By Micah Maidenberg

MetLife Inc. said it agreed to purchase Versant Health for about $1.68 billion in cash, a deal the company said would turn it into one of the largest vision insurers in the U.S. and further a diversification push.

MetLife on Thursday said it would purchase Versant from an investor group that includes Centerbridge Partners and FFL Partners.

Versant owns Superior Vision and Davis Vision, which provide a range of vision-care benefits, including coverage plans for employers. Overall, Versant has roughly 35 million members, and MetLife's existing customers would gain access to Versant's provider network.

The acquisition would make MetLife the third biggest vision insurer in the U.S. based on the number of members, it said in a statement. The planned acquisition would also bolster the company efforts to add new products to its insurance and financial-services lineup.

"This transaction will build on MetLife's recent expansions of its product suite into pet insurance, digital estate planning, and health savings and spending accounts," MetLife said in a statement.

MetLife has offered group vision insurance since 2012.

MetLife said it would use cash on hand to buy Versant and is targeting completing the deal by the fourth quarter. The acquisition is expected to add to its earnings on a per-share basis, MetLife said.

Write to Micah Maidenberg at micah.maidenberg@wsj.com