Wow, that sounds a LOT like my problem. I posted on it quite a while back, I think under the title "Shadow letters after reading" or something like that. Dr. Hagan gave me some theories.
I had seen an opthalmologist about it, who eventually called in the neuro-ophthalmologist, neither of whom had apparently seen this before, nor could they say what was causing it. They did determine (by having me look through a pinhole, which made the ghosting disappear) that it was a refractive problem and prescribed some reading glasses which prevent the ghosting from occurring when I read. The ghosting is vertical (shadow letters above the real ones), occurs when I read looking down (NOT when I read looking straight ahead, as on the computer), disappears abruptly when I tip my head upward to a certain angle, and is more noticeable with light images on a dark background.
It is in each eye separately (i.e., covering one eye doesn't make it go away). The ghosting also occurs spontaneously (without any reading) when I'm sleep-deprived, but reading (while looking down) always makes it worse. After I stop reading, the ghosting will gradually go away after half an hour or so. Another weird thing about it is that at times my left eye, after some fast reading, will get a very odd, overall "weak" sensation. "Weak" is not at all a good word to describe it, but I can't think of anything else. It's just a sensation, and it also disappears gradually when I stop reading.
I found an article by Golnik and Eggenberger titled "Symptomatic Corneal Topographic Change Induced by Reading in Downgaze" which sounded very much like what happens to me. But who knows.
I am 50 with normal eyes (just some nearsightedness and presbyopia), never had ANY eye problems until this started 4-5 years ago. It seems to be getting gradually worse. I doubt it's related, but I do have an 8-year history of some odd, unexplained neurological/muscular symptoms, dizziness, and unilateral sudden hearing loss when I sneezed, but nothign was ever diagnosed except "cranial neuropathy" on the basis of very abnormal auditory evoked potentials (also have bilateral trigeminal nerve symptoms). In the early years of the strange neuro symptoms, I got the "weak"-feeling left eye often, for no reason whatsoever--felt like it was not quite "awake" and like I wanted a toothpick to keep it open even though it wasn't closing. However, the ghosting doesn't seem to be any worse in the left eye than in the right.
If you ever get an explanation for this ghosting, PLEASE post it!
Nancy T.
Convergeance insufficiency and latent hyperopia are possibilities here. Other possibilities? I'm unsure. Could it be a medication side effect? Perhaps you have exophoria, poor convergeance, and glasses prescription is off? Problem may have something to do with occupations - such staring at the same computer screen all day. Unfortunately, I can't go much farther with helping you. It sounds like you need a very thorough exam by an ophthalmologist to look not only at the health of the eye but also so get the right pair of glasses. Good Luck.
Michael Kutryb, MD