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Joost Felius, Richard W. Hertle, Jingyun Wang, Vidhya Subramanian, Reed M. Jost, Priscilla M. Berry, Eileen E. Birch; Ocular Motor Analysis of Monocular Visual Preference in Children with Amblyopia. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4690.
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© ARVO (1962-2015); The Authors (2016-present)
Timely detection of amblyopia in preverbal children is hampered by the limited sensitivity of grating acuity and fixation preference testing. We evaluated eye movement recordings (EMRs) as a potential efferent system outcome for young children with interocular asymmetry in the afferent visual system, and to assess whether visual acuity asymmetries are reflected in asymmetric monocular EMR outcomes.
EMRs (sampling rate 500 Hz; EyeLink1000 or Ober2) were obtained during binocular and monocular fixation from 22 children, age ≥5 years, with amblyopia (9 anisometropic, 5 strabismic, 8 combined mechanism.) Monocular best-corrected visual acuity was tested in each eye. Qualitative and quantitative analyses of EMRs were assessed in terms of waveforms and oscillation frequency, and compared to the interocular difference (IOD) in visual acuity.
Of the 22 children (mean IOD=0.4±0.2 logMAR), 19 (86%) showed ocular motor dysfunction. Most (n=18) showed pathologic square-wave oscillations (SOs), while fewer had waveforms typical of infantile (n=3) or fusion maldevelopment (n=5) nystagmus syndromes. However, the overall presence of abnormalities was not associated with IOD and some of the ‘deeper’ amblyopes did not show abnormalities in waveform or frequency. The 19 with EMR abnormalities all showed interocular asymmetry in waveform and/or oscillation frequency, and in all cases the least severe ocular motor dysfunction was found in the better seeing eye. The presence of interocular SO asymmetry was associated with IOD (t=2.5, P<0.001). No effects of the type of amblyopia were found (P>0.2).
Asymmetric ocular motor abnormalities, most prominently SOs, are common in children with amblyopia. In those with EMR abnormalities, we found 100% concordance between ‘eye with better eye movements’ and ‘eye with better visual acuity’. The presence of asymmetric SOs in amblyopia may reflect a poor coupling of the monocular sensory-motor calibration during a sensitive period of visual development. EMRs appear to be a valid ‘motor’ approach to assessing ‘sensory’ preference in amblyopia, which may be useful in preverbal children. Refining the choice of EMR parameters may result in a better association of the ocular motor outcome and the depth of amblyopia.
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