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K. R. Woodward, M. Wall, C. K. Doyle, P. H. Artes; The Relationships Between Threshold Estimates and Effective Dynamic Ranges of Standard Automated Perimetry (Size III and V), Motion and Matrix Perimetry. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1075.
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© ARVO (1962-2015); The Authors (2016-present)
To establish the relationships between threshold estimates of 4 perimetric tests, and to compare the tests’ effective dynamic ranges.
We examined 32 experienced glaucoma patients (median MD -6.7 dB; range -0.1 to -20 dB) and 20 naïve healthy controls five times, once a week for 5 weeks. Participants were examined with: (1) Humphrey Field Analyzer (HFA) SITA Standard stimulus size Goldmann III, (2) HFA Full Threshold Goldmann V, (3) Motion Perimetry (MP), and (4) Matrix perimetry, administered in random order. We explored the relationship between pointwise threshold estimates obtained with the 4 techniques using regression techniques. The lower limit of the effective dynamic range was arbitrarily defined a) as that threshold for which the proportion of retest values with floor effects (thresholds of 0 dB) increased beyond 5%, and b) in which that proportion increased beyond 50%.
In both groups of subjects, the relationship between threshold estimates of all 4 tests was approximately linear over the physiological range of values encountered in controls. However, outside this range the relationships progressively weakened and became difficult to characterize (r-square < 0.1). With SAP III, the proportion of 0-dB estimates (floor effects) increased beyond 5% for thresholds below ~20 dB, and 0-dB estimates were the most frequently encountered retest value for initial estimates below 15 dB. For both definitions of effective dynamic range, the increased stimulus size (V) expanded the range by approximately 5 dB. However, despite their larger stimuli, Matrix and Motion perimetry showed similar floor effects as SAP III.
The effective dynamic range of visual field tests may be chiefly limited by retest variability rather than by the maximum physical intensity of the stimulus. With standard perimetry, the effective dynamic range is substantially narrower than the nominal range of the dB-scale, but larger stimuli (Goldmann V) may reduce the incidence of floor effects and thereby increase the effective range.
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