Fatigue effects in automated perimetry

Abstract

The influence of fatigue and related factors on automated perimetric testing was evaluated in both eyes of sixteen normal observers and sixteen patients with early-to-moderate visual field loss using a Digilab 750 automated perimeter and a customized test procedure. False positive rate, false negative rate, and detection sensitivity at 5, 10, 15, and 20° eccentricity were measured in 1.5-min intervals throughout a 21-min visual field examination. Half of the normal observers and patients with visual field loss were given a brief rest (1.5-min) midway through each visual field exam to determine whether this would reduce fatigue effects. Our findings revealed that patients displayed considerably higher average false positive and false negative rates than normal observers. However, neither the patients nor normal observers demonstrated any consistent changes in false positive rate or false negative rate as a function of testing duration. In contrast, both normal observers and patients showed an average decrease in sensitivity as a function of increasing test duration with the magnitude of the time-dependent sensitivity loss becoming greater with increasing stimulus eccentricity. Patients demonstrated a larger time-dependent sensitivity loss than normal observers, averaging ~4dB at 20° eccentricity. The introduction of a brief pause midway through the test procedure appeared to reduce the time-dependent sensitivity loss for the second half of the test procedure, especially for greater eccentricities.