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Use of a Continuous Probability Scale to Display Visual Field Damage
Michael Wall, MD;
Chris A. Johnson, PhD;
Randy H. Kardon, MD, PhD;
David P. Crabb, PhD
Arch Ophthalmol. 2009;127(6):749-756.
Objective To derive and display the percentile score (1st-99th percentile) at each perimetric location of a standard automated perimetry test to determine whether this technique will uncover patterns of loss not visible in standard (StatPac) probability maps.
Methods We computed continuous scale probability plots of data collected from testing 305 visually healthy participants with standard automated perimetry (24-2 Swedish interactive thresholding algorithm). The age-corrected thresholds were sorted by sensitivity at each visual field location. Percentiles were derived in single increments from the 1st to the 99th. We displayed the percentiles as a color scale and then interpreted visual field plots from healthy control subjects and patients with visual system disorders.
Results Added information was achieved for identifying patterns of visual loss by using the 5th- to 20th-percentile range in conjunction with the lower range below the 5th percentile that is typically used. The extent of contiguous regional defects appeared larger using this method. Healthy control subjects often have threshold results within the 5th- to 20th-percentile range, but these test locations usually appeared randomly spaced rather than in contiguous patterns commonly seen in patients at the border of visual field defects.
Conclusion Continuous scale probability plots are a potentially useful adjunct for interpretation of perimetry results.
Author Affiliations: Departments of Neurology (Dr Wall) and Ophthalmology (Drs Wall, Johnson, and Kardon), University of Iowa College of Medicine, Veterans Administration Hospital, Iowa City; and Department of Optometry and Visual Science, City University, London, England (Dr Crabb).
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