As visual and hearing disabilities had almost nothing to do with heredity, once a member of the Todo-za was recognized for his achievements in heikyoku (a traditional musical narrative on the Tale of Heike), sangen (or samisen -a three ringed instrument) and acupuncture, the 73 ranks up to Kengyo were sequentially opened up to the blind officers after certain intervals of time.
また、視覚障害は世襲とはほとんど関係ないため、平曲、三絃や鍼灸の業績が認められれば一定の期間をおいて検校まで73段に及ぶ盲官位が順次与えられた。