Paper vs e-readers: which causes more eye strain?

I've been a member of the Society for Imaging Science and Technology since the early 90's.  That's not to say I understand most of what is published in their Journal, the JIST published quarterly.  But I have the utmost respect for the imaging scientists that are constantly looking for ways to improve the quality of displays, cameras, printers, and readers.  And every once in a while I come across a research paper that even I can understand.

Such is the case with an article from the newest JIST studying the effect of different reading media on eye fatigue. Sonomi Inoue and Makoto Omodani from Tokai University in Japan set up the study.  Here's the premise:

Emerging progress in electronic display technologies has

already produced high performance television displays with

large and flat screens. Display technologies seem to have al-

ready successfully received customer satisfaction as television

screens. On the other hand, customers are often complaining

about displays as document screens. We still generally prefer

reading on paper than on electronic displays. Eye fatigue

is one of general disadvantages of reading on displays. Eye

fatigue is an essential subject to be solved for electronic

displays.

Inoue and Omodani looked at paper, electronic paper, and displays for their research.  They were looking to test the hypothesis that the digital display is the reason for eye fatigue when reading text. What they found was that the "impact of reading style"--whether the book was hand-held or stationary--had a big impact on eye fatigue.

The authors discovered earlier "a tendency that the hand-held reading style, regardless of reading medium, offer readers a favorable impression in terms of readability and fatigue" and sought to quantify that finding.  After determining now to measure eye fatigue they set out to see what they could find.

Their conclusions?

1. The free condition for media handling offers lower fatigue (statistically significant) than the fixed condition, regardless of the medium.
2. The media (reflective/emissive) showed no significant difference in terms of eye fatigue
3. Electronic media that can be hand held are expected to reduce eye fatigue.

If you want to read a bit more about the science behind your reading pleasure you can find the entire article here.