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Russell L Woods, Francisco Costela, Dylan J Rose, Daniel R Saunders, Sidika Kajtezovic; Video Scanpath with Central Vision Loss. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2483.
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© ARVO (1962-2015); The Authors (2016-present)
Most people with central vision loss (CVL) report difficulty watching video, on TV, computers and in the cinema. People with full sight look in about the same place most of the time when watching directed content such as “Hollywood” movies and TV programming. We asked whether people with CVL look in the same places and whether that is related to the reported difficulty.
Subjects with CVL (n=16), with normal vision (NV; n=60), and with NV that was blurred by defocus (n=15) watched short (30s) video clips. Blur reduced visual acuity to about 20/50, 20/125, 20/320, or 20/800, which matched the range of visual acuities of the CVL group. Scanpaths coherence was measured using the normalized scanpath salience (NSS) method that compares each scanpath to a control group. To test whether there was a disadvantage to the scanpath of a person with CVL, in a second study, 351 on-line participants with NV watched clips on which a restricted region was visible, and that matched either the scan path of the normal vision group or that of a person with CVL.
Subjects with CVL made longer fixations and shorter saccades than the NV group. Subjects with CVL had lower NSS scores than the NV subjects, indicating that they were not looking in the same places at the same times. NSS scores of NV subjects with defocus were very similar to NSS scores without defocus and were higher than subjects with CVL with similar visual acuity. Thus, blurred vision alone is not the cause of the altered scanpath with CVL. When viewing the NV scanpath restricted-area clips, subjects were more able to follow the story than when viewing the CVL-scanpath clips. As, the CVL scanpath was less informative, it suggests that the “poor” scanpath is related to the difficulty watching TV.
Difficulty with video content experienced by people with CVL seems to be caused by difficulty with eye movement control. This suggests that rehabilitation methods that rely on the person with CVL locating and looking at the objects of interest may not be successful.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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