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Comparing Different Methods of Measuring Accommodative Amplitude with Hofstetter's Normative Values in a Ghanaian
Emmanuel K Abu1, Stephen Ocansey1,2, Joseph Yennu1
1a Department of Optometry, School of Allied Health Sciences , University of Cape Coast , Cape Coast , Ghana.
Aim:
Amplitude of accommodation (AoA) can be determined clinically using different methods. Some methods are known to be more reliable than others for measuring AoA in different age categories. The purpose of this study was to compare Hofstetter's age-expected norms with five recommended methods of measuring AoA in order to determine age-appropriate techniques for a Ghanaian population.
Materials And Methods:
AoA was measured using four subjective methods (push-up, push-down, minus lens, and modified push-up) and one objective method, the modified dynamic retinoscopy. The amplitudes obtained by each technique were compared to each other and also compared to the age-expected amplitudes as predicted by Hofstetter's equations.
Results:
352 non-presbyopes aged 10-39 years were included in this study. All five methods except the push-up (p = 0.089) and modified push-up (p = 0.081) differed significantly from Hofstetter's data, while the modified dynamic retinoscopy recorded the strongest agreement with Hofstetter's average (ICC = 0.78, p ˂ 0.001). With reference to Hofstetter's expected AoA, the minus lens, push-down, modified dynamic retinoscopy, and modified push-up methods underestimated AoA by -4.18D, -1.99D, -0.48D, and -0.43D, respectively. As age increased, underestimated AoA values by the minus lens (10-19 years: -5.57D, 20-29 years: -3.50D, 30-39 years: -2.39D), modified push-up (10-19 years: -1.51D, 20-29 years: +0.40D, 30-39 years: +0.56D), and push-down (10-19 years: -2.90D, 20-29 years: -1.07D, 30-39 years: -1.46D) methods decreased but the modified push-up in relation to Hofstetter's expected was most accurate for the older age. The push-up, on the other hand, overestimated accommodation in all age categories by +0.42D (10-19 years: +0.01D, 20-29 years: +0.82D, 30-39 years: 0.67D). Thus, the push-up method became more accurate as age decreased.
Conclusion:
This study suggested that Hofstetter's formulae could be used to predict the amplitudes of Ghanaian non-presbyopes aged 10-39 years using the push-up and modified push-up. With regard to Hofstetter's data, the push-up method was more accurate for the younger age-group 10-19 years while the modified push-up was more accurate for the older age-group 20-39.