Abstract
Purpose :
When applied to primary visual cortex, anodal transcranial direct current stimulation (a-tDCS) has been reported to reduce crowding in peripheral vision indicating a potential therapeutic use for patients with central vision loss. To further assess the potential of a-tDCS as a vision rehabilitation tool, we tested the hypothesis that visual cortex a-tDCS, but not sham a-tDCS, would improve reading of Chinese characters presented to left lateral peripheral vision in normally sighted adults.
Methods :
Sentences of Chinese characters were presented one character at a time 10o to the left of fixation at various speeds and print sizes. Participants (n = 10, 60 to 73 yrs. of age) read the sentences out loud and character recognition accuracy was recorded. Accuracy data were fitted with a continuous linear piecewise function that rises and then flattens to estimate all combinations of print sizes and speeds that elicit 55% accuracy. The point where both linear functions meet denotes the critical print size (CPS), defined as the smallest print size eliciting the participant’s fastest reading speed. Using a double-blind, within-subject design, participants were then tested with sentences of print size and reading speed corresponding to 0.2 logMAR below the CPS on 2 stimulation days on which 20 mins of active or sham a-tDCS was applied to the visual cortex. Each test consisted of 15 sentences, and one test was administered before, during, 5 mins post, and 30 mins post stimulation. Reading accuracies were compared across time-points.
Results :
A within subjects ANOVA revealed no significant interaction between Stimulation Type (anodal vs. sham) and Time (pre, during, 5 min post and 30 min post stimulation) (F(3,27)=0.59, p=0.63).
Conclusions :
A-tDCS did not improve reading of Chinese characters in left lateral peripheral vision in normally sighted individuals. The effect of a-tDCS on reading of Chinese characters or other writing systems presented to other regions of the visual field, including inferior peripheral vision, is yet to be determined.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.