title: Preoperative factors predicting the surgical response of bilateral lateral rectus recession surgery in patients with infantile exotropia.
abstract: OBJECTIVE
  To determine the preoperative factors affecting the efficacy in bilateral lateral rectus recession surgery for infantile exotropia.
  
  
  METHODS
  This was a retrospective study of 50 patients with infantile exotropia who had bilateral lateral rectus recession surgery correction with more than 1 year of follow-up. Preoperative parameters influencing the response of the surgery were obtained and evaluated using multiple regression analysis including age at onset, age at surgery, interval between onset and surgery, preoperative deviation, refractive error, anisometropia, amount of surgery performed, presence of A- or V-pattern, and preoperative phase of exotropia. The response to surgery was defined as the change in deviation divided by the amount of the surgery.
  
  
  RESULTS
  Thirty-two (64%) and 24 (48%) patients had successful outcome at 6 weeks and 1 year postoperatively, respectively. The mean response to surgery was 1.79 ± 0.63 prism diopters (PD)/mm recession at 6 weeks and 1.58 ± 0.75 PD/mm recession at 1 year postoperatively. Exotropic drift was 5.12 ± 7.27 PD at 6 weeks and 8.02 ± 6.81 PD at 1 year postoperatively. Pre-operative deviation was correlated with the response of surgery at 6 weeks (β = 0.342, P = .020) and 1 year (β = 0.391, P = .007) postoperatively.
  
  
  CONCLUSIONS
  Surgical response decreases over time due to the exotropic drift. Larger preoperative distance deviation was associated with larger surgical response. Both the exotropic drift and the preoperative deviation should be considered in applying the surgical dose in infantile exotropia.
authors.affiliation: Department of Ophthalmology, Tung Wah Eastern Hospital, Hong Kong. yamcheuksing@gmail.com
authors.forename: Jason C S
authors.initials: JC
authors.lastname: Yam
authors.forename: Gabriela S L
authors.initials: GS
authors.lastname: Chong
authors.forename: Patrick K W
authors.initials: PK
authors.lastname: Wu
authors.forename: Ursula S F
authors.initials: US
authors.lastname: Wong
authors.forename: Clement W N
authors.initials: CW
authors.lastname: Chan
authors.forename: Simon T C
authors.initials: ST
authors.lastname: Ko
mesh_terms: D017668:Age of Onset; D002675:Child, Preschool; D005099:Exotropia / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D008297:Male; D009801:Oculomotor Muscles / Q000601:surgery*; D013508:Ophthalmologic Surgical Procedures; D057234:Preoperative Period; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome