SANZAR judicial officer Paul Tully imposed the lengthy suspension after a four-and-a-half-hour hearing this afternoon, the organisation confirmed.
The Russia international was cited after Waratahs captain Daniel Halangahu made a first-half complaint that team-mate Tom Carter had been eye gouged in the ruck.
Medical evidence showed that Carter, who played out the match and scored two tries in the 35-19 win, sustained a minor scratch to his eye.
Tully said there was enough evidence to support the allegation, but Byrnes' otherwise unblemished record saw the ban reduced from 12 weeks to 10.
Byrnes will not be available to play until the week 13 clash against the Western Force on May 20.