• Vol. 35 No. 12, 868–874
  • 15 December 2006

Accommodative Stimulus Response Curve of Emmetropes and Myopes



Introduction: Myopes are suspected to be poorer at responding to accommodative stimuli than emmetropes, and this may worsen the degree of their myopia. The study aims to compare the abilities of young adult emmetropes and myopes in responding to accommodative stimuli, as indicated by their Accommodation Stimulus Response Curves (ASRCs) in a predominantly Chinese population.

Materials and Methods: Seventeen emmetropes and 33 myopes aged between 16 and 23 years (mean, 18.6 ± 1.2) were recruited, of whom 11 were progressing and 22 were non-progressing myopes. The ASRC gradients of subjects were measured using the methods of decreasing distance series (DDS), positive (PLS) and negative lens series (NLS).

Results: The ASRC is method dependent. The gradients of the curves are significantly different among 3 methods of measurement using single-factor ANOVA (F3.057 = 44.815, P<0.01). The slopes of the accommodative errors of all subjects were steeper using the NLS method, and the lags of accommodation increased with elevated demands. No significant differences in ASRC gradients were found between emmetropes, non-progressing myopes and progressing myopes for the range of accommodative demands for each method. Progressing myopes showed the highest error towards the higher demand compared with the emmetropes and non-progressing myopes.

Conclusion: Accommodative responses of myopes were more sluggish though there were no statistical differences in ASRC gradients between emmetropes and myopes. It is not certain if the poorer accommodative responses were a cause, or a consequence, of myopia.

There is a strong association between myopia and near work, and it has been reported that the rapid rise in the prevalence of myopia in Singaporean children may be related to an increase in near work demands such as reading. Although the mechanism by which near work affects myopia progression is not known, prolonged chronic accommodation during close work has been implicated in myopia.

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