Impaired vision and the ability to take medications

OBJECTIVES: To assess relationships between vision (contrast sensitivity, stereopsis, visual acuity) and a performance-based measure of ability to implement new medications. DESIGN: Cross-sectional analysis; prospective cohort study. SETTING: Community-based. PARTICIPANTS: Three hundred thirty-five participants aged 73 to 82 in Year 3 of the Women's Health and Aging Study II, a representative sample of the two-thirds least-disabled community-dwelling women. MEASUREMENTS: Hopkins Medication Schedule Pillbox Ratio, a joint measure of accuracy and time, and a performance-based measure of ability to implement a prescription. Participants received written and verbal instructions for taking two medications and were directed to place pills in a pillbox accordingly. Vision assessments: contrast sensitivity (Pelli-Robson letter sensitivity chart), stereopsis (Randot Circles), and visual acuity (Early Treatment Diabetic Retinopathy Study eye chart). RESULTS: Forty-four percent (148/335) of women incorrectly placed one or both medications. Each vision measure was positively associated with Pillbox Ratio scores and varied with cognition and time to completion. Better visual acuity, contrast sensitivity, and stereopsis were each associated with better performance in women with poor cognition who filled the pillbox quickly. Additionally, better visual acuity was associated with better performance in participants with good cognition who filled the pillbox slowly; better stereopsis was associated with better performance in participants with poor cognition who filled the pillbox slowly and whose stereoacuity was below normal. CONCLUSION: Visual acuity, contrast sensitivity, and stereopsis should be considered potential risk factors for impaired ability to implement a medication regimen in older adults. Future research should investigate the role of vision, including contrast sensitivity and stereopsis, on performance of other instrumental activities of daily living.