thank's for replay Ruud.
I'm sorry but I'm lost in translation, and it's hard to explain what I feel.
Ok: with/without glasses i have blackouts, i have to force myself to keep the eye physically wide open to avoid blackouts, and I have to stay at a precise and perpendicular distance. I also have the feeling that the diameter of the outer glass of the eyepiece is too large and ruin the comfort. But I had the same problem with some binoculars.
Another example: with the eyepiece copy of the Planetary ED 25 I have no problem about blackouts even during the day, they are very relaxing even in long sessions, i can rest my eye and relax. Here no, i must always keep it wide open, as soon as I relax it for a second ... blackouts coming, that's why I thought of the eyepiece exit pupil. Maybe only pentaxes are similar to planetary ED as a solution?