The working threshold approach to Friedmann visual field analyser screening.

Central visual field screening of 2223 eyes without field defects was conducted with the Friedmann Visual Field Analyser Mark II. There was wide variation in the filter setting at which all stimuli were seen and in the working threshold relative to the recommended age filter. The ability to see all stimuli at settings higher than the age filter was found in 803 eyes (36.1%). The difference between mean working threshold and the age filter ranged from 0.22 to 0.40 log units, being greatest in middle age groups. The performance of the screener in correctly identifying normal eyes was thus improved with the working threshold approach, as the criterion for depression of sensitivity was an individually determined threshold.