Autonomous navigation in novel environments still represents a challenge for people with visual impairment (VI). Pin array matrices (PAM) are an effective way to display spatial information to VI people in educative/rehabilitative contexts, as they provide high flexibility and versatility. Here, we tested the effectiveness of a PAM in VI participants in an orientation and mobility task. They haptically explored a map showing a scaled representation of a real room on the PAM. The map further included a symbol indicating a virtual target position. Then, participants entered the room and attempted to reach the target three times. While a control group only reviewed the same, unchanged map on the PAM between trials, an experimental group also received an updated map representing, in addition, the position they previously reached in the room. The experimental group significantly improved across trials by having both reduced self-location errors and reduced completion time, unlike the control group. We found that learning spatial layouts through updated tactile feedback on programmable displays outperforms conventional procedures on static tactile maps. This could represent a powerful tool for navigation, both in rehabilitation and everyday life contexts, improving spatial abilities and promoting independent living for VI people.

Background The estimation of relative distance is a perceptual task used extensively in everyday life. This important skill suffers from biases that may be more pronounced when estimation is based on haptics. This is especially true for the blind and visually impaired, for which haptic estimation of distances is paramount but not systematically trained. We investigated whether a programmable tactile display, used autonomously, can improve distance discrimination ability in blind and severely visually impaired youngsters between 7 and 22 years-old. Methods Training consisted of four weekly sessions in which participants were asked to haptically find, on the programmable tactile display, the pairs of squares which were separated by the shortest and longest distance in tactile images with multiple squares. A battery of haptic tests with raised-line drawings was administered before and after training, and scores were compared to those of a control group that did only the haptic battery, without doing the distance discrimination training on the tactile display. Results Both blind and severely impaired youngsters became more accurate and faster at the task during training. In haptic battery results, blind and severely impaired youngsters who used the programmable display improved in three and two tests, respectively. In contrast, in the control groups, the blind control group improved in only one test, and the severely visually impaired in no tests. Conclusions Distance discrimination skills can be trained equally well in both blind and severely impaired participants. More importantly, autonomous training with the programmable tactile display had generalized effects beyond the trained task. Participants improved not only in the size discrimination test but also in memory span tests. Our study shows that tactile stimulation training that requires minimal human assistance can effectively improve generic spatial skills. Electronic supplementary material The online version of this article (10.1186/s12984-019-0580-2) contains supplementary material, which is available to authorized users.

Pin-array displays are a promising technology that allow to display visual information with touch, a crucial issue for blind and partially sighted users. Such displays are programmable, therefore can considerably increase, vary and tailor the amount of information as compared to common embossed paper and, beyond Braille, they allow to display graphics. Due to a shortage in establishing which ideal resolution allows to understand simple graphical concepts, we evaluated the discriminability of tactile symbols at different resolutions and complexity levels in blind, blindfolded low-vision and sighted participants. We report no differences in discrimination accuracy between tactile symbols organized in 3x3 as compared to 4x4 arrays. A metric based on search and discrimination speed in blind and in low-vision participants does not change at different resolutions, whereas in sighted participants it significantly increases when resolution increases. We suggest possible guidelines in designing dictionaries of low-resolution tactile symbols. Our results can help designers, ergonomists and rehabilitators to develop usable human-machine interfaces with tactual symbol coding.

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