Yardley has been asked by doctors in Australia to come immediately for treatment after he had complained to them that he had difficulty focussing with his left eye.
Due to his commitments with the Sri Lanka team Yardley had been ignoring his troubled eye which had now worsened.
Yardley succeeded another former Australian Test cricketer Dav Whatmore as coach in February this year and is contracted till the next World Cup in England in 1999.
Since taking up the appointment Yardley has gone to New Zealand, Sharjah (Singer-Akai), India (Independence Cup) and West Indies.
Cricket Board sources quashed rumours that Yardley was leaving for good when they confirmed that he would return in time if medically declared fit, for the two-Test series against India, which follows at the completion of the Asia Cup on July 24.
Manager Duleep Mendis is expected to take over the dual role as manager cum coach until Yardley returns.
A final decision on this appointment is awaited till Sri Lanka captain Arjuna Ranatunga arrives on Sunday, after attending the International Cricket Council's (ICC) captains' meeting in London.