title: Visual search with image modification in age-related macular degeneration.
abstract: OBJECTIVE
  AMD results in loss of central vision and a dependence on low-resolution peripheral vision. While many image enhancement techniques have been proposed, there is a lack of quantitative comparison of the effectiveness of enhancement. We developed a natural visual search task that uses patients' eye movements as a quantitative and functional measure of the efficacy of image modification.
  
  
  METHODS
  Eye movements of 17 patients (mean age = 77 years) with AMD were recorded while they searched for target objects in natural images. Eight different image modification methods were implemented and included manipulations of local image or edge contrast, color, and crowding. In a subsequent task, patients ranked their preference of the image modifications.
  
  
  RESULTS
  Within individual participants, there was no significant difference in search duration or accuracy across eight different image manipulations. When data were collapsed across all image modifications, a multivariate model identified six significant predictors for normalized search duration including scotoma size and acuity, as well as interactions among scotoma size, age, acuity, and contrast (P < 0.05). Additionally, an analysis of image statistics showed no correlation with search performance across all image modifications. Rank ordering of enhancement methods based on participants' preference revealed a trend that participants preferred the least modified images (P < 0.05).
  
  
  CONCLUSIONS
  There was no quantitative effect of image modification on search performance. A better understanding of low- and high-level components of visual search in natural scenes is necessary to improve future attempts at image enhancement for low vision patients. Different search tasks may require alternative image modifications to improve patient functioning and performance.
authors.affiliation: Massachusetts Eye and Ear Infirmary, 20 Staniford Street, Boston, MA 02118, USA. emily.wiecek@schepens.harvard.edu
authors.forename: Emily
authors.initials: E
authors.lastname: Wiecek
authors.forename: Mary Lou
authors.initials: ML
authors.lastname: Jackson
authors.forename: Steven C
authors.initials: SC
authors.lastname: Dakin
authors.forename: Peter
authors.initials: P
authors.lastname: Bex
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity / Q000502:physiology; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008268:Macular Degeneration / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012607:Scotoma / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology