Introduction: Common clinical methods of evaluating the accommodative response are the Monocular Estimation Method (MEM) and Nott Retinoscopy. While these tests are typically performed at 40 cm, MEM may also be performed at Harmon’s distance or the habitual reading distance. Few studies have compared the consistency of the accommodative response with varying working distance for these methods.
Purpose: This study investigated if i) the accommodative response varies as a function of working distance, ii) response measurements are comparable for MEM and Nott methods at different working distances.
Methods: Subjects (N=56), ages 20-30 years, with best corrected visual acuities of 20/25 or better were recruited. Dynamic retinoscopy was performed on the right eye at 50, 40, and 25 cm working distances using MEM and Nott retinoscopy, starting at 50 cm and moving inward. Short periods of rest were given between stations to allow for relaxation of accommodation.
Results: Average lag measurements for each method at 50, 40, and 25 cm were MEM: +0.48 ± 0.46 D, +0.43 ± 0.49 D, +0.26 ± 0.47 D, respectively, Nott: +0.36 ± 0.44 D, +0.37 ± 0.39 D, +0.33 ± 0.33 D, respectively. Mean lag data for the three distances were analyzed using a one-way Analysis of Variance (ANOVA). The results were statistically significant for MEM, [F(2, 163) = 3.34, p < 0.037], and non-significant for Nott [F(2, 163) = 0.14, p < 0.87]. A two-way ANOVA run to compare response data at different distances between the MEM and Nott methods was statistically non-significant (F(2,2) = 2.77, p < 0.064).
Conclusions: Preliminary results suggest that the accommodative response varies significantly with working distance for the MEM but not for the Nott method. There was no significant difference in response measurements between the two methods. These results may have clinical implications, when determining the most optimal method for measuring the accommodative response.