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Francisco M. Costela, Sidika Kajtezovic, Russell L. Woods; The Preferred Retinal Locus Used to Watch Videos. Invest. Ophthalmol. Vis. Sci. 2017;58(14):6073-6081. doi: https://doi.org/10.1167/iovs.17-21839.
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© ARVO (1962-2015); The Authors (2016-present)
Eccentric viewing is a common strategy used by people with central vision loss (CVL) to direct the eye such that the image falls onto functioning peripheral retina, known as the preferred retinal locus (PRL). It has been long acknowledged that we do not know whether the PRL used in a fixation test is also used when performing tasks. We present an innovative method to determine whether the same PRL observed during a fixation task was used to watch videos and whether poor resolution affects gaze location.
The gaze of a group of 60 normal vision (NV) observers was used to define a democratic center of interest (COI) of video clips from movies and television. For each CVL participant (N = 20), we computed the gaze offsets from the COI across the video clips. The distribution of gaze offsets of the NV participants was used to define the limits of NV behavior. If the gaze offset was within this 95% degree confidence interval, we presumed that the same PRL was used for fixation and video watching. Another 15 NV participants watched the video clips with various levels of defocus blur.
CVL participants had wider gaze-offset distributions than NV participants (P < 0.001). Gaze offsets of 18/20 CVL participants were outside the NV confidence interval. Further, none of the 15 NV participants watching the same videos with spherical defocus blur had a gaze offset that was decentered (outside the NV confidence interval), suggesting that resolution was not the problem.
This indicates that many CVL participants were using a PRL to view videos that differed from that found with a fixation task and that it was not caused by poor resolution alone. The relationship between these locations needs further investigation.
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