Hate to bring up an old thread, but I found this through a Google search if 'Palinopsia' or after-images can come about from eye strain.
Not sure if you are still somewhat active here enough to see this reply but, I will say worrying about anything when you're even mildly afraid of it in an anxious manner seems to never turn out well and only results in something unwanted.
I was doing okay for a few months not worrying much anxiety-wise, and I made the mistake of drinking some caffeine again, which triggered some heart anxiety again, then proceeding into seeing all this weird stuff like way more after-images, more floaters, and the thing I've experienced before extensively due to depression and anxiety, peripheral hallucinations.
To anyone reading this, never worry about dumb things like this if the doctors tell you nothing is legitimately wrong. It only makes things worse.
I visit a doctor for a new physical in a few weeks, and haven't done something of the sort in years. Therefore, I cannot say for sure what I believe but, I spend nearly 10-14 hours a day on the computer, and most days of the week stay inside. My eyesight has noticeably deteriorated after doing this for a couple years at this point. That doesn't bother me but, the eye strain is a problem. If you live this type of lifestyle and expect not to see weird things after some time like after images a lot or some visual clarity issues, you need a reality check. I believe it to be a reversible thing if you make sure to care for your eyesight from then on, but nonetheless.
Again, sorry to bring up an old thread, just thought I'd share my piece of mind in case anyone wonders.