Sugar Ray Leonard, who is scheduled to defend his world welterweight boxing title Friday, was admitted to Johns Hopkins University Hospital in Baltimore last night and placed in the world renowned Wilmer Eye Institute, it was learned.

Richard Peck, a spokesman for the hospital, said he could confirm that Leonard was admitted but was not authorized to divulge the reason. A source close to Mike Trainer, Leonard's attorney, said Leonard went to Hopkins for an eye examination. Another source confirmed early this morning that Leonard is in the Wilmer section at the hospital.

Early this morning, United Press International quoted an unnamed source as saying Friday's title defense would be postponed. Asked to respond, Trainer said, "No comment." A spokesman for ABC Television, which is scheduled to televise the fight during prime time, said he did not know anything about a postponement.

Trainer said he would have no comment until Monday, when a "totally complete and to the point" statement is planned, probably in Buffalo; that is where Leonard has been training for the fight against Roger Stafford. Trainer, who said he was complying with his client's wishes, would not say why Leonard had left training camp.

"He decided that at this point it's in everybody's best interests to keep everything private," Trainer said.

The ABC spokesman also said he was unaware that Leonard had been hospitalized. He said he was "999 percent sure" that no ABC official was aware of that, either.

Leonard, 25, left Buffalo, where he had been in midafternoon yesterday after a regular, light workout and normal press conference and autograph session, according to one of his security guards. The guard said he understood Leonard was returning home to Mitchellville, Md., to spend Mother's Day with his mother.

Contacted late last night in Buffalo, trainer Angelo Dundee, who works with Janks Morton in preparing Leonard, expressed surprise. Dundee said he had spent the day with Leonard "and everything was normal. I'm just amazed at this."

Ollie Dunlap, who supervises Leonard's training camp, said he expected the champion back in Buffalo for 7 a.m. road work Monday.

Leonard, from Palmer Park, Md., turned professional in 1977, after winning the light welterweight title in the '76 Summer Olympics. He is 32-1 as a pro, his only loss a 15-round decision to Roberto Duran in 1980.