Normative Fusional Vergence in Pediatric Intermittent Exotropia Using Synoptophore and Step Vergence Methods

Purpose: The purpose of this study is to establish normative fusional vergence (FV) amplitudes in children with intermittent exotropia (IXT) utilizing synoptophore and step vergence (prism bar) methods and compare measurements. Methods: This prospective study investigated 98 children aged 6 to 16 years diagnosed with IXT. The synoptophore and prism bar step vergence procedures were used to assess PFV and NFV at 33 cm and 6 m fixation. We wrote down the test break, and recovery points. Paired t-tests were performed to compare the two techniques. Results: Synoptophore outperformed step vergence in both near and distance fixation, with significantly higher PFV break and recovery values (break: 23.3 ± 12.4 vs 15.8 ± 11.2 prism diopters [PD]; recovery: 14.6 ± 11.3 vs 8.9 ± 8.5 PD; P < 0.0001) and 17.0 ± 11.3 vs 11.0 ± 8.3 PD; recovery: 8.8 ± 10.0 vs 6.2 ± 6.8 PD; Near NFV break levels were comparable (P = 0.387), whereas step vergence led to larger recovery (10.9 ± 6.7 vs 7.4 ± 5.9 PD; P = 0.00014).