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.
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).
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.
Our results suggest that using a small artificial pupil to open the accommodation loop may not produce a veridicial measure of open-loop accommodation.
- Tonic accommodation
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