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Dorte A. Larsen, Toke Bek; No Age-dependent Variation In Amplitude And Velocity Of Fixation Saccades In Children Older Than Five Years. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4863.
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Fixation saccades are believed to play a critical role in maintaining visual acuity by avoiding a stabilized image on the retina. Fixation saccades are altered in diseases that affect visual acuity, but data from normal persons are necessary for the monitoring of pathological changes in visual function. Previous studies have shown a linear relation between the amplitude and velocity of fixation saccades in adults, but it is unknown whether this relation is also present in children. Therefore, the purpose was to study the relation between amplitude and velocity of fixation saccades in children of school age.
Ten healthy children (mean age 8.8 years, range 5-15 years; 5 boys, 5 girls) with visual acuity of 1.0 and no history of ocular disease, were examined. Fixation movements were recorded using a video based eye-tracking system (Senso Motoric type iView X Hi-Speed, Berlin, Germany) using a sampling rate of 500 Hz during 25 seconds. Fixation saccades were identified as movements with an amplitude between 0.22-1.09 degrees, a minimum velocity of 5 deg/s, and having overshoot. For each child, the amplitude of fixation saccades was plotted as a function of velocity, and the slope of the best fitting line curve was calculated. Finally, for all test persons, the slope was plotted as a function of the age of the child.
Two hundred and fifty two fixation saccades were detected in the studied children, corresponding to a mean frequency of 0.504 Hz, range 0.28-0.84 Hz. The mean amplitude was 0.54 deg, range 0.22-1.09 deg, and the mean velocity was 32.8 deg/s, range 9.1-166.6 deg/s. There was no significant correlation between age and velocity/amplitude curve, (r2=0,39, p= 0.05)
The amplitude and velocity of fixation saccades do not correlate with age in children between five and fifteen years of age. Clinical studies of fixation saccades in children of this age group need not introduce corrections for variation with age.
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