I wear contacts and do the monovision thing...right eye is for distance and left eye is for reading up close.
I have been using my left eye all my life but just recently switched to using my right eye.
The reason being is that with the dioptor adjusted for my left eye anyone using my camera cannot see the subject in focus.
Now that I switched to my right eye I no longer need to adjust the dioptor to correct my vision and I can hand the camera to anyone to use without it being specific to my eye....sound confusing....