3D printing parameters for high-relief tactile 2D images: enhancing perception for users with visual impairment

PURPOSE: This research aimed to investigate the perception of visually impaired individuals regarding high-relief tactile 2D images produced by 3D printing, in order to identify design parameters (contour line height, line width and texture density) that optimize tactile comprehension. MATERIALS AND METHODS: An experiment was developed and applied to 28 participants with visual impairments. Tasks were designed based on skills whose foundations are needed and used in daily life, such as scanning, tactile discrimination, icon/object comprehension and copy finding. The tactile images were produced by additive manufacturing and printed on 180 g/m² sulphite paper, varying contour line height, line width and texture density. RESULTS: The best performances were obtained when: (1) contour line heights were between 0.2 and 0.4 mm; and (2) texture densities were between 10% and 50%, when used alone, or between 10% and 90%, when combined with another texture. The tested line widths (0.8 and 1.2 mm) did not show statistically significant differences. Vision status (low vision or blindness) and moment of vision loss (congenital or late blindness) did not influence the results; schooling, however, affected performance in object identification and copy location tasks. CONCLUSIONS: A detailed set of recommendations for the production and application of tactile materials is presented, ranging from the simplification of forms to the encouragement of bimanual exploration during content assimilation.