The measurement of adaptation of tonic accommodation under two open-loop conditions

Pre- and post-task tonic accommodation (TA) was measured using an objective infra-red optometer under two open-loop conditions: a darkroom and a bright empty-field (60 cd m-2). The task was of 10 minutes' duration and was located at -1, -3 and -5 D. Post-task TA was measured immediately after the task and over a period of 90 s. Mean data for the group of 10 young men subjects showed that the open-loop condition adopted had no significant influence on the post-task regression patterns of TA towards pre-task values. Three subjects did, however, show significantly more sustained increases in post-task TA for the bright-field condition; one markedly so. Conversely, two subjects showed more pronounced post-task shifts for the darkroom condition.