Critical orientation for face identification in central vision loss.

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Difficulty identifying faces is a common complaint of people with central vision loss. Dakin and Watt (2009) reported that the horizontal components of face images are most informative for face identification in normal vision. In this study, we examined whether people with central vision loss similarly rely primarily on the horizontal components of face images for face identification. Seven observers with central vision loss (mean age = 69 ± 9 [SD]) and five age-matched observers with normal vision (mean age = 65 ± 6) participated in this study. We measured observers' accuracy for reporting the identity of face images spatially filtered using an orientation filter with center orientation ranging from 0 (horizontal) to 150° in steps of 30°, with a bandwidth of 23°. Face images without filtering were also tested. For all observers, accuracy for identifying filtered face images was highest around the horizontal orientation, dropping systematically as the filter orientation deviated from horizontal, and was the lowest at the vertical orientation. Compared with control observers, observers with central vision loss showed (1) a larger difference in accuracy between identifying filtered (at peak performance) and unfiltered face images; (2) a reduced accuracy at peak performance; and (3) a smaller difference in performance for identifying filtered images between the horizontal and the vertical filter orientations. Spatial information around the horizontal orientation in face images is the most important for face identification, for people with normal vision and central vision loss alike. While the horizontal information alone can support reasonably good performance for identifying faces in people with normal vision, people with central vision loss seem to also rely on information along other orientations.