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Emily K. Wiecek, Mary Lou Jackson, Steven Dakin, Peter J. Bex; Visual Search with Image Enhancements in Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4392.
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Age-related macular degeneration (AMD) results in loss of central vision and a dependence on low-resolution peripheral vision. Many image enhancement techniques have been proposed; however, while there is qualitative evidence that AMD patients prefer some methods, there is a lack of quantitative measurement of the effectiveness of alternative enhancement methods. We developed a natural visual search task with eye movement recording as a quantitative and objective measure of image enhancement.
Sixteen patients with AMD were required to locate audio-prompted targets in natural images. Eight different image enhancement methods were implemented in total of 80 images and included manipulations of local image or edge contrast, color and crowding. Eye positions were recorded with a 1000 Hz remote eye tracker. In a subsequent task, patients also ranked their preference of the image enhancements.
There was no significant difference in search duration or accuracy across the eight different image enhancement methods within individual subjects. Patient age, as well as acuity and scotoma size in the better eye were positively correlated with both search duration and error across all enhancements (p<0.05). There was no significant interaction between age, performance, and enhancement method. In the ranking task, subjects preferred the original images in the majority of cases (p <0.05), although this was not associated with a significant improvement in search time or accuracy.
Image enhancement methods may be a useful tool in improving function in patients with AMD; however, it is difficult to quantify with objective methods the effect of enhancement on performance. There was no significant difference in performance error and search duration for any of eight candidate image enhancements in patients with central vision loss. Ultimately, patients preferred the original natural images suggesting that the peripheral visual field is optimized for the distribution of spatial structure in natural scenes.
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