Random Changes of Accommodation Stimuli: An Automated Extension of the Flippers Accommodative Facility Test.

Purpose: To study the accommodative dynamics for predictable and unpredictable stimuli using manual and automated accommodative facility tests Materials and Methods: Seventeen young healthy subjects were tested monocularly in two consecutive sessions, using five different conditions. Two conditions replicated the conventional monocular accommodative facility tests for far and near distances, performed with manually held flippers. The other three conditions were automated and conducted using an electro-optical system and open-field autorefractor. Two of the three automated conditions replicated the predictable manual accommodative facility tests. The last automated condition was a hybrid approach using a novel method whereby far and near-accommodative-facility tests were randomly integrated into a single test of four unpredictable accommodative demands.

Results: The within-subject standard deviations for far- and near-distance-accommodative reversals were (±1,±1) cycles per minute (cpm) for the manual flipper accommodative facility conditions and (±3, ±4) cpm for the automated conditions. The 95% limits of agreement between the manual and the automated conditions for far and near distances were poor: (-18, 12) and (-15, 3). During the hybrid unpredictable condition, the response time and accommodative response parameters were significantly (p < 0.05) larger for accommodation than disaccommodation responses for high accommodative demands only. The response times during the transitions 0.17/2.17 D and 0.50/4.50 D appeared to be indistinguishable between the hybrid unpredictable and the conventional predictable automated tests.

Conclusions: The automated accommodative facility test does not agree with the manual flipper test results. Operator delays in flipping the lens may account for these differences. This novel test, using unpredictable stimuli, provides a more comprehensive examination of accommodative dynamics than conventional manual accommodative facility tests. Unexpectedly, the unpredictability of the stimulus did not to affect accommodation dynamics. Further studies are needed to evaluate the sensitivity of this novel hybrid technique on individuals with accommodative anomalies.