Surgical Planning for Pattern Strabismus in Patients with Intermittent Exotropia: Evaluating Techniques and Outcomes

Abstract

<i>Background or purpose</i>: Intermittent exotropia is the most common cause of divergent deviation. Pattern strabismus may coexist with horizontal deviations in up 35% of cases. Managing pattern strabismus concomitantly with the correction of horizontal strabismus poses a challenge due to imbalances in force vectors. This study aims to evaluate the effects of planning an intermittent exotropia surgery considering the presence of pattern strabismus and its surgical resolution. <i>Methods</i>: Observational retrospective study of patients with intermittent exotropia who underwent surgical correction at center between 2017 and 2022. Patients were categorized by the presence of pattern strabismus and furthermore by surgical technique for the correction of said incomitance (weakening of inferior oblique muscles or vertical transposition of lateral rectus muscles). Outcomes of post-surgical horizontal deviation and presence of postoperative pattern strabismus were statistical analyzed between groups using SPSS software v28.0. A p-value <0,05 was considered significant. <i>Results</i>: A total of 169 patients had surgical correction for intermittent exotropia. Pattern strabismus was observed in 35,5% of patients, primarily V-pattern (88,3%). Most were male (58, 35%) with mean age of 15,13±16,38 years. 41,7% patients with pattern strabismus underwent correction of the incomitance. All techniques showed significant reduction of horizontal near (p<0,001) and distance (p<0,001) deviation. However, incomitance correction favored strongly not only the collapsing of pattern strabismus (p=0,027) but also achieved better results in postoperative distance (p=0,002) and near (p=0,031) horizontal deviation. The two techniques for resolution of pattern strabismus showed comparable results in postoperative horizontal near deviation values and resolution of pattern strabismus, favoring vertical transposition in horizontal distance deviation values (p=0,015). <i>Conclusions</i>: The presence of pattern deviations should be actively persecuted in pre-operatively appointments to plan the surgery appropriately, as benefits in correcting the vertical incomitance are supported by this study findings. Both vertical transposition of lateral rectus muscles and weakening of inferior oblique muscles are effective techniques to correct vertical incomitances.