Effect of instructions on conventional automated perimetry

PURPOSE. To investigate the effect of perimetrists' instructions on automat ed perimetry thresholds. METHODS. Eighteen volunteers in two age groups participated in a series of three test sessions. Each session consisted of a Humphrey Field Analyzer 30 -2 test, a questionnaire, and a customized test program using a Humphrey pe rimeter to construct frequency of seeing (FOS) curves from which thresholds were calculated, and a descriptive measure of response criterion was deriv ed. The FOS curves were obtained at a central and a peripheral test locatio n within the same test session. The three test sessions differed only by th e instructions given. The instructions were adapted from those listed in th e manufacturer's instruction manual and were designed to influence particip ants to respond to the stimuli in a conservative, Liberal, or neutral manne r. RESULTS. For the 30-2 threshold test, a significant difference in mean devi ation was found among the three instruction types (P = 0.001) and between t he two age groups (P = 0.001). Although differences were small in the young er subjects (2.04 dB), the means for the responses from liberal to conserva tive differed by 6.57 dB in the older subjects. Thresholds obtained in a pe ripheral location by the customized threshold test were found to differ sig nificantly between the age groups (younger group mean, 31.0 dB; older group mean, 27.2 dB) and among the instruction types (liberal mean, 30.9 dB; con servative mean, 28.1 dB; and neutral mean, 30.3 dB; P < 0.001). The descrip tive measurement of response criterion suggests that a difference in criter ia occurred as a result of the instructions in both peripheral and central locations for both age groups (P = 0.0001). In addition, according to self- reports, liberal instructions caused participants to be more likely to resp ond, whereas the conservative instructions caused them to be more reluctant to respond. CONCLUSIONS. Perimetrists' instructions can significantly affect obtained a utomated perimetry thresholds.