A comparison in university students of the amplitude of accommodation determined subjectively

Abstract

Background: Historically, the push-up and the minus lens methods have been used for the measurements of the amplitude of accommodation, and the differences between the results of these methods are well known.

Aim: The purpose of this study was to compare three methods for determining the monocular amplitude of accommodation and consider whether agreement exists between such methods.

Setting: The study was conducted at the Optometry Clinic, University of Limpopo.

Method: Thirty-four (N = 34) African optometry students participated in this study. There were 20 female and 14 male students. The age range of the participants was 20–34 years. Amplitude of accommodation was measured via the subjective push-up, push-down and minus lens methods only on the right eyes of the sample.

Results: The highest average amplitude of accommodation was obtained with the push-up method (10.20 D ± 0.96 D), while the minus lens method produced the smallest mean amplitude of accommodation (9.66 D ± 0.75 D). A higher correlation was found between the push-up and push-down methods (r = 0.80, p = 0.06). The smallest correlation was observed between the push-up and the minus lens methods (r = 0.60, p = 0.062). There were no statistically significant differences between the amplitude of accommodation in male and female students for all three methods (p > 0.005).

Conclusion: It seems easier to recognise the point where one can identify a target in pushdown amplitude than the point of first sustained blur in the push-up method. The push-up method tends to overestimate the actual amplitude of accommodation because of the effects of depth of focus. The less evaluated method in the literature is the push-away method; however, further research is necessary to answer the question of which (if any) method is more accurate.