The NPB announced a rule change for Nagoya Dome and Tokyo Dome on Wednesday.
Up until last year, if a baseball hit the ceiling, regardless of where it hit the ceiling, it was still considered in play. Umpires then judged if a ball was fair or foul once it hit the ground, or touched a fielder. Beginning this year, balls will only be considered in play if they hit the ceiling over the actually playing field.
The rules will go into effect beginning with the exhibition games.