The position of eye and head for measurement of lateral incomitancy in intermittent exotropes

ABSTRACT

PURPOSE: To determine proper position of lateral gazes and angle of head turn for the measuring lateral incomitancy in intermittent exotropia. METHODS: Twenty-five Korean intermittent exotropes with exoangle more than 25 prism diopters (PD) and 25 orthophoric people were taken. Three lateral gazes were proposed: position A, when the lateral limbus of the abducted eye was off the lateral canthus; position B, when touched the lateral canthus; and position C when was hidden behind the lateral canthus. The angle of deviation and head turn were measured at each position. In the most comfortable position which subjects selected, the length from lateral canthus to lateral limbus (lateral cantho-limbal distance) of the abducted eye was measured. RESULTS: 23 patients of each group selected that position A was the most comfortable. At position A, the mean of cantho-limbal distance in exotropes was 1.19mm at the right lateral gaze and 1.04 mm at left, people with orthophoria showed larger values in both gazes. The average amount of head turn was 24.1 degrees at the right lateral gaze and 24.3 degrees at the left at position A, 27.5 degrees and 34.1 degrees at position B, 27.6 degrees and 33.7degrees at position C. The average angle of exodeviation was 27.4 PD in the primary gaze. It was 21.7 PD in the right lateral gaze and 20.3 PD in the left lateral gaze at position A, 17.9 PD and 17.5 PD at position B, and 9.0 PD and 8.6 PD at position C. CONCLUSIONS: In the measurement of lateral exo-angle to evaluate lateral incomitancy in intermittent exotropia, the most appropriate position of eye and head turn turned to be when the lateral limbus of the abducted eye is about 1mm apart from the lateral canthus with head turn of 25degrees laterally.