title: Effects of orthoptic treatment on the CA/C and AC/A ratios in convergence insufficiency.
abstract: OBJECTIVE
  To evaluate the effect of orthoptic treatment on the AC/A (A, accommodation; C, convergence) and CA/C ratios in subjects with convergence insufficiency (CI).
  
  
  METHODS
  The change in AC/A and CA/C ratios after a 12-week period of home-based orthoptic treatment was examined in 10 subjects (mean age, 25.4+/-4.1 years [SD]). Both the AC/A and CA/C ratios were measured by using gradient response methods. For the AC/A ratio, the gradient phoria method was used, and for the CA/C ratio the prism-induced change in accommodation was measured with a refractometer.
  
  
  RESULTS
  No change in the AC/A and CA/C ratios (P>0.05) were found after orthoptic treatment. However, improvements were found (P<0.05) in the fast and slow vergence mechanisms.
  
  
  CONCLUSIONS
  Despite improvements in the fast and slow vergence mechanisms no change was found in the AC/A and CA/C ratios after orthoptic treatment in CI subjects. This finding is unexpected in light of the present understanding of CI, and an alternative theory is proposed.
authors.affiliation: Binocular Research Lab, Unit of Optometry, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden. rlb@ste.ki.se
authors.forename: Rune L
authors.initials: RL
authors.lastname: Brautaset
authors.forename: Adrian J M
authors.initials: AJ
authors.lastname: Jennings
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000221:Adaptation, Ocular / Q000502:physiology; D000328:Adult; D003290:Convergence, Ocular / Q000502:physiology*; D005500:Follow-Up Studies; D006801:Humans; D015835:Ocular Motility Disorders / Q000503:physiopathology* / Q000628:therapy*; D009801:Oculomotor Muscles / Q000503:physiopathology; D009988:Orthoptics / Q000379:methods*; D015348:Vision, Binocular / Q000502:physiology