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Michael D. Crossland, David P. Crabb, Gary S. Rubin; Task-Specific Fixation Behavior in Macular Disease. Invest. Ophthalmol. Vis. Sci. 2011;52(1):411-416. doi: https://doi.org/10.1167/iovs.10-5473.
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Persons with central scotomas frequently use a preferred retinal locus (PRL) in place of the damaged fovea to fixate a target. Here the authors use a novel statistical technique to determine whether the retinal locus used for fixating a point target is the same as that used for reading words.
Nine subjects with established macular disease and bilateral central scotomas were recruited. The retinal area used for fixating a point target and words of text was measured using a microperimeter. A nonparametric spatial statistical technique was used to identify whether fixation points were the same for each of these two tasks.
The spatial distribution of fixation points was different for point fixation and word reading in all subjects with macular disease (P < 0.01). Fixation stability was also poorer for the word reading task than the fixation task (P < 0.05). For control subjects without macular disease, the distribution of fixation was the same for each task (P > 0.3).
Fixation behavior in persons with macular disease is not the same for fixating a point target and for fixating words in a reading task. It cannot be assumed that measuring a patient's fixation to a discrete point target accurately simulates their fixation performance on other tasks.
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