title: Changes in stimulus and response AC/A ratio with vision therapy in Convergence Insufficiency.
abstract: OBJECTIVE
  To evaluate the changes in the stimulus and response Accommodative Convergence to Accommodation (AC/A) ratio following vision therapy (VT) in Convergence Insufficiency (CI).
  
  
  METHODS
  Stimulus and response AC/A ratio were measured on twenty five CI participants, pre and post 10 sessions of VT. Stimulus AC/A ratio was measured using the gradient method and response AC/A ratio was calculated using modified Thorington technique with accommodative responses measured using WAM-5500 open-field autorefractor. The gradient stimulus and response AC/A cross-link ratios were compared with thirty age matched controls.
  
  
  RESULTS
  Mean age of the CI and control participants were 23.3±5.2 years and 22.7±4.2 years, respectively. The mean stimulus and response AC/A ratio for CI pre therapy was 2.2±0.72 and 6.3±2.0 PD/D that changed to 4.2±0.9 and 8.28±3.31 PD/D respectively post vision therapy and these changes were statistically significant (paired t-test; p<0.001). The mean stimulus and response AC/A ratio for controls was 3.1±0.81 and 8.95±2.5 PD/D respectively.
  
  
  CONCLUSIONS
  Stimulus and response AC/A ratio increased following VT, accompanied by clinically significant changes in vergence and accommodation parameters in subjects with convergence insufficiency. This represents the plasticity of the AC/A crosslink ratios that could be achieved with vision therapy in CI.
authors.affiliation: Srimathi Sundari Subramanian Department of Visual Psychophysics, Elite School of Optometry, Chennai, India(1).
authors.forename: Neeraj Kumar
authors.initials: NK
authors.lastname: Singh
authors.affiliation: Binocular Vision and Vision Therapy Clinic, Sankara Nethralaya, Chennai, India.
authors.forename: Revathy
authors.initials: R
authors.lastname: Mani
authors.affiliation: Srimathi Sundari Subramanian Department of Visual Psychophysics, Elite School of Optometry, Chennai, India(1); Binocular Vision and Vision Therapy Clinic, Sankara Nethralaya, Chennai, India. Electronic address: rizwana@snmail.org.
authors.forename: Jameel Rizwana
authors.initials: JR
authors.lastname: Hussaindeen
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D002648:Child; D003290:Convergence, Ocular / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D015835:Ocular Motility Disorders / Q000503:physiopathology / Q000628:therapy*; D009907:Optometry / Q000379:methods*; D010775:Photic Stimulation / Q000379:methods; D014792:Visual Acuity; D055815:Young Adult
keywords: Accommodative convergence to accommodation ratio; Convergence Insufficiency; Insuficiencia de Convergencia; Relación acomodación/convergencia acomodativa (AC/A); Terapia visual; Vision therapy