFR in order to meet an increasing demand of more perimetric tests in clinical practice.…”

“…One recent suggestion has been the use of SITA-Faster (SFR), 34 an updated version of the SITA family of threshold-estimating paradigms, that has been shown to reduce testing time by approximately 50% compared with SS. Numerous modifications to SS and SITA-Fast leading to SFR have enabled this reduction in test time, including eliminating stimulus presentation delay and modifications to the starting stimulus intensity and staircase reversals to arrive at the sensitivity threshold at the primary ''seeding'' points (the 4 points at the 9 8 :9 8 position in each quadrant that provide an initial estimate of sensitivity in adjacent test locations).…”

“…The goal of the present study was to compare the use of SS and SFR to address 3 practical questions related to their clinical use, adding to the work already presented by Heijl and associates. 34 First, we determined the number of unreliable visual field test results and the reasons for their occurrence, and then related these back to the modifications of SFR. These results were used to address the second aim, which was to determine whether SFR results in an overall saving of clinical testing time, after factoring in retesting of unreliable results.…”