The International Brotherhood of Police Officers called on Mayor Walter E. Washington yesterday to order "an independent and impartial medical evaluation" of former assistant police chief Tilmon B. O'Bryant, who was retired last week with a tax-free disability pension.

The police union contended that there was insufficient medical evidence to support a disability claim and that conflict of interest existed in the case. The union also asserted in a letter to the mayor that any contention that O'Bryant is "on the verge of a stroke" cannot be supported.

"It would certainly be a boon to the medical profession" if doctors could predict strokes in advance, union president Larry L. Simons said in the letter. In fact, Simons wrote, O'Bryant's "disability has yet to occur."

Dr. Robert F. Dyer, appearing on O'Bryant's behalf before the retirement board last Thursday, testified that O'Bryant suffers from hypertension and arthritis, and as a result of the stress of his job, would be subject to a stroke if he continued to work.

James Mandish, the city's deputy personnel director, said last night that there was no need for a re-examination of O'Bryant. He called the union's request "a smokescreen" devised by the IBPO to avoid commenting on more substantial issues.

"They have not addressed the problems within the system that result in such a high level of disability retirement, and that is (the) benefits that are perhaps expensive," Mandish said. "The fact is that they don't want those benefits lowered in any way."

Sen. Thomas F. Eagleton (D.-Mo.), whose subcommittee is studying disability retirements here, last week called the benefits for policemen and firemen in Washington "the most lavish of any city in the country," and said that the system is full of "egregious abuses."

More than 80 percent of retired policemen and firemen here are retired on disability, a figure disproportionately high compared to other major cities.

The IBPO told the Eagleton subcommittee last week that top level officials in the police and fire departments are given preferential treatment and whisked through the retirement system, while rank-and-file members have to wait months - even years in some cases - for their cases to be decided.

The union letter released yesterday is an extension of that complaint.

O'Bryant, 58, a 31-year veteran of the force, is scheduled to retire on a tax-free disability pension of about $33,000 a year. The Police and Firemen's Retirement and Relief Board voted 6 to 0 to grant his disability request. The pension will become effective in one to two weeks, if the case takes the normal amount of time to be processed.

Before the decision becomes final, the retirement board can reopen o case based on new evidence, and has done so in the past, according to boad chairman Pecy Bottle. Bottle gave no indication yesterday, however, that the board would reopen O'Bryant's case.

"Tilmon has served the city well." Mandish said last night. "Medical doctors have certified his disability . . . and the retirement board was satisfied."

George Harrod, the city's director of personnel, which has jurisdiction over the retirement board, said it would be "discriminatory" to reopen O'Bryant's case.

"He has followed the system as outlined in the D. C. Code and police regulations to the letter of the law. He has been voted on and he is going to be retired." Harrod said.

O'Bryant was unavailable for comment yesterday, as he has been since what was apparently a sudden decision to retire on disability 10 days ago. He brushed past reporters with a "no comment" en route to his retirement board appearance.

Simons, in his letter to the mayor, charged that O'Bryant's cose should be reexamined on the basis of:

"The extraordinary speed in which the retirement was processed."

"The clear conflict of interest which exists . . . between Chief O'Bryant's personal interest in a disability retirement and his official duties as administrative services officer of the Police and Fire Clinic."

"The lack of an independent physician's report to the retirement board on his condition, as is usually required for line officers."

"The fact that his maladies . . . have not been sufficiently determined to be aggravated by or related to the performance of his police duties."

Police Capt. Joseph Latello, administrator of the police and fire clinic, has said that he is aware of some clinic "hardship cases," patients who have been waiting a long time to be referred to the retirement board. Latella aid that he could comment no further because the clinic director, Dyer, is the man responsible for evaluating cases and sending them to the retirement board.

Dyer was unavailable for comment the operation of the clinic said that the workload at the clinic, and the need for reexaminations and the opinions of outside consultants all work against sending patients speedily to the retirement board.

These sources contend that this process, by its nature, should be thorough to provide an opportunity to weed out malingerers. The average wait, these sources claim, is two or three months. The IBPO alleges it is closer to six months.

Because Dyer has been unavailable for comment, it has not been possible to determine whether the cases of O'Bryant and fire chief Burton W. Johnson and police chief Maurice J. Cullinone all were expedited in their passage to the disability board. All received retirement approval within two weeks after it was determined that they intended to retire.

As to the union charges that no independent physician was used to evaluate O'Bryant, Harrod said last night that a consultant was involved for part of the diagnosis. He said he did not know who that consultant was. Battle said that it was unusal, although certainly not unprecedented, that Dyer himself would present a case to the board.

Dyer testified that O'Bryant sustained his disability in the line of the duty, and that testimony was critical in the board's decision to grant him a disability pension, according to informed sources.

Mandish said that the law, as it has been interpreted by courts here, makes it difficult for the retirement board to overrule clinic doctors. In most disability cases, including O'Bryant's, Johnson's and Cullinane's, the clinic's 12-member board of surgeons recommends that the applicant be certified as disabled.

Courts have said the burden of proof is then on the retirement board to show otherwise. The board is composed of seven members, including two doctors.

Mandish said he knew of no other retirement system, including federal ones, that placed the burden of proof on the evaluation board, rather than on the applicant.

Sources familiar with the operation of the clinic say that doctors there, while frequently skeptical of borderline complaints, often will recommend that a persistent applicant is disabled because the doctors are wary of possible malpractice suits.

As to the unions charge that there was a conflict of interest in O'Bryant's case because he was examined by his subordinates, city officials last night pointed out last night that he followed established procedures in gaining his disability retirement.