ANSWER: Making some change to allow you to function in your current job is "accommodation." Placing you in another job in which you can function is "reassignment." Government policy dictates that disability retirement be a last resort. (That does not diminish the fact that it is also your right if you meet the legal criteria.) Because it is a last resort, your agency is required to make a reasonable attempt either to allow you to continue working in your present job or to reassign you to another job. Included in the OPM application is Form 3112 D titled "Agency Certification of Accomodation"
Accommodation may involve modifying the work site, adjusting the work schedule, restructuring the job, etc. To be a valid accommodation, it must allow you to perform all the critical elements of your job, regardless of your medical disability. A valid reassignment must be an offer of another position in your agency at your grade, pay and tenure, within your commuting area. The new job reassignment must be one in which you can perform satisfactorily despite your disabling symptoms.
Only after efforts to accommodate or to reassign have been attempted and have failed, can the agency move your case to OPM for disability retirement consideration.
Example: Edna became hypersensitive to tobacco smoke, causing her to suffer from disabling symptoms such as nausea, dizziness, and headaches. Her agency tried to accommodate her by moving her to a non-smoking office. When that didn't work, she was placed on a smoke-free floor. Edna still got sick from the trace amounts of tobacco smoke she encountered in the hallways and elevators. Apart from her hypersensitivity to tobacco smoke, Edna was perfectly healthy. Edna was legally disabled. The agency has made greater accommodation efforts than is customary. If she meets the other requirements, Edna would be entitled to disability retirement.