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False-response monitoring during automated perimetry
1Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia. a.vingrys@optometry.unimelb.edu.au
Purpose:
To ascertain the accuracy and precision of the catch-trial monitor used to estimate the false-response rate in automated perimetry.
Methods:
False responses were automatically injected at various rates by modified perimetric software while reliable perimetric subjects underwent visual field thresholding. Four repeat tests were conducted within a 1-hour period to quantify the variability and bias inherent in the catch-trial technique.
Results:
The catch-trial method gave a very accurate estimate of the average false-response rate. Precision, however, was quite poor because of the small sample of catch trials. Outcomes were predicted using a binomial model, and we demonstrated good concordance between the model and empirical data. When the true false-response rate was 33%, estimates derived from catch trials ranged from 7 to 57%.
Conclusions:
Although the catch-trial method gave an accurate estimate of the false-response rate, confidence intervals were too wide to provide a high level of precision. Our data suggest that tests with reported false-response rates < 20% may be considered reliable.