Thanks for the info. My plan is to find an Opthalmologist in this country equipped to do one of the tests described, and see how I get on. If ok, I'll see if any of the FAA AMEs in this country have that equipment; otherwise I'll apply to Oklahoma City to either find out where I can get tested, or, if they will accept the test as carried out by the above Optho. and remove the restriction.
If I can't pass the test then I guess the next step would be to apply to Ok. City to find out where I can do a SODA.