Eye-hand Coordination Using Irregular Phosphene Maps In Simulated Prosthetic Vision

Blindness is one of the most serious diseases of human. Scientists havepursuing the goal of helping the blind people receive visual perceptionagain for generations. Visual prostheses provide a promising approach torestore vision for the blind people. Among the different types of visualprostheses, the retinal implant has made the most progress in clinical trials.Clinical trials reported different irregular characteristics of phosphenemap elicited by retinal prostheses due to the complex spatial distribution ofneurons and their axons in retina. This study summarized irregularcharacteristics of phosphene map and designed a prosthetic visionsimulating system using three irregular characteristics: distortion, dropoutand irregular shape. Then this study investigated effects of the threeirregular characteristics on two eye-hand coordination tasks (geometricshape drawing and Chinese character writing) and the learning effects ofboth tasks under simulated prosthetic vision.24volunteers with normal or corrected visual acuity of20/20participated in the two tasks: drawing geometric shapes and writingChinese characters on a touch screen. The accuracy and efficiency in bothtasks were investigated while one irregular characteristic (distortion,dropout percentage or irregular shape percentage) was changed.Furthermore, the learning effect of the two tasks under phosphene mapwith a mixture of irregular characteristics was also studied by repeating thetwo tasks until the performance saturated.The results show that the performance of the drawing task is obviouslybetter than that of the writing task. The accuracy and efficiency of both tasks decreased as the variability of distortion, dropout and irregular shapeincreased. Distortion and dropout percentage had significant effects on theperformance of the two tasks, while irregular shape did not significantlyaffect the results. Besides, under the phosphene map of combinedparameters, the performance in the drawing and writing task increased tothe level that could be achieved under regular phosphene map after15and30trials of practice respectively.In conclusion, this study investigated the effects of irregularcharacteristics of phosphene map on eye-hand coordination task anddemonstrated that performance of eye-hand coordination task undersimulated prosthetic vision could be improved after practice.