A South Florida eye surgeon who’s a friend of a U.S. senator is under federal criminal investigation for billing Medicare millions of dollars to treat elderly patients for services they may not have needed, The Miami Herald has learned.

Federal agents began investigating Dr. Salomon Melgen last year, sources say, after investigators suspected he overbilled the taxpayer-funded health program by overprescribing a high-priced drug called Lucentis, which is injected into patients’ eyes.

Several sources familiar with the doctor’s practice said he used the drug, which costs $2,000 a vial, to treat patients with macular degeneration more than any other ophthalmologist in Florida and possibly the country. His high patient volume also raised red flags for investigators, the sources said.

Under Medicare policies, a doctor may only prescribe treatment that is “reasonable” and “necessary.” To make a case, federal prosecutors would have to prove that Melgen needlessly treated patients simply to run up sky-high Medicare bills.

Melgen, whose lawyers have denied any wrongdoing, finds himself in the middle of two federal investigations: His Vitreo-Retinal eye clinics in West Palm Beach and two other South Florida sites were raided last week by agents with the FBI and the Department of Health and Human Services, who are investigating possible Medicare fraud. A separate FBI investigation revolves around the doctor’s relationship with U.S. Sen. Robert Menendez, D-N.J., and the trips they took on his private plane to Melgen’s villa at a resort in the Dominican Republic.

Lisa Strelec, a technician who has worked for Melgen for about 20 years, said the doctor’s West Palm Beach office was only closed for two days after the raid, when agents carted away boxes of financial records, patient charts and computer equipment. She vociferously defended Melgen as a dedicated, “wonderful” doctor who works 60 to 80 hours a week.

Strelec said that about 20 employees including herself readily gave the FBI interviews. She said FBI agents did not ask her any questions about Melgen’s personal life or other business ventures and investments. She said the agents only asked questions about Melgen’s practice, including the number of patients, insurance coverage and medical charts.

She said he treats patients -- mostly with diabetes, macular degeneration or retinal detachment -- on high-end plans and those who are poor. “He sees patients on Medicare, Medicaid, private,” she said. “He sees Spanish, white, black. The doctor sees every patient.”

State records show five patients have filed medical malpractice claims against Melgen, resulting in three settlements totaling $575,000. The remaining two claims were not settled, according to the Florida Office of Insurance Regulation.

MENENDEZ CONNECTION

Melgen donated more than $750,000 last year to Menendez’s reelection campaign and other political committees and candidates.

Menendez has insisted that he only took two personal trips on the doctor’s plane and recently reimbursed him $58,500 for the travel expense — but only after an ethics complaint was filed against him in New Jersey last year.

Of late, Menendez also has drawn media coverage for contacting Medicare officials to help resolve Melgen’s nearly $9 million billing dispute stemming from a 2008 audit. The administrative dispute revolves around claims filed by Melgen for his patients who received Lucentis.