Depending on the particular person, computer monitors cause a certain amount of eye strain after a time period of continuos use. This was especially true for the old, bulky CRT monitors, which caused eye strain problems mainly due to flickering, as they refreshed the image tens of times a second but not enough for the eyes not to be affected. LCD screens present mostly a static image, but they emit light in a significant amount with regard to the environment illumination. This is almost always true: if an LCD screen is adjusted for matching the environment light, it becomes not readable anymore.
However, you don't have to rely on LCD screens for everything - especially if you are a programmer who passes his workday before one.
Why screens cause strain
With CRT monitors out of the way and flickering issues a thing of the past, the main problem with modern screens remains backlighting. The human eye can distinguish between a wide range of light intensity values, but only a small range at a time: it has to adapt quickly to the medium illumination value. If you turn off the illumination at night, after some seconds you'll start adapting and see objects more clearly (of course not with the same level of detail). While using a computer screen, the eyes continuosly adapts between the screen lighting level and the environmental one, many times a minute.
The bad news is we, as computer programmers, stare to a screen almost all day. As a starting point, a simple remedy is to establish forced breaks from coding sessions. We use the Pomodoro Technique for time management, which prescribes to get a break every 25 minutes; I have no scientific research to back this frequency as ideal, but empirically seems to work (better than random breaks) and it is also already built in by the time management technique.
The top ten ebook readers use e-ink nowadays, a technology which changes the configuration of tiny colored spheres to display text or images, without resorting to backlighting. E-ink works in the same way as real paper: the blank portions of an e-ink screen reflect natural light or light originated from an external artificial source.
LCD is good for rapidly changing renderings, for tasks such as seeing movies, coding or browsing the web. E-ink is good for books and other material, where the rendering changes only when you turn the page.A key feature of an ebook reader resides in its supported file formats: Pdf and EPub are a must. I chose Bebook Neo over the Kindle 2 available at the time not only because of the custom (I live in Europe) but also for the wide selection of formats available in the former, that does not require conversion of documents.
EPub is a dedicated standard with more expressive power than Pdf, but the latter is widely supported also on computers as it is an ubiquitous format.
With an ebook reader, you can buy books directly from the device in many cases, if it has an available Internet connection. This depends on the particular model, but it is a killer feature that is spreading fast. Programming books like Clean Code or Growing Object-Oriented Software can be available as a reference while you are commuting or in the office.
By the way, if you have checked the supported file formats before buying, you can already transfer your ebooks. Freely available ebooks like Cory Doctorow's (or mine) are usually distributed in Pdf or EPub, depending whether they are targeting the computer screen or readers. Ebooks where the original copyright is expired, like History of Western Philosophy, are even available in multiple formats on the web.
Reading is a delighting task for many of us, and we should take care of not transforming it in a straining activity by staring at a computer screen even in our free time.
I often downloads slides from university lectures or interesting talks that have happened around the world when I do not have time (or the ROI, or the possibility) to see a video of the presentation. Slides in Pdf are ideal for viewing on a reader, since they have a large text and no zooming problems, that sometimes happen with Pdf ebooks. You can even take annotations with many readers, like you would do on a printed handout.
Unfortunately, many university teachers provide slides in the infamous PPT format. You can easily convert them one at the time with OpenOffice.org, but I'm still looking for a batch solution.
I used to save interesting blog posts to read in Delicious, with a todo label, or to read them immediately when found. This lead me to batches of some hours on my netbook to empty my feed aggregator at the end of the week.
Now I have a different strategy. I use Instapaper and I have the Read Later bookmarklet saved in every machine, in Firefox-based bookmarks (not Delicious). I associated the keyword 'insta' to the bookmark, and now every time I want to store an article for reading it slowly without straining my eyes, I type CTRL-L insta <Enter> and it is stored in the Unread folder of Instapaper.
Than when I have time to read, I go to Instapaper.com and it generates for me an EPUB file with all the unread articles which I can transfer on my ebook. It also marks the articles as read, working as a second-order feed reader. Then I go to my sofa and fully immerse in reading without worrying (also without the opportunity to open new links, and never finish my reading session).
So we have seen that for every task different from coding, there is an alternative to the computer screen. If you experience eye strain, try some of these practices to reduce your computer time. Feel free to comment and tell us your experience with computer screens.