False-response monitoring during automated perimetry.

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.