200 jobs are to go at the Bausch and Lomb plant in Waterford.
The announcement was made at a meeting with staff this morning with remaining staff are facing a 20% pay cut.
The company has said the cost reductions are needed to keep the plant open.
Workers will be called in for discussions from next Tuesday.
In a statement Bausch and Lomb said they are looking to bring the cost base of the Irish plant closer to that of their base in Rochester, New York as wage rates are currently over 30% lower there.