Eyeworld

EW NEWS & OPINION October 2016 33 Reference 1. Reinhart RM, et al. Electrical stimulation of visual cortex can immediately improve spatial vision. Curr Biol. 2016;26:1867–72. Just why the improvement occurs remains unclear. One possi- bility is that the stimulation brings the neurons closer to firing and action potential, Dr. Woodman said. "A neuron gets input and if it gets enough input, it will fire; by running this type of stimulation, we might just bring it closer to that threshold," he said. "In that way, it takes fewer photons coming in the eye for that neuron to cross the threshold and say, 'I have a vertical line in my receptive field.'" An alternative hypothesis is that it can be easier to measure the signal due to the volume of matter from increasing the amount of activity in a circuit or a system, Dr. Woodman said. The idea is that the stimulus is causing the neurons to fire more, and because they're firing more, they cross the line faster. Clinical possibilities From a clinical perspective, this has appeal for various conditions, Dr. Woodman thinks. "There are a num- ber of (visual) disorders for which we don't have good treatments," he said, adding that while investigators are working on stem cells and vari- ous drug treatments, for some condi- tions there is nothing yet. Currently, there are no known side effects to the approach, although investigators remain on guard here. "What we're excited about is this may be a way to get at some disorders that aren't treatable with drugs," he said. This is not the only work being done to improve vision at the level of the brain; Dr. Woodman cited training regimens. "If patients have impaired vision and we have them practice visual tasks for a long period of time, they'll get better at these tasks," he said. "What we think is exciting is we might be able to use this brain stimulation and see immediate improvement, instead of doing something that takes weeks or months." If they were able to pair the training and brain stimulation, there might be a synergistic effect. This might result in improvements that are faster than these techniques done alone and much more endur- ing, Dr. Woodman concluded. EW Editors' note: Dr. Woodman has no financial interests related to his comments. Contact information Woodman: geoffrey.f.woodman@vanderbilt.edu

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