Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/21182
Title: Blur detection thresholds in childhood myopia : single and dual target presentation
Authors: Schmid, KL
Iskander, RD
Li, RWH
Edwards, MH
Lew, JKF
Keywords: Aetiology
Blur
Children
Myopia
Near work
Issue Date: 2002
Publisher: Pergamon Press
Source: Vision research, 2002, v. 42, no. 2, p. 239-247 How to cite?
Journal: Vision research 
Abstract: There is some suggestion that the ability to detect blur may be altered in adults with myopia. Here, we address the question of whether children with myopia have worse blur detection than other children, and whether blur detection in myopic children is related to the rate of myopia progression. We recruited 20 myopes and 20 non-myopes aged between 8 and 12 years. Refractive errors, visual acuity, and contrast sensitivity were measured and the change in refractive error over the past year calculated from clinic records. Blur detection thresholds for two different types of black and white targets (text and scenes), two illumination conditions and two testing protocols were determined using a computer-based forced-choice testing procedure. The two testing protocols used were: (i) dual image presentation where subjects were asked to choose the clearer of the two images, one image always having zero blur, and (ii) single image presentation in which the subject reported whether the image was clear or blurred. Blur discrimination ability under all tested conditions was similar for both refractive error groups. Blur detection thresholds were 0.27 ± 0.15 D (myopes) and 0.24 ± 0.07 D (non-myopes) for text images. Thresholds were similar when measured with a one log unit reduction in lighting: 0.27 ± 0.31 D compared to 0.23 ± 0.14 D. Blur detection thresholds were greater for photographic scenes (myopes 0.41 ± 0.36 D, non-myopes 0.44 ± 0.36 D) and when only a single text image (myopes 0.51 ± 0.21 D, non-myopes 0.59 ± 0.01 D) was presented, but this increase was measured in both refractive error groups. There was no correlation between blur thresholds and refractive error magnitude, refractive error progression over the past year, or contrast sensitivity. We found that the blur detection ability showed greater individual variation in myopic children. Further work is required to determine whether blur detection ability is of relevance to myopia development.
URI: http://hdl.handle.net/10397/21182
ISSN: 0042-6989
DOI: 10.1016/S0042-6989(01)00277-2
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