Abstract
Abstract: :
Purpose: To determine the effect of peripheral stimulus flicker rate on measured visual field extent (MVFE) in young children. Method: Binocular visual field extent was measured in 90 full-term 2.5-year-old children in one study (Delaney et al, in press) and 120 full-term 2.5-year-old children in a second study, using a double-arc perimeter with arms oriented at 45º,135º, 225º, and 315º. The central stimulus was a ring of 8 yellow 1º-diameter lights illuminated pairwise and sequentially between peripheral stimulus presentations. Peripheral stimuli were 3º yellow LEDs located along the perimeter arms at eccentricities of 100º, 80º, 59º, and 39º. Six rates of peripheral stimulus flicker were used (0 Hz, 3 Hz, and 10 Hz, in the first study and 1 Hz, 10 Hz, 20 Hz, and 40 Hz in the second). Each child completed 16 trials (4 locations per arm) at one of the flicker rates. Testing was conducted using a static perimetry procedure in which an observer, who was masked to peripheral stimulus location and flicker rate, judged the direction of the child's first eye movement away from center. Data were scored as the farthest spot seen by each subject along each arm. The MVFE for the 10 Hz condition did not differ significantly for the two studies (F(1,58)=1.458, p≷0.2), therefore the results of the two studies have been combined. Results: Mean MVFE was 60.59º (sd=12.69) for the 0 Hz; 67.03º (sd=9.72) for the 1 Hz; 70.26º (sd=10.11) for the 3 Hz; 73.37º (sd=11.30) for the 10Hz; 66.86º (sd=10.43) for the 20 Hz; and 62.45º (sd=14.38) for the 40 Hz stimulus flicker rate. The MVFE for the 3 Hz and 10 Hz flicker rates differed significantly from the MVFE found for the 0 Hz flicker rate. The difference in MFVE for the 10 Hz and 40 Hz flicker rates was also significant (all p's<0.05 after Bonferroni correction). Conclusion: In 2.5-year-olds, binocular MVFE is significantly influenced by stimulus flicker rate. MVFE increased from 60.59º to 73.37º as flicker rate increased from 0 to 10 Hz and decreased from 73.37º to 62.45º as flicker rate increased from 10 Hz to 40 Hz. Further research is being conducted to determine whether this pattern of results changes with age.
Keywords: 624 visual fields • 511 perimetry • 623 visual development: infancy and childhood