Sometimes it doesn't pay to fight Uncle Sam.

Back in September 1981 two major lens manufacturers -- Bausch & Lomb and Wesley-Jessen, a Chicago-based division of Schering-Plough Corp. -- announced on the same day that they planned to market a soft plastic bifocal contact lens. Both companies contended that they could put the product on the market without going through the Food and Drug Administration's testing procedures because they already had received its approval to sell both near- and far-vision contact lenses, the components of a bifocal lens.

"It's not, after all, like combining two drugs which can produce a third effect," a Schering spokesman said yesterday.

The FDA, however, disagreed.

The FDA requires that all contact lenses offered for sale be proved safe and effective with laboratory tests on the materials and clinical trials. In this case, since the material in the contact lenses had passed the safety test, the FDA was concerned primarily with whether they would work as bifocals. To show this, manufacturers were supposed to give samples to volunteers to see whether the lenses worked.

Bausch & Lomb decided it would go through the pre-market testing and Tuesday won the FDA's approval. The Rochester-based company announced yesterday that the lenses, which have been sold overseas since early this year, are available for distribution, 13 months behind the company's original schedule.

Wesley-Jessen fared worse. The company fought the FDA decision in court and lost, bringing a federal raid on its plant in February and seizure of $12,000 worth of lenses and other material. The U.S. District Court in Chicago ordered Wesley-Jessen to conduct the FDA tests before marketing its bifocal contacts.

The tests were successful and yesterday an FDA advisory committee recommended that the Wesley-Jessen lens receive the agency's approval, which could come in two to three weeks.

While the two companies fought the FDA, however, Ciba-Geigy, a late starter, quietly went through the testing procedures. In June, its brand of bifocal contact lens went on the market, giving it a head start of more than five months on its two major competitors.