Abstract
Purpose :
In adult with intermittent exotropia (IXT), spontaneous saccades are reported to have increased peak velocity (PV). This observation raises a question: Do patients with IXT exhibit these characteristics from childhood, or do they develop in conjunction with the pathogenesis of IXT? To investigate this, we compared the PV and gain of spontaneous saccades between children with IXT and age-matched children without strabismus in a simple saccade task.
Methods :
Participants aged ≦ 12 years were divided into two groups: patients with IXT who had no history of strabismus surgery (IXT group) and normal children without strabismus (no strabismus group). At the start of the test trial, they were instructed to fixate their gaze on a centrally located target under binocular viewing. Upon the appearance of a new target, randomly positioned either 18.3° to the right or left, participants were asked to shift their gaze to this target as quickly as possible. Horizontal saccades were recorded using a video eye-tracker, and the PV and gain of the initial saccades were calculated. The asymmetry of adduction-abduction gain for each saccade and the differences in saccade gain between the right and left eyes, indicating binocular coordination; these aspects were compared between the IXT and no strabismus groups.
Results :
The study included 39 children with IXT (mean age: 8.9 ± 2.2 years) and 10 normal children (mean age: 7.9 ± 2.4 years). In the IXT group, the deviation angle was 30.3 ± 13.5 prism diopters at near and 30.6 ± 10.5 prism diopters at distance, and stereopsis was < 60 arc-seconds in 29 patients and 80−400 arc-seconds in 10 patients. When comparing horizontal saccades in all directions between the IXT and no strabismus groups, no significant difference were found in either saccade PV or gain between the two groups. However, in the IXT group, there was a tendency for higher PV and gain in adduction saccades compared to abduction saccades, although this difference was not significant. In the normal group, a similar trend was observed, more pronounced in the dominant eye, and the difference was significant.
Conclusions :
The PV and gain of saccade in children aged 4−12 years were not significantly different between IXT group and normal group, unlike in adults. In addition, although both groups exhibited dominance in adduction during saccade, the dominance was less pronounced in children with IXT.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.