It has to do with the optical correctness, right?
First you need to know:
If you would be watching 'at distance' (in the optical branche this would be 6 meters) the axis of your eyes would be parralel. This is, if you'd have perfect visionary balance.
Most high curvature lenses are not as optically correct as Oakley is. Meaning they have more or less prismatic imbalance. To better understand this, try looking through a glass of water...
This imbalance causes your eyes to compromise this by, mostly, turning outwards. Imagine having to do this for the length of a cycling race, let's say some 6 hours.
The constantly compromising of your eyes might indeed cause an imbalance. Years ago I have helped a lot of people with simmilar problems by adding a little prismatic correction to their prescription. Some of our patients didn't go out on the street, because of these imbalance problems...