Abstract
Background: Historically, two clinical methods have been used for measuring the amplitude
of accommodation, which are the push-up and minus lens methods. However, it has been
documented that the push-up method overestimates amplitude of accommodation, while the
minus lens method underestimates it.
Aim: The purpose of this study was to compare subjective and objective procedures for
determining the monocular amplitude of accommodation in young optometry students.
Setting: The study was conducted in the optometry clinic at the university.
Methods: Amplitude of accommodation was measured on 45 optometry students (17 males
and 28 females, whose ages ranged from 21 to 27 years) using the push-up, push-down, minus
lens, modified dynamic retinoscopy and Pascal dynamic retinoscopy methods. Data were
collected by three different examiners in this study. One examiner measured all the subjective
tests, while another examiner measured the modified dynamic retinoscopy. The third examiner
measured the Pascal heterodynamic retinoscopy.
Results: The highest amplitude of accommodation was obtained using the push-up method
(10.23 ± 1.67 D), while the minus lens method gave the lowest subjective finding (8.43 ± 1.68 D).
However, the subjective methods generally produced comparable results. Both retinoscopic
methods showed the lowest mean amplitude of accommodation of approximately 6.50 ± 1.40 D.
However, there was a high correlation between the various methods.
Conclusion: The push-up and push-down methods overestimate the true amplitude of
accommodation because of the relative magnification, while the minus lens method creates
an abnormal viewing environment in which the target is stationary but the stimulus becomes
increasingly minified. Subjective amplitude of accommodation is an inadequate measure
to assess any true accommodation because it fails to differentiate between passive depth
of focus and an active accommodative power change in the eye. Therefore, subjective
measurement of the amplitude of accommodation may suggest that accommodation is
present when it is not. Further research is needed to further validate dynamic retinoscopy
as the optimal or best possible routine clinical method to assess the true amplitude of
accommodation.