To add my anecodote. We are doing dives with over 1 hour deco. In nearly all instances I get a myopic shift, but its very subtle. This is on open circuit. Once it was very bad, down to 20/50. However, since I stopped exhaling 02 into my mask, the shift hasn't been as bad.

The difference can be very subtle, but while I notice it subjectively, it can be tested with some objectivity using a Snellen chart.

There are charts calibrated for Internet users.

May I suggest you folks check your eyes before and after a dive holiday and get a quantitative reading of the change? I think this shift is very common, more common that is listed in the medical literature.

http://www.mdsupport.org/snellen.html

Its important to make sure the letter size is correct and the subject is standing the proper distance away from the computer monitor, and test one eye at a time using your everyday lenses.

The chart is in metric, but follow the instructions to convert to US units if needed.