title: Intermittent exotropia: facts, opinions, and unknowns.
abstract: BACKGROUND
  Intermittent exotropia (IXT) can be a controversial topic, often eliciting lively discussion. This lecture will discuss its definition, incidence, age of onset, presentation, natural variation, criteria for deterioration, goals of treatment, effectiveness of surgical treatment, types of surgical treatment, and unwanted effects of surgical treatment.
  
  
  METHODS
  Results from the scientific literature, opinions of respected colleagues, the opinion of the author, and the results of live polling of the audience during the John Pratt-Johnson lecture are presented.
  
  
  RESULTS
  IXT is defined as an exotropia that is present intermittently predominantly for distance. Its incidence is about 1% and it usually has an onset before age 5. Patients often present because of concern regarding the appearance of the eye misalignment. There is natural variation in the control of IXT, the angle of IXT, and the amount of stereopsis. Criteria that denote deterioration are increasing frequency of IXT, progressively and consistently increasing angle of IXT, loss of binocular vision, and increasing concern regarding the patient's appearance and its effect on social interaction. Goals of treatment are to retain equal or nearly equal vision, to obtain acceptable cosmesis, and to retain binocular vision. The long-term success of surgical treatment is not well proven. Persistent postoperative overcorrection is an unwanted effect of surgical treatment.
  
  
  CONCLUSIONS
  The inherent biologic variation that occurs when measuring the components of IXT makes it difficult to be dogmatic about IXT, particularly when trying to decide when deterioration is occurring.
authors.affiliation: Division of Ophthalmology, Department of Surgery, University of Calgary, Alberta, Canada.
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Romanchuk
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology; D003290:Convergence, Ocular / Q000502:physiology; D003867:Depth Perception / Q000502:physiology; D005099:Exotropia / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D009801:Oculomotor Muscles / Q000503:physiopathology / Q000601:surgery; D013508:Ophthalmologic Surgical Procedures; D015348:Vision, Binocular / Q000502:physiology