The effect of flicker rate on nasal and temporal measured visual field extent in infants

Purpose. To explore the effect of peripheral stimulus flicker rate on measured visual field extent (MVFE) in young infants. Methods. Three hundred sixty infants (180 each at 3.5 and 7 months of age) were tested monocularly with a light-emitting diode static perimetry procedure using a double-arc perimeter with arms at 45°, 135°, 225°, and 315°. Each subject was tested with one of six flicker conditions: no flicker, 1 Hz, 3 Hz, 10 Hz, 20 Hz, and 40 Hz. An interpolated estimate of the location at which 50% of subjects detected the peripheral stimulus (corrected for spontaneous eye movements) and the mean location of the farthest spot seen were calculated across subjects for each perimeter arm for each flicker condition for each age group. Results. Nasally, MVFE was larger for 7-month-old than for 3.5-month-old infants. Across both ages, infants showed larger MVFE for 10-Hz stimuli than for nonflickering stimuli, but MVFE did not differ between any other flicker conditions. Temporally, response to flicker varied with age. For 3.5-month-old infants, MVFE was smaller for the no flicker condition than for the 3-Hz, 10-Hz, and 20-Hz conditions, but there were no other differences across flicker conditions. For 7-month-old infants, MVFE was larger for 3-Hz stimuli than for the no flicker, 1-Hz, 20-Hz, and 40-Hz conditions, but there were no other differences across flicker conditions. Additional analyses showed that the effect of flicker rate on the percentage of subjects looking at a peripheral stimulus at a single eccentricity (29°) was similar to the effect of stimulus flicker across eccentricities, as reflected in MVFE. Conclusions. Peripheral stimulus flicker can enhance the MVFE in 3.5- and 7-month-old infants. However, the effect depends on flicker rate and is consistent with previous data indicating that 10 Hz and perhaps 3 Hz are especially effective in enhancing MVFE in older infants and young children.