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Effects of Contour Enhancement on Low-Vision Preference and Visual Search

Satgunam, PremNandhini*; Woods, Russell L.; Luo, Gang; Bronstad, P. Matthew; Reynolds, Zachary§; Ramachandra, Chaithanya; Mel, Bartlett W.; Peli, Eli

doi: 10.1097/OPX.0b013e318266f92f
Original Articles

Purpose. To determine whether image enhancement improves visual search performance and whether enhanced images were also preferred by subjects with vision impairment.

Methods. Subjects (n = 24) with vision impairment (vision: 20/52 to 20/240) completed visual search and preference tasks for 150 static images that were enhanced to increase object contours' visual saliency. Subjects were divided into two groups and were shown three enhancement levels. Original and Medium enhancements were shown to both groups. High enhancement was shown to group 1, and Low enhancement was shown to group 2. For search, subjects pointed to an object that matched a search target displayed at the top left of the screen. An “integrated search performance” measure (area under the curve of cumulative correct response rate over search time) quantified performance. For preference, subjects indicated the preferred side when viewing the same image with different enhancement levels on side-by-side high-definition televisions.

Results. Contour enhancement did not improve performance in the visual search task. Group 1 subjects significantly (p < 0.001) rejected the High enhancement, and showed no preference for Medium enhancement over the Original images. Group 2 subjects significantly preferred (p < 0.001) both the Medium and the Low enhancement levels over Original. Contrast sensitivity was correlated with both preference and performance; subjects with worse contrast sensitivity performed worse in the search task (ρ = 0.77, p < 0.001) and preferred more enhancement (ρ = −0.47, p = 0.02). No correlation between visual search performance and enhancement preference was found. However, a small group of subjects (n = 6) in a narrow range of mid-contrast sensitivity performed better with the enhancement, and most (n = 5) also preferred the enhancement.

Conclusions. Preferences for image enhancement can be dissociated from search performance in people with vision impairment. Further investigations are needed to study the relationships between preference and performance for a narrow range of mid-contrast sensitivity where a beneficial effect of enhancement may exist.

*BS(Opt), MS, PhD

MCOptom, PhD, FAAO

PhD

§BA

MS

MSc, OD, FAAO

Schepens Eye Research Institute, Massachusetts Eye and Ear, and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts (PS, RLW, GL, PMB, ZR, EP), Department of Biomedical Engineering (CR, BWM), and Neuroscience Graduate Program (BWM), University of Southern California, Los Angeles, California.

Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.optvissci.com).

Received January 17, 2012; accepted May 4, 2012.

Eli Peli Schepens Eye Research Institute 20 Staniford St Boston, MA 02114-2500 e-mail: eli.peli@schepens.harvard.edu

© 2012 American Academy of Optometry