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Susana T L Chung; Training to improve speed of letter recognition benefits reading speed in people with central vision loss. Invest. Ophthalmol. Vis. Sci. 2018;59(9):630. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Reading is slow and difficult for many people with central vision loss even with large print. Previous studies suggested that the visual span (number of letters recognizable in a glance) and the temporal threshold for letter recognition are two major factors limiting reading speed in people with central vision loss. Here, we asked whether or not temporal threshold for letter recognition could be improved through training in people with central vision loss; and if so, whether that would lead to faster reading speed.
Eight observers with central vision loss (age: 43–87, logMAR acuity: 0.36–1.1) participated in the study. A pre-test included (1) measurements of reading speeds using the rapid serial visual presentation paradigm (words presented one at a time) for five print sizes, from which the letter size used for subsequent testings was derived (1.4× the critical print size); (2) recognition accuracy of the middle letters of trigrams (three random letters) presented at fixation and for a range of stimulus durations, from which the baseline temporal threshold (corresponding to 80% accuracy) was determined; and (3) visual-span profile (recognition accuracy for letters presented at various letter slots left and right of fixation). Training consisted of six sessions (10 blocks/session, 50 trials/block) of recognizing letters of trigrams presented at fixation. Trigrams were initially presented at the baseline temporal threshold and was reduced by 0.1 log step when observers’ accuracies for recognizing the middle letters reached 80% or higher for four consecutive blocks. A post-test, identical to the pre-test, followed training.
Averaged across observers, temporal threshold reduced by 3.3× (from 0.33s to 0.1s) after training. This improvement was accompanied by a 44% increase in maximum reading speed. The correlation between changes in temporal duration and maximum reading speed was significant (r=0.65; p=0.03). The size of the visual span also increased (by 7.2 bits) after training, but the changes in visual span and temporal duration were not correlated.
Temporal threshold for letter recognition is amenable to training and can lead to faster reading speeds and larger visual spans. These findings support the hypothesis that temporal threshold is a bottleneck on reading speed and offer a practical means to improve reading speed in people with central vision loss.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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