* Kusal Perera retires hurt after hit on helmet
* Karunaratne resumes knock on 46 (Updates with Karunaratne batting)
By Sudipto Ganguly
CANBERRA, Feb 3 (Reuters) - Sri Lanka opening batsman Dimuth Karunaratne has passed a concussion test and returned to the crease after being cleared to bat after being hit by a bouncer on the back of the neck during the second test against Australia.
The left-handed batsman was struck by a Pat Cummins delivery on Saturday. He was carried off in a neck brace after a lengthy delay and forced to retire hurt on 46.
The batsman was taken to hospital from where he was discharged after being cleared of any serious injury.
He resumed his innings on Sunday when Kusal Perera retired hurt on 29 after being hit on his helmet by fast bowler Jhye Richardson.
Perera tried to duck under a short delivery but was hit flush on the side of his head with the neck protector of his helmet flying off.
The left-hander continued batting after being twice attended by the team doctor and finally walked off the field an over later while appearing unwell.
He will need to undergo an ICC-mandated concussion test before he can resume batting.
The touring side had earlier resumed their first innings on the third day on 123-3, trailing Australia by 411 runs. The hosts lead the two-test series by 1-0 after winning the opening match in Brisbane by an innings and 40 runs. (Editing by Greg Stutchbury)