Monocular double vision is not a common symptom of MS. Typically it's because something is wrong with the eye itself. I've had problems with this in the past, and it's because of my contacts - my eyes get too dry.
Hi. A great site that lists all sorts of things that have symptoms similar to MS is the U. of Maryland med center - http://www.umm.edu/altmed/articles/multiple-sclerosis-000474.htm
Here is their list of visual disturbances possibilities-
Amenorrhea
Atherosclerosis
Bone Cancer
Brain Cancer
Cataracts
Diabetes Mellitus
Food Poisoning
Glaucoma
Hypertension
Hypoglycemia
Migraine Headache
Myeloproliferative Disorders
Preeclampsia
Roundworms
Stroke
Transient Ischemic Attacks
Varicella-Zoster Virus
As you see that is a very diverse list. The best thing you can do for your wife is to get her an appt with an MS specialist. This disease has so many variations and nuances that it takes someone focused exclusively on MS to keep up with all the possibilities.
I hope you'll come back and let us know if you have more questions.
Lulu
Has your wife seen a Neuro opthamalogist? They are Neurologists who deal with eye problems.
Alex