The Newcastle Control Score: a new method of grading the severity of intermittent distance exotropia.

AIM To describe the development and application of a novel scoring system for grading the severity of intermittent distance exotropia (IDEX) and its potential application as an intervention criterion for surgical intervention. METHODS The Newcastle Control Score (NCS) for IDEX was developed by incorporating both subjective (home control) and objective (clinic control) criteria into a scale to grade severity. The score structure described was evaluated for interobserver and test-retest reliability. To determine an optimal score threshold for surgical intervention, 170 cases of IDEX were scored retrospectively. Cure rates for surgical and non-surgical cases were then compared according to preoperative or presenting scores. RESULTS Interobserver and test-test reliability were good (r = 0.82 and r = 0.89 respectively). Total cure rate with surgery was 54% and without surgery 18% (chi(2) = 23.093, df = 1, p<0.001). Significantly fewer patients with NCS >/=3 achieved cure without surgery than those with NCS 2 (chi(2) = 3.362, df = 1, p<0.047). CONCLUSIONS The NCS is a reliable method for grading the severity of IDEX and aids decisions regarding intervention. Patients with a score of 3 or more are unlikely to attain a cure without surgery.