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M. Yao-N'Dre, F. Vitu, E. Castet; Role of Fixation Instability When Reading Continuous Text With an Artificial Macular Scotoma. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3069.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies showed a high correlation between decrease of reading speed in patients with macular scotomas and increase in the number of fixations needed to read a sentence. Our purpose was to test if this increase in the number of fixations could be the consequence of a detrimental oculo-motor instability due to the absence of visual input from the fovea.
Ten normally-sighted participants’ reading performance and eye-movements were recorded while they read aloud one-line sentences displayed on a textured background. We used a gaze-contingent display to simulate a scotoma masking the upper visual hemifield and forcing observers to read with the lower part of their visual field at a minimal eccentricity of 3°. In the control condition, the mask was uniform. In experimental conditions, an aperture within the mask revealed the underlying background, thus preserving foveal vision (image 1: red cross = gaze location).
Results showed no significant difference in reading speed and ocular patterns (fixation duration, frequency, direction and amplitude of saccades) between control and experimental conditions. An additional analysis revealed that the 2D distribution of fixation locations was not homogeneous along the line of text but revealed clusters located near low-frequency words.
These results suggest that oculo-motor instability due the absence of foveal stimulation is not a major limiting factor of reading speed in patients with macular scotomas.
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