Hello Nancy T. This is brainstorming and speculation on possible causes. Hopefully the extensive examinations you have had will exclude all or most of them. Corneal topography changes such as a cornea scar, keratoconus for instance, might cause monocular diplopia but it should not be exclusively positional like yours.
Possible causes (speculation):
1 Misalignment of the eye in downgaze-verticle heterophoria/tropia, thyroid eye disase, partially paretic (weak) vertically acting eye muscle, orbital pseudo-tumor, scarring or symblepharon of conjunctiva, vertical differences in the heights of the eyes/orbits, unstable cornea due to injury or refractive surgery,
2. Deformation of the cornea in one eye in down-gaze (some of the above could cause this) plus growth or tumors of the upper or lower eyelids.
3. Differences in the tear film height in downgaze (tear meniscus).
4. Holes in the iris (usually a laster iridotomy).
5. Optical defects such as bifocals that are not level, misalignment of the optical axis with the visual axis of the eye, looking through the lines on lined bifocal/trifocals, looking through blended area in no-line bifocals, irregular corneal astigmatism,
I'm glad that the 'odd' reading glasses corrected the problem.
JCH MD
P.S. Forgot to say that the ghosting does NOT disappear when I cover one eye or the other. The "height" of the shadow letters sometimes changes slightly depending on which eye is covered, but usually not.
Nancy T.
That additional information would eliminate the casues listed under 1 misalignment of the eys.
Wow, that's a lot of possibilities! But I realize the cause is unlikely to be determined for sure, after having seen two specialist eye MDs. I'm sure they ruled out lots of stuff, though giving little in the way of explanation or speculation (originally dryness and eyelids possibly needing to be pulled up were mentioned, but those apparently aren't the case).
No history of injury, surgery, and no bifocals, and whatever it is occurs pretty much equally in both eyes.
Thanks VERY much for taking the time to offer some speculations. My yearly exam is coming up and I'll see whether the ophthalmologist might have any new ideas. At the least, I'll get a second pair of those ghost-busting glasses! :)
Nancy T.
At my yearly exam with my ophthalmologist this week, I mentioned the theory of the cornea changing shape due to eyelid pressure when reading while looking down, but he didn't seem to think this was the case, or at least didn't say anything about it.
I got a good reminder the other day, in fact, that there is another thing besides reading that causes bad "ghosting," namely being sleep-deprived. I got only 4 hours sleep for two nights in a row (finishing a project) and the ghosting was pretty bad with NO reading at all. Hmmm.
Nancy T.
A related discussion,
vertical ghosting was started.
A related discussion,
Note for nancy was started.