The magnitude and distribution of open-loop accommodation using three different methods of opening the loop

Purpose. The present study examines the magnitude, distribution, and relationship of open-loop accommodation obtained using the three most common methods of opening the accommodation loop. Methods. Open-loop accommodation was measured in 93 young, emmetropic subjects using a Canon R1 objective infrared optometer, and the accommodation loop was opened using the following methods: (1) dark empty field (DA), (2) bright empty field (BA), and (3) viewing a target through a small artificial pupil (PA), Results. PA was found to elicit significantly (p = 0.0001) higher values of open-loop accommodation than either DA or BA and demonstrated a much wider distribution of values than DA or BA, A further experiment demonstrated that the higher PA was attributable to the proximal effect of placing a small artificial pupil close to the eye. Conclusions, Our results suggest that using a small artificial pupil to open the accommodation loop may not produce a veridical measure of open-loop accommodation.