title: Accommodation steps, target spatial frequency and refractive error.
abstract: OBJECTIVE
  Errors in the accommodation response of myopes have been reported in many studies although questions remain about the exact differences in accommodation steps when compared with emmetropic individuals.
  
  
  METHODS
  The characteristics of the accommodation step response to large (4/1D) and small (3/2D) steps in targets with low (0.5 cpd), mid (4 cpd) and high (16 cpd) spatial frequency (SF) information was measured in myopes (MYOs) and emmetropes (EMMs).
  
  
  RESULTS
  In terms of step size, the larger steps showed a greater response in the 4 cpd condition than the 0.5 and 16 cpd conditions and an improved percentage correct response in the 4 cpd compared to the 16 cpd steps. In small step conditions target SF had less effect upon the magnitude of the response. In terms of refractive group differences, MYOs had a lower proportion of correct accommodation responses compared to EMMs during the small steps only, however, when correct steps were performed there were no differences in the characteristics of both large and small step responses between MYOs and EMMs.
  
  
  CONCLUSIONS
  These findings suggest that MYOs have some difficulty interpreting small changes in defocus to initiate or possibly fine tune a small accommodation response, however, when a correct accommodation step response is made, the MYOs accommodation plant responds in a similar manner to EMMs.
authors.affiliation: Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK.
authors.forename: Niall C
authors.initials: NC
authors.lastname: Strang
authors.forename: Mhairi
authors.initials: M
authors.lastname: Day
authors.forename: Lyle S
authors.initials: LS
authors.lastname: Gray
authors.forename: Dirk
authors.initials: D
authors.lastname: Seidel
mesh_terms: D000065:Accommodation, Ocular; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000503:physiopathology*; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation / Q000009:adverse effects* / Q000379:methods; D012030:Refractive Errors / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D055815:Young Adult