User blog comment:Theraven22/bankai's that should be revealed/@comment-1706259-20100330203939

1) Aizen himself said implied that blind people were immune to his Shikai; which Unohana figured out and he practically agreed with.

2) Sekkiseki stone weakens reiatsu but doesn't completely stop it. Rukia could feel reiatsu through the tower she was in (in Soul Society).

3) Aizen himself stated that his shikai affected the 5 senses; through the condition of seeing his hypnosis.