A prospective study of fusional convergence parameters in Chinese patients with intermittent exotropia

PURPOSE To evaluate the correlation between different fusional convergence parameters and the Newcastle Control Score (NCS) in children with intermittent exotropia. METHODS In this consecutive prospective observational series, 101 Chinese children with intermittent exotropia were examined by a single observer, who assessed the level of control using the revised NCS and measured the angle of deviation and fusional convergence. Levels of control were defined according to the NCS as good (0-3), moderate (4-6), or poor (7-9). The correlation between the different fusional convergence parameters and the NCS was evaluated. RESULTS The total convergence amplitude was similar among the different control groups (P = 0.288 and P = 0.628 at near and at distance, respectively). The convergence reserve was higher in the good control group compared with the moderate and poor control groups, both at near (P = 0.001) and at distance (P = 0.001). Among all fusional convergence parameters, we determined that the fusional reserve ratio had strongest correlation with control (near ratio: r = -0.66, P = 0.001; distant ratio: r = -0.59, P = 0.001). Among patients with a fusional reserve ratio >= 2 at distance, 100% (5 of 5 patients) of these patients demonstrated good control (NCS <= 3). CONCLUSIONS In children with intermittent exotropia, the total convergence amplitude was similar among different levels of control. The convergence reserve was lower in the poor control group. Fusional reserve ratio >= 2 was an indicator of good control in patients.