According to these sources it seems that you may be right, Fluribus. I guess I assumed that if LCDs cause some people strain and headaches then it must have been imperceptably causing damage during the years leading up to the problems and, thus, I will eventually have these same issues unless I take preventative measures. Now that I am researching that assumption it seems that I was wrong and do not need to worry about it. The article I posted in my original post initially seemed to support this belief but now I see that the author's worsened eyesight could simply have been a result of age and did not necessarily imply a correlation between vision and LCDs. Does this mean my Kindle's only benefits to me are readability in bright sunlight and incredibly long battery life? Hmn.
Thank you all for discussing this and helping me to resolve this (non?) issue and concern. If anyone has any evidence that counters Fluribus and my sources above then please post them. (The third source does mention that one study found a correlation between computer usage and near-sightedness but I am unsure if that single study provides enough weight to counter the rest of this data.)
Based on this topic
these three qualities determine the usability of LCDs for reading. I do not know if those qualities are only important to those with sensitive eyes or if they also matter to others. Except for brightness since I know it bothers me to use a bright screen in a dark room.
PPI (pixels per inch)
Contrast & brightness
Flicker (either in the backlight or frames per second)