An exerpt from EEOC:

http://www.eeoc.gov/types/ada.html

A qualified employee or applicant with a disability is an individual who, with or without reasonable accommodation, can perform the essential functions of the job in question. Reasonable accommodation may include, but is not limited to:

* Making existing facilities used by employees readily accessible to and usable by persons with disabilities.
* Job restructuring, modifying work schedules, reassignment to a vacant position;
* Acquiring or modifying equipment or devices, adjusting or modifying examinations, training materials, or policies, and providing qualified readers or interpreters.

An employer is required to make a reasonable accommodation to the known disability of a qualified applicant or employee if it would not impose an "undue hardship" on the operation of the employer's business. Undue hardship is defined as an action requiring significant difficulty or expense when considered in light of factors such as an employer's size, financial resources, and the nature and structure of its operation.

An employer is not required to lower quality or production standards to make an accommodation; nor is an employer obligated to provide personal use items such as glasses or hearing aids.