|Title:||Accommodative responses in non-Chinese adults, Chinese adults and Chinese children and their association with myopia development in Chinese children|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Myopia -- China
Eye -- Accommodation and refraction -- China
Vision disorders in children -- China
|Department:||Department of Optometry and Radiography|
|Pages:||xv, 286 leaves : ill. (some col.) ; 30 cm|
|Abstract:||Introduction Recent research findings suggested a link between nearwork and the onset, as well as development, of myopia. Extensive investigations on accommodative responses in different refractive groups have been carried out, but it remains unclear whether there are discrepancies in responses between groups. None of these previous studies compared responses in different ethnic groups using the same protocol, by the same examiner, an approach which may be illuminating, given the different prevalence rates for myopia between ethnic groups. In addition, recent technical advances allow the time patterns of accommodative responses, in particular nearwork-induced transient myopia (NITM), to be investigated. Objectives 1. To investigate the amplitude of accommodation, accommodative stimulus-response curve, tonic accommodation and NITM in United Kingdom non-Chinese adults, Hong Kong Chinese adults and Hong Kong Chinese children using the same protocol by the same examiner. 2. To compare these measures in myopic and emmetropic subjects. 3. To study the effect of race by comparing these measures between United Kingdom non-Chinese adults and Hong Kong Chinese adults. 4. To investigate the effect of age by comparing these measures between Hong Kong Chinese adults and children. 5. To determine any changes in these responses in Hong Kong Chinese children as myopia develops over one year. Methods A modified Shin-Nippon SRW-5000 auto-refractor (Shin-Nippon, Japan), an open-field instrument, was used to measure the accommodative responses in static or continuous modes as appropriate. Data collections for non-Chinese adults were carried out in the United Kingdom, while those for Chinese adults and children were carried out in Hong Kong. Results Chinese and non-Chinese adults gave similar amplitude of accommodation, tonic accommodation, accommodative response gradient and NITM results. Chinese adults had a gradient closer to unity and greater tonic accommodation as well as NITM (except NITM in the third 10-seconds post-change after the 5.0 D task), but lower amplitude of accommodation than children. There was no significant change in accommodative amplitude, gradient and NITM in children followed up longitudinally. Chinese myopic children showed an increase in tonic accommodation in the longitudinal study which was not related to their increase in myopia. There was no significant difference in amplitudes of accommodation, tonic accommodation, accommodative response gradient or NITM between myopes and emmetropes. The only difference was a greater accommodative amplitude in child emmetropes than myopes. Conclusions Chinese adults had similar amplitude of accommodation, accommodative response gradient, tonic accommodation and NITM with non-Chinese adults. Current findings indicated that the above accommodative functions were not factors explaining the higher prevalence of myopia found in Chinese. It is not clear if NITM is a factor causing the onset or progression of myopia as both refractive groups demonstrated similar amount of NITM after nearwork and the increase in myopia over time did not have any influence on NITM. The current results are different from previous findings in Chinese children, in which myopes were shown to have significantly greater NITM than emmetropes. The discrepancy in results between the current and previous studies in Chinese children could be due to the different age range of subjects recruited.|
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