More than 1,100 jobs are at risk in Co Waterford after Bausch + Lomb announced plans to lay off 200 people and close the facility if agreement is not reached on 20% pay cuts for the remaining staff.
The company employs nearly 1,200 people at its facility in Waterford, making it the county's biggest private employer.
The company makes contact lenses and other eye-care products and has been in Waterford for more than 30 years.
In a statement, the company said substantial cost reductions will be required to keep the plant open.
It said discussions with staff and union representatives will begin next Tuesday and the company hopes to reach a decision in principle by 17 June.
Bausch + Lomb said it wants to bring the cost base of the Irish plant closer to that in Rochester, New York, where wage rates are more than 30% lower.
The company added that the consultation process, which will begin immediately, follows a group-wide review of the contact lens business.
The company confirmed that next week's talks will focus on proposals for around 200 redundancies and a 20% cut in pay.
It said the Government and IDA Ireland have both been briefed on the situation "as it applies to the future viability of the Bausch + Lomb Waterford Plant".
Minister for Jobs Richard Bruton has said he is working to ensure that the 900 jobs remaining at the company after redundancies are sought can be saved.
He said his department and the IDA have been working with the company for months to secure the future of the Waterford plant.
Bausch + Lomb, which employs 11,000 worldwide, was taken over last year by Valeant, which is Canada's largest drugmaker.
Its Waterford site is one of only two contact lens manufacturing plants operated by the company.
Senior managers were called to a meeting this morning, while trade union and staff representatives were summoned to a meeting this afternoon.
The union representing workers at the company said the first they knew about the job losses was when a meeting was called this morning.
SIPTU organiser Allen Dillon said that workers were devastated at the news that 200 jobs are to go and that the remaining 900 jobs are under threat if pay cuts are not accepted.
Speaking on RTÉ's News at One, Mr Dillon said the employees were all still "raw".
He said claims by the company that salaries were too high and comparisons with its plant in New York were unfair, as it was not comparing like with like.
The terms and conditions of the Waterford employees had been negotiated "over a long number of years", he said, adding that their disposable income had dropped in recent years.
Mr Dillon said that €30,000-€40,000 was the average salary in the plant.
Independent TD for Waterford John Halligan said it is "deeply disturbing" that Mr Bruton knew jobs were on the line for a number of months and did not bring it to the attention of the Dáil.
Mr Halligan said that given Waterford has been one of the worst-hit areas in the country for job losses since 2008, Mr Bruton needed to bring information he had about potential redundancies and pay cuts to the attention of local politicians.
Speaking on the same programme, he said a 20% cut in pay would be "unsustainable" for most workers at the plant.
Vice President of Manufacturing Angelo Conti said the review showed that Waterford's cost base "is substantially out of line with other plants within the Bausch + Lomb infrastructure".
He said because the company is trailing its competitors in the global market with a "distant fourth place in market share, the status quo is not sustainable".
Mr Conti said the company is faced with a "stark choice" of either restructuring in Waterford and securing its future, "or see the plant close".
He said the preference would be to retain Waterford as a contact lens manufacturing hub, but "we need to reach a decision either way very soon".