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H. A. Anderson, A. Glasser, R. E. Manny; Dynamic Measures of Accommodation in Individuals With Down Syndrome. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2797.
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© ARVO (1962-2015); The Authors (2016-present)
Studies measuring static aspects of accommodation have shown individuals with Down syndrome (DS) have high accommodative lags. In this study dynamic measures of accommodation were explored to determine if additional aspects of accommodation are affected in DS.
Accommodative responses were recorded dynamically at 30 Hz with an infrared photorefractor as subjects viewed a movie stimulus monocularly (OS). The stimulus alternated step-wise between far (0D) and near demands (2, 3, 4, or 5D). Accommodative and disaccommodative latencies, peak velocities, and the RMS deviation of accommodative microfluctuations for sustained near responses were determined. 50 control subjects without DS (3 to 38 years, BVA 20/20) and 33 individuals with DS (3-39 years, BVA range 20/25 to 20/100) were recruited to compare the two populations.
41 controls and 18 subjects with DS had photorefraction recordings suitable for inclusion in analysis. Median accommodative responses were significantly lower in subjects with DS than controls for each demand (p ≤ 0.0056). Median accommodative latencies were significantly longer in subjects with DS than controls for the 3 and 4 D demands (Mann-Whitney Test: p ≤ 0.0019), but disaccommodative latencies did not differ significantly between the two groups. Accommodative and disaccommodative peak velocities were similar between both populations, although comparisons were limited to responses up to 2.5 D due the reduced magnitude of accommodative responses in subjects with DS. There was a significant linear increase in RMS of accommodative microfluctuations with increasing response amplitude for both populations (p ≤ 0.001), although the magnitude of the RMS was significantly greater in subjects with DS than controls (one-way ANCOVA, F=30.11, df = 1,520, p<0.0001).
Peak velocities of accommodation and disaccommodation (motor aspects of accommodation) for low response amplitudes did not differ between controls and subjects with DS; however, accommodative latencies (sensory and motor) and microfluctuations (sensory and motor) were poorer in subjects with DS. These results suggest that sensory aspects of accommodation are deficient in DS, while purely motor aspects are unaffected.
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