G'day,
I have, as is the case with many older people, cataracts developing in both eyes, but, so far, they don't seem to be causing problems. However over the last year there have been numerous occasions when I have started to see a 'ghost' image either just under or over the horizontal element of the cross hairs in various NV scopes I use when hunting. [The vertical element is not affected.] This seems to be partly fatigue related in that I will start off seeing the cross-hairs very clearly. After a while I start to see a double image and nothing I can do by refocusing the objective or altering my head/eye position makes any difference. At that point I quit as I don't know how accurate my aim would be if I wanted to shoot at a fox. Reading Dr. Google I have discovered that this ghosting effect can be caused by "Dry eye disease" in which "tears aren't able to provide adequate lubrication for your eyes." Apparently the surface of the eye becomes rough and irregular as the tear film along the surface of your eyes dries out. This causes uneven transmission of light. Hence the fainter 'ghost' image just under the main image.
I wonder if any others have had a similar problem? In the mean time I'm off to the optometrist today for a basic review.
Jim