Mr. Salgado has filed a lawsuit in state court in Miami-Dade County. Among those sued was Infupharma, a compounding pharmacy that was said to have divided the Avastin into tiny doses. It is not clear what the relationship was between Infupharma and Chroniscript.

Another lawyer, Gary Alan Friedman, said he represented six patients, four of whom have already filed suit.

“They all have either significantly lost vision or have been blinded completely by the contamination,” Mr. Friedman said.

Infupharma said it would not discuss details because of the continuing investigation and litigation.

Genentech said it would not comment on the litigation, but said that it had always cautioned against use of Avastin in the eye.

“Avastin is not manufactured or approved and to date has not been proven safe for use in the eye,” a spokesman for the company said Tuesday.

While the company is being sued, it could benefit overall if the incidents discourage use of Avastin in favor of the far more lucrative Lucentis.

Eye doctors who use Avastin have played down concerns about the risk of bacterial contamination.

Dr. Philip Rosenfeld, a retina specialist at the University of Miami who pioneered the use of Avastin for macular degeneration, said the recent incidents apparently stemmed from careless procedures by pharmacies and should not discourage the use of the drug.

“It took six years for something like this to happen,” he said, noting that there have been more than two million injections of Avastin into eyes in the United States alone since the practice began in 2005.

A clinical trial sponsored by the National Eye Institute found that Avastin and Lucentis were equivalent in preserving or improving vision after one year.

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By ANDREW POLLACK