The Influence of Part-time Patching Therapy on Types of Intermittent Exotropia

ABSTRACT

PURPOSE: To evaluate the influence of part-time patching therapy on the types of intermittent exotropia. METHODS: Forty-four children with basic type intermittent exotropia and 26 with convergence insufficiency type, aged 4 to 12 years, were evaluated. At initial examination, the deviating angles were obtained at distant and near with the alternate prism cover test after correcting for refractive errors. The types of intermittent exotropia were classified based on the reference values of distant-near difference as follow. In the patients with distant angle more than 30 PD, the reference value of distant-near difference was 10 PD, whereas in the patients with distance angle less than 30 PD, the value was one third of the distant angle. Three-hour per day patching of the non-deviating eye was performed for 3 months, and the change in the types of intermittent exotropia was investigated. RESULTS: At initial examination, mean deviating angles (PD) were 27.1 +/- 7.46 PD at distant, and 30.6 +/- 7.92 PD at near. After 3 months with 3-hours patching, the deviating angles were both reduced significantly to 25.9 +/- 9.10 PD at distant and 21.4 +/- 11.00 PD at near (p=0.005, <0.001 respectively). Fourteen patients (32%) of basic type were transformed to pseudodivergence excess type. Among the patients with basic type who showed no change in type, 9 (20%) showed a reduction of angles at both near and distant. Among the patients with convergence insufficiency type, 18 (69%) were converted to basic type and 2 (7%) to pseudodivergence excess type. CONCLUSIONS: Three-hour patching therapy converted the basic and convergence insufficiency type to the pseudodivergence excess and basic type in more than half of the intermittent exotropes.