Suddenly going dark in dark room.

Yesterday, when i went from a brightly lit room to a dark room i  could not see from one eye. But this was very clearly just from my right eye i have more power and astamagitism  in my right eye, compared to left and i was not wearing my spectalcles. However after i came back in light, rested my eyes for a few second and went in dark again, this time it was normal. I could see as i normally do.  This has never happened before. My eyes were also tired from reading and screen use. Also is it normal to see dark spot overcoming in your filed of vision that gradually increases after you try to concentrate of something vv small say a dot on the wall for over 10 seconds? It goes awaay if i blink. I had my ratina checked lawt year in july due to floaters, and tge ratina specialist said everything was fine. I see no floaters anymore. I sthis concerning or just my eye power has increased?