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.
Highlights
Accommodation can be defined as an increase in the refractive or dioptric power of the crystalline lens of the eye that enables the image of near objects of regard to be focused on the retina.[1,2,3,4,5,6,7,8]
Rosenfield and Gilmartin[24] mentioned that the pushup method gives a higher value of the amplitude of accommodation because as the target distance decreases there is an increase in the angular size of the retinal image and there is an increase in the proximal stimulation to the accommodation
Depth of focus is the extent to which the image may be positioned in front or behind the retina but still appear to be clear,[24,25] whereas depth of field is the range of the object distances over which http://www.avehjournal.org there is no detectable change in visual acuity or the visual acuity does not deteriorate.[24,25,26]
Summary
Accommodation can be defined as an increase in the refractive or dioptric power of the crystalline lens of the eye that enables the image of near objects of regard to be focused on the retina.[1,2,3,4,5,6,7,8] accommodation can be defined as the eye’s mechanism by which it adjusts its power to focus on objects at different distances.[4]. 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
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