Abstract
Purpose: :
The dynamic aspects of the accommodative response have been well documented in adults. This study utilized a movie stimulus in conjunction with dynamic IR photorefraction to measure accommodative lag and latency over a wide range of ages (preschool through adults) to better understand the changes in these responses as a function of age.
Methods: :
Accommodative (far to near) and disaccommodative (near to far) responses were measured dynamically using IR photrefraction as subjects viewed a movie stimulus alternating between 6m and 20cm at four second intervals. Measurements were recorded on 11 subjects between the ages of 3–29 years. Accommodative latency was the time from onset of the near stimulus to initiation of the accommodative response. Disaccommodative latency was the time from onset of the far stimulus to initiation of the disaccommodative response. Mean lag was the mean difference between stimulus demand and accommodative response for the interval between 1 and 3 seconds after initiation of the accommodative response.
Results: :
The mean accommodative latencies for children (3–13 years) were longer than for adults (19–29 yrs); 364 ±93ms vs 283 ±30ms, and the difference was statistically significant (unpooled t–test, p < 0.03). Disaccommodative latencies were also longer in children than adults; 443 ±128ms vs 233 ±33ms, and the difference was statistically significant (unpooled t test, p < 0.002). Mean lag measurements were smaller in younger children (3–8 yrs) than in older children and adults (12–29 yrs); 2.48 ±0.47D vs 3.12 ±0.13D. This difference also reached statistical significance with the unpooled t–test (p < 0.01). There was greater variability in mean lag among younger children (3–8 yrs) than older children and adults (12–29 yrs) (F–test, p < 0.02).
Conclusions: :
With increasing age accommodative and disaccommodative latencies become shorter. Mean lag shows more variability between individuals at young ages and becomes less variable with increasing age, as well as increases in magnitude. These data suggest that aspects of accommodation continue to develop through childhood.