Abstract
Purpose :
Children with amblyopia score lower on balance tasks using standardized tests of motor ability (Kelly et al, IOVS, 2020), and have ocular motor dysfunction such as fixation instability (Kelly et al, Exp Eye Res, 2018). Postural control during static balance is tightly linked to ocular motor control. Here, we examine the extent to which amblyopia impacts postural stability, and the contribution of ocular motor dysfunction to performance.
Methods :
Thirty children diagnosed with amblyopia and 32 control children ages 4 – 14 years were enrolled. Children were fitted with an iPod installed with the NIH Toolbox® Standing Balance Test that uses the built-in accelerometer to measure anterior-posterior (A-P) sway, and with a wearable eye tracker (Tobii Glasses 2) to record eye movements. Children completed 4-5 standing balance poses in sequential order; eyes open on flat surface, eyes closed on flat surface, eyes open on foam surface, eyes closed on foam surface, eyes open on flat surface with feet tandem (7+ years only). Children were instructed to stand as steady as possible for 50 seconds with feet together and arms crossed on the chest. For eyes-open poses, children were asked to stare at the center of a fixation cross. Outcome measures were overall A-P sway standard score, eyes open/eyes closed ratios (a measure of reliance on vision), and average fixation duration and total number of fixations during each eyes-open pose.
Results :
Compared with controls, amblyopic children had more A-P sway (amblyopia, 85±11 vs control, 91±9, p=0.024), and relied less on vision while standing on the flat surface (ratio, 1.15±0.31 vs 1.31±0.26, p=0.032) and foam surface (ratio, 1.33±0.30 vs 1.65±0.44, p=0.002). During all eyes-open poses, amblyopic children also had shorter average fixation duration (flat, 341±166 vs 656±529 msec, p=0.009; foam, 290±117 vs 483±327 msec, p=0.009; tandem, 309±139 vs 505±298 msec, p=0.023), and more fixations except for tandem (flat, 110±35 vs 79±39, p=0.004; foam, 123±32 vs 93±40, p=0.003; tandem, 96±37 vs 87±38, p=0.429) compared to controls.
Conclusions :
Postural stability during static balance is impacted by amblyopia. Further, these results indicate a role of ocular motor dysfunction in poor postural stability. Determining causes of poor balance may inform the development of interventions to help children with amblyopia succeed.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.