Comparing Autorefractors for Measurement of Accommodation

Purpose To compare the static and dynamic accommodative responses measured with the WAM-5500 and the PowerRef-II autorefractors. Methods The dynamic and static monocular accommodative responses were measured with the WAM-5500 and the PowerRef-II instruments in 30 pre-presbyopic patients (23.66 [3.19] years). The spherical equivalent was measured at 0.00, 2.50, and 5.00 diopters (D) of accommodative stimulation for the static measurements. The subjective refraction was also determined. Dynamic accommodation was measured for abrupt changes of stimulus vergence of 2.00 D. Mean and peak velocities of accommodation and disaccommodation were evaluated. For the PowerRef-II, dynamic measurements were calculated for sampling frequencies of 5 and 25 Hz. Results For far distance static results, the differences between subjective and WAM-5500 measurements were 0.07 (+/- 0.21) D (p = 0.093) and those between subjective and PowerRef-II measurements were 0.70 (+/- 0.47) D (p = 0.001). The difference in the response measured with both instruments was 0.08 (+/- 0.32) D (p = 0.194) for 2.50 D and -0.32 (+/- 0.48) D (p = 0.001) for 5.00 D of stimulation. For the dynamic mode, the PowerRef-II at 25 Hz measured faster mean and peak velocities of accommodation and disaccommodation than the WAM-5500, with statistically significant (p < 0.05) differences of 0.68 (+/- 1.01), 0.67 (+/- 0.98), 1.26 (+/- 1.19), and 1.42 (+/- 1.53) D/s, respectively. With a sampling frequency of 5 Hz for the PowerRef-II, these differences, which were statistically significant (p < 0.05), were reduced to 0.52 (+/- 0.90), 0.49 (+/- 0.91), 0.83 (+/- 1.07), and 0.83 (+/- 1.31) D/s, respectively. Conclusions There is good agreement between subjective refraction and WAM-5500 measurements. In contrast, the PowerRef-II produced more hyperopic results. There were no differences among instruments at 2.50 D of static stimulation; however, differences were found at 5.00 D. In the dynamic measurements, the PowerRef-II measured faster velocities, partly attributed to the difference in the sampling frequency.