I have had VF's for many years now, they do take a bit of getting used to, but if after a week or two at the most, if you are still having trouble take them back. They may just need adjusting.
The first time I had VF's I was persuaded to have Zeiss lenses, had very little trouble getting used to them, just a few hours. Only once was I persuaded to try an alternative lens, they were awful, no where as good as the Zeiss. Mrs. P started having VF a couple of years ago and was instantly comfortable with them.
Zeiss lenses are expensive, but in my experience worth every penny, the vision is sharp right across the lens, I found with others that when I looked over my shoulder when driving the image was not sharp.