July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Trail Traced Threshold Test (T4) algorithm shows reduced variability compared to the Swedish Interactive Thresholding Algorithm (SITA)
Author Affiliations & Notes
  • Bledi Petriti
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • Marco A Miranda
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • Haogang Zhu
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
    Division of Optometry and Visual Sciences, City University London, London, United Kingdom
  • Padraig Mulholland
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
    Optometry and Vision Science Research Group, University of Ulster, Coleraine, United Kingdom
  • David Crabb
    Division of Optometry and Visual Sciences, City University London, London, United Kingdom
  • Carol Bronze
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • Roger Anderson
    Optometry and Vision Science Research Group, University of Ulster, Coleraine, United Kingdom
  • David F Garway-Heath
    National Institute for Health Research (NIHR) Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
  • Footnotes
    Commercial Relationships   Bledi Petriti, None; Marco Miranda, University College London (P); Haogang Zhu, City University (P); Padraig Mulholland, Heidelberg Engineering (R); David Crabb, Allergan (R), ANSWERS (P), CenterVue (C), Roche (F), Santer (R); Carol Bronze, None; Roger Anderson, None; David Garway-Heath, ANSWERS (P), CenterVue (C), Moorfields MDT (P), T4 (P)
  • Footnotes
    Support  NIHR Invention for Innovation Award (PI David Garway-Heath)
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 5115. doi:
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      Bledi Petriti, Marco A Miranda, Haogang Zhu, Padraig Mulholland, David Crabb, Carol Bronze, Roger Anderson, David F Garway-Heath; Trail Traced Threshold Test (T4) algorithm shows reduced variability compared to the Swedish Interactive Thresholding Algorithm (SITA). Invest. Ophthalmol. Vis. Sci. 2018;59(9):5115.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To compare the test-retest variability of a novel threshold algorithm (T4sm) for automated perimetry compared to SITA-Standard.

Methods : We have developed a VF algorithm (T4sm) with two novel components: stimuli are modulated primarily in size (sm) rather than intensity and thresholds are determined by an algorithm (T4), which derives a probability function obtained from patient’s responses to all stimuli presented at the location of interest and anatomically related locations. Stimulus dynamic range and step units were matched between algorithms. Study eye inclusion criteria: glaucomatous VFs, BCVA ≧20/40, no ocular morbidity other than glaucoma or prior cataract surgery, reliable VF (false positive <15%), IOP <30mmHg. Subjects performed T4sm and SITA VFs twice in the same order on two runs. Test sequence and test eye were block randomized. Analysis focused on the standard deviation (SD) of the pointwise test-retest difference of each strategy. Bland-Altman repeatability plots were created for each.

Results : Results of the first 40 out of 100 subjects. SITA MD -6.18dB (SD 7.26; 5% -21.50dB, 95% 0.96dB). Mean age 67 (SD 11) years. Mean test time: SITA 5.40 (SD 1.07) mins, T4sm 5.16 (SD 0.53) mins. Mean absolute test retest differences for sensitivity values ≥26dB for SITA and T4sm were 1.41 and 1.63dB respectively, and for values <26dB, 5.63 and 2.95dB respectively. Fig. 1 plots the SD of test retest difference against the mean sensitivity for every location. Results from SITA are in good agreement with previous estimates (Russell et al. 2012). Bland-Altman plots (Fig. 2) showed the 95% test retest limits of agreement to be ±13.4dB for SITA (mean difference 0.2dB) and ±11.5dB for T4sm (mean difference 0.5dB). The heteroscedasticity of test-retest variability is markedly reduced with T4 compared to SITA.

Conclusions : Interim results show T4sm has almost 50% lower variability than SITA at sensitivies <26dB, and importantly, reduced heteroscedasticity, so that the test-retest variability is much more even across the sensitivity range. The lower variability at lower-sensitivity increases precision to identify progression in patients with established glaucoma.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure 1. The SD of absolute differences between test and retest sensitivity at various sensitivity levels

Figure 1. The SD of absolute differences between test and retest sensitivity at various sensitivity levels

 

Figure 2. Bland-Altman plot of differences between test and retest vs their mean for SITA and T4sm

Figure 2. Bland-Altman plot of differences between test and retest vs their mean for SITA and T4sm

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