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CA Hazel, NC Strang; Myopic Accommodation Responses are More Accurate Under 'Real-life' Viewing Conditions . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1504.
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Purpose: Errors in the accommodation response to both open- and closed-loop conditions have been found to be greater in myopes. The complex nature of these errors varies between studies and seems to be dependent on the method of measurement employed. To improve understanding of how accommodation varies between refractive error groups we measure accommodation responses in myopes and emmetropes using 'real-life' and artificial viewing tasks. Methods: 29 young (18-27 years) subjects (19 myopes, 10 emmetropes) participated in the study. All myopic subjects were fully corrected with soft contact lenses. A Shin-Nippon infrared autorefractor was used to measure open-loop accommodation (DF), accommodation stimulus/response gradients (negative lenses) (ASRC), open-loop accommodation adaptation and nearwork induced transient myopia (NITM) using established techniques. Results: The myopes showed reduced accommodation response to negative lenses (lower ASRC gradient, 0-4D) compared to the emmetropes (p<0.05). However, more 'real-life' near target viewing (4D) induced more accurate accommodation responses in the myopic subjects (p<0.05). Under open-loop conditions, myopes showed increased accommodation adaptation (p<0.01) as well as increased variability in the open-loop response (p<0.05) compared to the emmetropes. In contrast, no differences were found in NITM between the myopes and emmetropes (p=0.32). The variability of the steady-state closed-loop accommodation response was similar in both groups (p=0.14). Conclusion: In this study 'real-life' tasks (e.g. those involving near targets and closed-loop conditions) induced a similar level of accommodation response accuracy in myopes and emmetropes. However, more artificial viewing (negative lenses, open-loop conditions) produced less accurate responses in myopes compared to emmetropes. The results highlight the importance of method of measurement used when comparing accommodation responses in different refractive error groups.
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