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Joost Felius, Reed M. Jost, David R. Stager, Sr., Vidhya Subramanian; Interocular Asymmetries In Square-wave Oscillations In Children With Amblyopia. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3898.
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© ARVO (1962-2015); The Authors (2016-present)
We recently explored interocular asymmetries in eye movement abnormalities in children with amblyopia. In particular, we found square-wave oscillations (SOs) to be more prevalent when viewing with the amblyopic eye compared to viewing with the non-amblyopic eye (Felius et al., ARVO, 2011). Here we present a more formal analysis of similar data to quantify interocular SO asymmetries in amblyopia in terms of rate, ampitude and duration.
Eye movement recordings were obtained at 500 Hz from 18 children with mild to moderate amblyopia associated with strabismus and/or anisometropia (visual acuity, 0.2 - 0.8 logMAR; age, 8.8±3.1 years) and 5 age-similar normals, monocularly viewing a steady target. Data were analyzed using saccade detection software and a decision algorithm based on the likelihood of each pair of saccades forming an SO taking into account intersaccadic intervals and similarities in size and direction (adapted from Otero-Millan et al., J Neurosci, 2011).
The mean rate of SOs was greater in children with amblyopia (8.7±5.8 min-1) than in normals (2.2±2.6 min-1) (P=0.002). On average SOs were more frequent (11.6±8.4 min-1 vs 5.8±5.7 min-1; P=0.008) and larger (1.0°±0.4° vs 0.7°±0.4°; P=0.04) when viewing with the amblyopic eye compared to viewing with the non-amblyopic eye, but similar in duration (360±74 ms vs 426±178 ms; P=0.3). In 15 patients (83%), viewing with the amblyopic eye resulted in a greater rate of SOs, yet there was no significant association between SO characteristics and visual acuity across patients (P>0.2).
These results confirm the presence of larger and more frequent SOs when viewing with the amblyopic eye. Timely diagnosis of amblyopia is important, yet, in preverbal children it is hampered by the limited sensitivity of grating acuity and fixation preference testing. The finding of interocular asymmetries in SO characteristics in many amblyopes, even in those with mild amblyopia, may hold promise for objective detection of amblyopia.
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