PURPOSE. Measurement of accommodative amplitude is important in diagnosing accommodative dysfunction and monitoring efficacy of prescribed treatments. Two common clinical tests of accommodation are the push-up method (PU), in free space, and minus-lens method (ML), behind a phoropter. There are few reports in the literature comparing the accuracy and repeatability of these methods. The purpose of this study is to compare the amplitude of accommodation and reproducibility measured by three commonly used techniques METHOD. Twenty subjects (12 male, 8 female) free of ocular or systemic disease and without a history of accommodative or binocular system dysfunction participated in the study. The mean age of the subjects was 25.6 years old. Subjects had their accommodative amplitude measured using the push-up (PU), push-down (PD) or minus lens (ML) method in a random fashion. Breaks were allowed between each measurement method to minimize the effect of previous measurements. All measurements were repeated three times for each visit and again on a subsequent visit separated by at least 24 hours.
RESULTS. The mean amplitudes for the PU, PD and ML were 7.97 D, 8.20 D and 7.46 D respectively. An ANOVA with post-hoc analysis revealed a significant difference (p<0.05) between the means with all of the significant differences occurring between the ML and PU/PD methods. There were no significant differences (p>0.05) between measured amplitudes over the two visits. The 95% CI calculated from mean individual standard deviations for the PU, PD and ML method was ±0.95 D, ±0.84 D and ±0.69 D respectively.
CONCLUSIONS. There is a significant difference in accommodative amplitudes if measured with a phoropter and minus lenses compared to the push-up or push-down techniques in free space. Amplitudes measured behind the phoropter on average will be slightly less than free space techniques, however either method will give repeatable results. Changes in amplitudes of equal to or greater than ±1.00 D, using any of the three techniques, should be considered significant.