In order to objectively evaluate the eye strain due to reading, we investigated the change in refractive value of the lens of eye between before and after reading, as an index for the eye strain. The refractive value of lens was obtained as the reciprocal of the visual acuity that was measured with a vision analyzer.
For subjective evaluation, SSQ (Simulator Sickness Questionnaire) method was used to assess the subject's mental state. In this study, 12 subjects indicated the level of severity of the 14 symptoms that they were experiencing before and after reading texts. Each of the 14 symptoms was assessed on a four-point scale.
In the result of the objective evaluation, the change of refractive value of lens due to reading was larger on paper than on screen. There was no statistically significant difference in the change of refractive value for both eyes, superior eye and non-dominant eye in each medium.
However, the subjective evaluation showed that the subjects felt more eye strain due to reading on screen than on paper.