BACKGROUND. Medical decision making has evolved from a paternalistic, "doctor knows best system" to one of shared decision making between health care providers and patients. Shared decision making involves informed consent related to the proposed health care options and medical decision-making capacity by patients. Adults aged 90 and older are the fastest growing segment of the US population. Dementia prevalence increases dramatically among this group. Dementia may affect the ability of patients to participate in shared decision making. CASE REPORT. The case of a 91-year-old female rehabilitation inpatient with mild cognitive impairment, cataracts, and macular degeneration is presented. The case highlights key issues of informed decision making and medical decision-making capacity related to cataract surgery. Video examples of the assessment of cognitive and medical decision-making capacity are presented. Copyright © 2012 American Academy of Optometry.