Tens of thousands of Medicare patients receive unnecessary cataract, gall bladder, prostate, back, hernia or other surgeries, and the financially hard-pressed program could save up to $1.2 billion a year by eliminating nine types of excess operations, according to a report by the Senate Special Committee on Aging.

The panel said 10 states have adopted "second-opinion" requirements for their Medicaid programs, in which a patient advised by a physician to obtain surgery must seek the advice of a second one before going ahead with the elective surgery. The report said the incidence of surgery had dropped notably as a result, with substantial savings.

Based on that experience and other studies, the committee estimated that using a mandatory second-opinion program in Medicare, which the Reagan administration opposes, would cut 17 to 35 percent from the $3.7 billion expected to be spent by Medicare on nine surgical procedures this year.

A spokesman for the Health Care Financing Administration, which administers Medicare, said HCFA has a voluntary second-opinion program and is not convinced that a mandatory one would achieve the savings projected, because many of the studies cited were based on younger populations.

The nine types cited were cardiac pacemaker surgery (up to 33 percent excess procedures), cataract surgery (up to 36 percent), gall bladder (up to 31 percent), prostate (up to 29 percent), knee surgery (up to 32 percent), hysterectomy (up to 45 percent), back surgery (up to 36 percent), hernia repair (up to 28 percent) and hemorrhoidectomy (up to 43 percent).