title: Effect of defocus on response time in different age groups: A pilot study.
abstract: OBJECTIVE
  To assess the response time associated with visual performance (VP) tasks in the presence of defocus in different presbyopic populations.
  
  
  METHODS
  58 eyes between the ages of 35 and 50 years were studied. Subjects were categorized as pre-presbyopic (35-39 years), early-presbyopic (40-45 years), and mid-presbyopic (46-50 years). VP measurements obtained monocularly included distance and near high contrast (HC) and low contrast (LC) optotype recognition, and contrast threshold at 12cpd for different defocus magnitudes between 0D and 3D in 1D steps. Response time defined as the time taken to recognize and verbalize an optotype, was compared among different presbyopic age groups.
  
  
  RESULTS
  From 58 eyes, mean (SD) response time for high contrast distance visual acuity for 0D through 3D ranged between 1.48 (0.23) and 1.87 (0.31)s, whereas low contrast distance visual acuity ranged between 1.5 (0.22) and 2.09 (0.49)s. Mean response time for high contrast near visual acuity for 0D through 3D ranged between 1.56 (0.19) and 2.23 (0.45)s. However, for low contrast near visual acuity it ranged between 1.75 (0.32) and 2.71 (0.94)s. Mean (SD) response time for 12cpd ranged between 2.11 (0.50) and 5.72 (1.09)s. ANOVA revealed a significant difference in response time for distance, near visual acuity and contrast sensitivity as a function of defocus for different age groups.
  
  
  CONCLUSIONS
  Response time is increased in the presence of increasing defocus for both distance and near visual acuity and could impact on performance for critical tasks. Full correction of visual acuity at distance and near in presbyopes is warranted always.
authors.affiliation: College of Optometry, Midwestern University, Glendale, AZ 85308, USA. Electronic address: bvasud@midwestern.edu.
authors.forename: Balamurali
authors.initials: B
authors.lastname: Vasudevan
authors.affiliation: College of Optometry, Midwestern University, Glendale, AZ 85308, USA.
authors.forename: Kaiser
authors.initials: K
authors.lastname: Sultani
authors.affiliation: College of Optometry, Midwestern University, Glendale, AZ 85308, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Cossette
authors.affiliation: College of Optometry, Midwestern University, Glendale, AZ 85308, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Burr
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology; D010865:Pilot Projects; D011305:Presbyopia / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D012684:Sensory Thresholds / Q000502:physiology; D015349:Vision, Monocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology
keywords: Defocus; Desenfoque; Presbicia; Presbyopia; Reaction time; Tiempo de reacción