title: Eye and head movement alterations in naïve progressive addition lens wearers.
abstract: OBJECTIVE
  To examine adaptation to progressive addition lenses (PALs) by investigating eye and head movement strategies of individuals naïve to PAL wear; to determine whether adaptation is a short-term change in strategy or is maintained with continued PAL wear; to determine if adaptation strategies are different between PAL designs.
  
  
  METHODS
  Ten presbyopic individuals participated in a double-blind crossover study. Participants wore one PAL design for < or = 4 weeks, had approximately 1 week without PAL wear and then wore the second PAL for < or = 4 weeks. Eye and head movements were recorded at the beginning and end of each period of PAL wear in response to several visual tasks. Visual tasks were a flash discrimination task at 2 m and 40 cm, and reading text aloud. Quantitative analysis was undertaken for eye and head movement dynamics (latency, duration, peak velocity, etc.). Categorical analysis used eye and head movement metrics to classify participants as eye-movers, head-movers or mixed at each visit.
  
  
  RESULTS
  There was significant between-participant variability. A number of eye/head movement parameters exhibited carry-over effects. The number of vertical head movements for the distance task showed a significant increase between the first and second visit (F(1,9) = 5.578; p = 0.042), irrespective of lens design. Categorical analysis showed that participants employed task dependent strategies for all tasks. Participants that altered their strategy tended to include more head movements. Seven of the 10 participants preferred the second PAL worn.
  
  
  CONCLUSIONS
  Participants recruited more head movements for flash discrimination tasks and for reading text during adaptation to PAL wear. The many and various eye and head movement parameters analysed were unable to discriminate differences dependent on PAL design.
authors.affiliation: School of Optometry, University of Waterloo, Waterloo, ON, Canada. nhutchin@uwaterloo.ca
authors.forename: Natalie
authors.initials: N
authors.lastname: Hutchings
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Irving
authors.forename: Nadine
authors.initials: N
authors.lastname: Jung
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Dowling
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Wells
authors.forename: Linda
authors.initials: L
authors.lastname: Lillakas
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005133:Eye Movements / Q000502:physiology*; D005139:Eyeglasses; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015348:Vision, Binocular