Development of visual pursuit in the first 6 years of life

Abstract

There are few previous investigations on the development of smooth visual pursuit in children. The aim of this study was to determine normative values for the development of horizontal and vertical smooth pursuit in a large number of normal children. Eye movements of 358 healthy children aged 6 weeks through 6 years were recorded using infrared photo-oculography. Visual pursuit was elicited with colored squares of 1.2 degrees of visual angle. The stimulus moved horizontally or vertically with constant velocities of 7.5, 15, or 30 degrees/s. Attention time increased with increasing age from 0.54 to 0.77 (P<0.01) and decreased with increasing stimulus velocities (P<0.01). The ratio of time of smooth pursuit to time of smooth pursuit plus saccades increased with increasing age from 0.63 to 0.78 (P<0.01) and decreased with increasing stimulus velocities (P<0.01). For stimulus velocities of 7.5 degrees/s, no significant difference was found between horizontal and vertical gain values. For stimulus velocities of 15 degrees/s and 30 degrees/s, gains for horizontal movements were larger that for vertical (P<0.05). Increasing stimulus speeds were associated with decreasing gains (P<0.05). This study provides the following normative values for photo-oculography in healthy children aged 6 weeks through 6 years of age: attention time, smooth pursuit time, and gain for three stimulus velocities presented horizontally and vertically. This normative database should help to diagnose pathologic ophthalmological or neuropediatric conditions, to perform screening interventions, and to initiate therapies.