Maintenance of normal fusion in intermittent exotropia

Purpose To evaluate the reliability of the Bagolini filter bar and striated lenses for measuring the fusion maintenance score, which is the ability of participants with intermittent exotropia to maintain normal sensorimotor fusion. Methods Thirty‐two Chinese participants aged 7–20 years with intermittent exotropia (excluding the convergence insufficiency type) were enrolled in this prospective study. At the eligibility screening, visual acuity, cover test and assessment of the office control score were performed. At study visit 1, eligible participants underwent negative and positive fusional vergence tests at far and near, eye dominance test and the fusion maintenance test. All eligible participants returned for study visit 2 on the same day (2–4 h later) and the testing was repeated. The primary outcome measure was the intra‐class correlation coefficient of the fusion maintenance score between the two study visits. Results The intra‐class correlation coefficient of the fusion maintenance score was 0.84, indicating good reliability. There was no significant difference (mean difference = 0.05, p = 0.95) between the fusion maintenance scores for the first (5.62) and second study visits (5.57). The coefficient of repeatability and the smallest detectable change for the fusion maintenance scores were 7.6 and 6.3, respectively. The fusion maintenance score was significantly associated with the distance (Spearman correlation −0.57, p