I have been spending well over two years getting to grips with this problem. I am myopic, with a high prescription and have some bins that work well, but others that do not, including Swaros with 19 and 20mm specified eye relief.
In the thread "eye -relief rule of thumb method", Typo - for whom I have great respect for his binocular reviews, wrote:-
"It seems different companies tend to either use the true eye relief, the distance fron the lens to the exit pupil, and others the available eye relief, the distance from the rim of the eyecup to the exit pupil, as Pete describes. A minority seem to just make it up. Available eye relief, is obviously more useful for spectacle wearers and I wish more would adopt it. I suspect the reason some don't is that the true eye relief is part of the product's optical spectification and is covered by the relevant ISO standard. Interestingly it currently allows a 5.5mm tolerance around the specified value. I think that might drive all of us to despair."
Although I have succeeding in making a fix, once to a Swaro and once to a Zeiss, for inadequate eye - relief, it is generally difficult to overcome. I now have closer fitting frames but this solution brings, for me other problems.
Too much eye relief for specs wearers is relatively easy to fix, basically by putting O rings over the eyepiece tube to move the eyepiece rim further out. Err on the side of caution! I need different eye relief for each eye.
Opticron offers a wide range of binoculars, apparently measuring eye relief by the 'available method' see above.
'At infocus' and Opticron have demonstration days, some of which may be near you.
See
http://www.birdforum.net/showthread.php?t=337359&highlight=Events.
HTH
