Saw my GP yesterday who checked my eyes again (checked 3 weeks ago) and also tested my neurological function .... all clear. She thinks the episode of double vision was probably due to a temporary failure of my eye muscles to work in unison. If this should happen again she suggests that I cover each eye in turn to see if the 'double' image resolves with one eye covered.
"The 2 most common mechanisms for diplopia are ocular misalignment and ophthalmic aberrations (ie, defects of the cornea, lens, iris or retina). The most important clue to the identification of the mechanism is whether the patient has monocular or binocular diplopia. Ocular misalignment in a patient with normal binocular vision results in binocular diplopia, defined as diplopia that resolves when either eye is occluded. If the image of an object that is being viewed does not fall on the fovea of both retinas, then the image appears to be in 2 different spatial locations and diplopia occurs.
Monocular diplopia is defined as double vision that is present in the affected eye while the other eye is occluded. In nearly all circumstances, monocular diplopia is the result of a local ocular aberration of the cornea, iris, lens or, rarely, the retina. Monocular diploplia is never caused by misalignment of the eyes."
So the explanation for my brief episode of double vision was nothing to do with Feckit after all ...... GREAT news!