Transcranial direct current stimulation as a new method for changing the accommodative response of the eye

The aim of the present study was to test if the exposure to transcranial direct current stimulation (tDCS) would change the excitability of the visual cortex and influence an accommodative response of the ocular lens. Twenty four subjects were divided into two groups: real-stimulation of the occipital cortex in which participants were exposed to real stimulation (1 mA for 12 min), and sham in which subjects were tested with placebo stimulation. The results showed that tDCS might indeed influence accommodative response. The strongest and most evident effect was observed when a 3.0 D accommodative stimulus was used: anodal tDCS increased but cathodal tDCS – decreased the accommodative response. The second finding was that the effect of stimulation was dependent on the examined eye. The right eye with slightly lower visual acuity and weaker accommodative response in pre-test, responded more strongly than the left eye. The short-time tDCS might modulate excitability of the neurons in visual cortex and eye sensitivity, reflected in the change of accommodative response. The tDCS method may be considered a technique that could reinforce conventional active visual training to improve accommodative functions.