Surgical outcomes and etiological considerations in intermittent exotropia: a systematic narrative review

Introduction: Is Intermittent Exotropia being conceived and treated as an ocular-mechanical problem? Is etiology taken into account when planning for intervention? Which success criteria are used? Are they based on alignment or do they also consider visual function? In order to answer these questions, a review of studies assessing the outcomes of strabismus surgery in Intermittent Exotropia has been conducted. Methods: published between January 2003 and December 2023 were included. The database searched was MEDLINE following a predefined protocol. In addition to electronic database searches, manual searches were carried out and experts contacted. A total of 102 studies comprising 12 974 participants were included in this review. Results: Possible strabismus etiology was not stated in 91.2% of the studies. The underlying causes of the deviation were not taken into account for treatment consideration in any of the studies. Criteria for surgical success was based solely on ocular alignment (82.4%) and only 10 studies (9.8%) defined successful surgery with both motor and sensory criteria. Thirty-four different definitions of successful ocular alignment were identified. Discussion: In conclusion, Intermittent exotropia etiology is omitted in studies assessing surgical outcomes. The possible causes of the deviation are not taken into account when deciding on the type of surgery and are rarely mentioned. In most studies, the criteria for surgical success is based solely on eye alignment, independently of visual function and control.