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PremNandhini Satgunam, Cyril Sara Babukutty; Can vision impaired children perform visual search tasks?. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4154.
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Visual search experiments (feature and conjunction search) have indicated younger children to have poorer performance in comparison to adults because of attention deployment. However, visual search can be used as a marker for visual performance. Such a marker can help objectively evaluate the effectiveness of image enhancement technology as a potential rehabilitation tool, as shown in adults. We asked the questions could vision impaired (VI) children perform visual search task (in real world scenes)? How does their performance compare to normally sighted (NS) children?
VI (binocular acuity worse than 20/60) children (n=12, mean age±SD:11±3.4) and NS (monocular acuities better than 20/30) children (n=8, mean age:10±4) were enrolled with parents informed consent. 150 images with real-world scenes (half randomly enhanced) were presented on a computer monitor. A search target was displayed at the top left corner of the monitor along with the image. Children were asked to point to this target within the image as quickly and accurately as possible. The examiner clicked the mouse in the pointed direction. The images were divided into 3 categories: Face, Indoor and Collections. Accuracy and search time were measured and was used in computing the overall visual performance.
All the children were able to complete all the 150 trials. Face images were harder to search in both groups. Assumptions for parametric test was satisfied, hence 2 sample t-test was used. Search time (VI: 7s±1.7 (mean±SD) and NS: 4.5s±1.2) and accuracy (VI:77.5% and NS:92.5%) were significantly different between the groups whether the images were enhanced or not (p≤0.01). The overall visual performance accounting for speed and accuracy together was significantly different between NS and VI for both enhanced (p=0.04) and unenhanced (p=0.01) images. About 75% of VI children had better performance with image enhancement.
We have shown that search task (real-world scenes) is possible in children as young as 5 years and even with VI. Interestingly, VI children tended to show an improvement in performance with enhanced images. This finding opens up some exciting possibilities for rehabilitation in VI children.
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