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Luke Xiang-Yu Chong, Paul H Artes, Michael Wall, Thomas Callan, Vincent Michael Patella, Gary C Lee, Matthias Monhart, John G Flanagan; Perimetric Threshold Predictability Between Goldmann Size III and V Stimuli. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2842.
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© ARVO (1962-2015); The Authors (2016-present)
Prior studies have demonstrated that a size V stimulus extends the clinically useful dynamic range of visual field testing, and has better repeatability. The aim of this study was to establish whether it is feasible to switch from size III to V whilst continuing to accurately monitor glaucomatous progression. We determined the conversion factors for perimetric sensitivity from Goldmann stimulus sizes III and V in order to assess their predictability.
Ninety-six patients with early glaucoma (mean deviation -4.0 dB or better) and 118 healthy patients were examined using the Full Threshold 24-2 strategy with sizes III and V, as well as the SITA Standard 24-2 procedure (SS). We compared results after applying a uniform global correction across the whole field versus a correction based on eccentricity. Scatter plots and Bland-Altman plots were generated to assess predictability between procedures.
There was no clinically significant difference between applying a global correction and a correction based on eccentricity. There was no significant difference in the Bland-Altman limits of agreement when comparing III predicting III, SS predicting III, and III predicting V in both the healthy (Figure 1; III predicting III = 9.8 dB; SS predicting III = 9.5 dB; III predicting V = 10.2 dB) and early glaucoma (Figure 2; III predicting III = 12.8 dB; SS predicting III = 12.7 dB; III predicting V = 13.4 dB) groups. The limits of agreement for SS predicting V were 1 dB tighter than III predicting V in the healthy group (SS predicting V = 9.2 dB; III predicting V = 10.2 dB), and 1.6 dB tighter in the early glaucoma group (SS predicting V = 11.8 dB; III predicting V = 13.4 dB).
Applying a global correction to convert between stimuli is suitable, as using a correction by eccentricity does not provide any increase in accuracy or precision of threshold estimates when converting between size III and V stimuli. Our results showed that III predicting V is no worse than III predicting III, and therefore suggest that it is feasible to switch from size III to V without sacrificing accuracy.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1: Scatter (left column) and Bland-Altman (right column) plots of the healthy group with global correction.
Figure 2: Scatter (left column) and Bland-Altman (right column) plots of the early glaucoma group with global correction.
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