title: Visual impairment, uncorrected refractive error, and accelerometer-defined physical activity in the United States.
abstract: OBJECTIVE
  To examine how accelerometer-measured physical activity is affected by visual impairment (VI) and uncorrected refractive error (URE).
  
  
  METHODS
  Cross-sectional study using data from the 2003-2004/2005-2006 National Health and Nutritional Examination Survey. Visual impairment was defined as better-eye postrefraction visual acuity worse than 20/40. Uncorrected refractive error was defined as better-eye presenting visual acuity of 20/50 or worse, improving to 20/40 or better with refraction. Adults older than 20 years with normal sight, URE, and VI were analyzed. The main outcome measures were steps per day and daily minutes of moderate or vigorous physical activity (MVPA).
  
  
  RESULTS
  Five thousand seven hundred twenty-two participants (57.1%) had complete visual acuity and accelerometer data. Individuals with normal sight took an average of 9964 steps per day and engaged in an average of 23.5 minutes per day of MVPA, as compared with 9742 steps per day and 23.1 minutes per day of MVPA in individuals with URE (P > .50 for both) and 5992 steps per day and 9.3 minutes/d of MVPA in individuals with VI (P < .01 for both). In multivariable models, individuals with VI took 26% fewer steps per day (P < .01; 95% CI, 18%-34%) and spent 48% less time in MVPA (P < .01; 95% CI, 37%-57%) than individuals with normal sight. The decrement in steps and MVPA associated with VI equaled or exceeded that associated with self-reported chronic obstructive pulmonary disease, diabetes mellitus, arthritis, stroke, or congestive heart failure.
  
  
  CONCLUSIONS
  Visual impairment, but not URE, impacts physical activity equal to or greater than other serious medical conditions. The substantial decrement in physical activity observed in nonrefractive vision loss highlights a need for better strategies to safely improve mobility and increase physical activity in this group.
authors.affiliation: Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Willis
authors.forename: Joan L
authors.initials: JL
authors.lastname: Jefferys
authors.forename: Susan
authors.initials: S
authors.lastname: Vitale
authors.forename: Pradeep Y
authors.initials: PY
authors.lastname: Ramulu
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009043:Motor Activity; D009749:Nutrition Surveys / Q000706:statistics & numerical data; D010809:Physical Fitness; D012030:Refractive Errors / Q000453:epidemiology* / Q000503:physiopathology*; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014786:Vision Disorders / Q000453:epidemiology* / Q000503:physiopathology*; D014792:Visual Acuity; D055815:Young Adult