Quantitative assessment of fixational saccades in school children. A new method

Abstract

PurposeTo develop and validate a technique for automatic analysis of fixational saccades in clincal practise, and to study age‐related changes in these parameters among normal children.MethodsThirty‐six normal children (19 boys and 17 girls, mean age = 9.8 years, range 5‐16 years) were examined. Eye movements were recorded during two repeated 30‐s fixation tasks from left eye with a video based eye‐tracking system (iView XTM High‐Speed, version 2.7.09 Senso Motoric Instruments, Berlin, Germany). Type). A special software programme was developed for the detection and quantification of fixational saccades including information about the length velocity and back shoot of the movements. The number of saccades within a 0.05‐degree amplitude intervals were plotted as a function of the amplitude and the plots were fitted to a biexponential function. The amplitude and number defining the maximum of this saccade distribution curve as well as the area under the curve (AUC) were calculated.ResultsThe total number of saccades per examination was 115.5 ± 71.3 (mean ± SD), range 14–276, which amounted to a total of 8315 saccades during the duplicate recordings from all 36 children. There was no correlation between age and the number of saccades per second (r2 = 0.07, p = 0.11), the number and amplitude of saccades at the maximum of the saccade distribution curve (r2 = 0.0002, p = 0.93) and (r2 = 0.002, p = 0.79), respectively, and the AUC (r2 = 0.09, p = 0.08).ConclusionsThe technique allows computerized quantification of small fixational eye movements and the extraction of measures of fixation in children that are independent of age. Studies of visual development using these parameters in children will not need a correction for age.