Reading pixelized paragraphs of Chinese characters using simulated prosthetic vision.

School of Biomedical Engineering, Jiao Tong University, Shanghai, China.
Investigative ophthalmology & visual science (Impact Factor: 3.43). 06/2011; 52(8):5987-94. DOI: 10.1167/iovs.10-5293
Source: PubMed

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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