-Recent advances in 3D technology have been accompanied by increasing complaints of visual fatigue. The usual explanation for such fatigue is that accommodation and convergence are mismatched during stereoscopic vision.The aim of this study was to measure fixation distances between lens accommodation and convergence in young subjects while they viewed real objects and 3D video clips. Measurements were made using an original instrument. The 3D video clips were presented to subjects using a liquid crystal shutter glass system. The results showed that when viewing real objects, the diopter values of subjects' accommodation and convergence were similar and changed periodically. This measurement method was thus considered to be appropriate for the measurement of stereoscopic vision. We also investigated lens accommodation and convergence when subjects viewed 3D video clips. Both accommodation and convergence were found to move along with the virtual position of 3D video clips. Therefore, there was little discrepancy between accommodation and convergence during the viewing of 3D images.

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An experiment was conducted on the ease with which a car navigation system could be read by elderly, middle-aged and young people. 127 subjects (19-76 years of age) evaluated ease of reading of the displayed characters. The experiment evaluated characters displayed on a liquid crystal display (LCD) similar to those used in car navigation systems, and evaluated readability in 9 stages. Five character sizes for traffic terms and two languages (Japanese and English) were used in the experiment. The experiment was conducted with the LCD in 2 positions: directly in front of the subject and diagonal to the left (about 30 degrees). The results showed that the directly frontward position was significantly more readable than the position of diagonal to the left.

We report the results of 3 surveys of visual display terminal (VDT) users who took a minibreak during which they viewed a stereoscopic image of a repeating parallel pattern showing planets. The single image stereogram method employed is called Stretch Eye (TM), and we evaluated the effects of Stretch Eye (TM) on asthenopia. An accommodative relaxation of about 1 D was observed in participants while they were gazing at the image. The employees of 2 information technology companies were evaluated according to a visual analogue scale (VAS) for subjective symptoms of asthenopia and eyesight. The results showed that Stretch Eye (TM) was effective in easing visual fatigue due to VDT work and it improved eyesight under working conditions.