Reading Pixelized Paragraphs of Chinese Characters Using Simulated Prosthetic Vision
ABSTRACT Visual prostheses offer a possibility of restoring useful reading ability to the blind. The psychophysics of simulating reading with a prosthesis using pixelized text has attracted attention recently. This study was an examination of the reading accuracy and efficiency of pixelized Chinese paragraphs after different parameters were altered.
Forty native Chinese speakers with normal or corrected visual acuity (20/20) participated in four experiments. Reading accuracy and efficiency were measured after changing the character resolution, character size, pixel dropout percentage, number of gray levels, and luminance.
A 5° × 5° character appeared to be the optimal size necessary for accurate pixelized reading. Reading accuracy close to 100% could be achieved with 10 × 10 pixels/character and ∼60% with a 6 × 6 pixel resolution. Pixel dropout adversely affected accuracy, and paragraphs with a 50% dropout were unreadable. Luminance had little effect; however, the number of gray levels significantly affected reading performance. Paragraph reading was at least 5% more accurate at each resolution than was the accuracy of Chinese character recognition.
Character size and resolution, pixel dropout, and the number of gray levels clearly affected the reading performance of pixelized Chinese paragraphs. Compared with pixelized character recognition, pixelized Chinese paragraph reading achieved higher accuracy; thus, optimal Chinese reading performance may require prostheses with more electrodes (1000) than are required to read paragraphs in the Latin alphabet (500).
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ABSTRACT: Rapid, accurate reading is possible when isolated, single words from a sentence are sequentially presented at a fixed spatial location. We investigated if reading of words and sentences is possible when single letters are rapidly presented at the fovea under user-controlled or automatically controlled rates. When tested with complete sentences, trained participants achieved reading rates of over 60 wpm and accuracies of over 90% with the single letter reading (SLR) method and naive participants achieved average reading rates over 30 wpm with greater than 90% accuracy. Accuracy declined as individual letters were presented for shorter periods of time, even when the overall reading rate was maintained by increasing the duration of spaces between words. Words in the lexicon that occur more frequently were identified with higher accuracy and more quickly, demonstrating that trained participants have lexical access. In combination, our data strongly suggest that comprehension is possible and that SLR is a practicable form of reading under conditions in which normal scanning of text is not possible, or for scenarios with limited spatial and temporal resolution such as patients with low vision or prostheses.Frontiers in Neuroscience 10/2012; 6:158. DOI:10.3389/fnins.2012.00158This article is viewable in ResearchGate's enriched formatRG Format enables you to read in context with side-by-side figures, citations, and feedback from experts in your field.
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ABSTRACT: PURPOSE. A VISUAL PROSTHESIS MAY ELICIT AN IRREGULAR PHOSPHENE MAP RELATIVE TO A REGULAR ELECTRODE ARRAY. THIS STUDY USED SIMULATED IRREGULAR PHOSPHENE MAPS AS A WAY OF OPTIMIZING THE DISPLAY METHODS OF CHINESE CHARACTERS (CCS) TO IMPROVE RECOGNITION AND READING PERFORMANCE. METHODS. TWENTY SUBJECTS WITH NORMAL OR CORRECTED SIGHT PARTICIPATED IN TWO EXPERIMENTS (9 FEMALES, 11 MALES, 20-30 YEARS). EXPERIMENT 1: two character display methods were proposed: selecting phosphenes covered by character strokes on a simulated phosphene array (projection method) and finding the phosphene closest to the expected location in some range of an irregular phosphene array as a substitute (nearest neighbor search (NNS) method). CCs' recognition accuracy was investigated using 6 levels for the coverage ratio of stroke and phosphene area and for search range, respectively, for two methods, for several irregularity levels. Experiment 2: reading accuracy (RA) and efficiency (RE) were measured using the regular array correspondence and NNS methods. RESULTS. EXPERIMENT 1: projection and NNS methods were significantly affected by coverage ratio or search range. NNS significantly improved CC recognition accuracy to highest at 81.3%±2.7% and 59.1%±5.2% respectively for different irregularity levels, compared with the projection method. Experiment 2: RA and RE significantly decreased as distortion level increased; NNS significantly improved RA ( from ~40% to >80%) and RE (from ~13 char/min to >40 char/min) when reading more irregular paragraphs. Conclusions. The performance of CC recognition and paragraph reading when using an irregular phosphene array can be improved through optimizing the display method.Investigative ophthalmology & visual science 04/2013; 54(4). DOI:10.1167/iovs.12-11039 · 3.43 Impact Factor
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ABSTRACT: Simulated prosthetic vision (SPV) in normally sighted subjects is an established way of investigating the prospective efficacy of visual prosthesis designs in visually guided tasks such as mobility. To perform meaningful SPV mobility studies in computer-based environments, a credible representation of both the virtual scene to navigate and the experienced artificial vision has to be established. It is therefore prudent to make optimal use of existing hardware and software solutions when establishing a testing framework. The authors aimed at improving the realism and immersion of SPV by integrating state-of-the-art yet low-cost consumer technology. The feasibility of body motion tracking to control movement in photo-realistic virtual environments was evaluated in a pilot study. Five subjects were recruited and performed an obstacle avoidance and wayfinding task using either keyboard and mouse, gamepad or Kinect motion tracking. Walking speed and collisions were analyzed as basic measures for task performance. Kinect motion tracking resulted in lower performance as compared to classical input methods, yet results were more uniform across vision conditions. The chosen framework was successfully applied in a basic virtual task and is suited to realistically simulate real-world scenes under SPV in mobility research. Classical input peripherals remain a feasible and effective way of controlling the virtual movement. Motion tracking, despite its limitations and early state of implementation, is intuitive and can eliminate between-subject differences due to familiarity to established input methods.