Convergence-accommodation is the synkinetic change in accommodation driven by vergence. A few studies have investigated the static and dynamic properties of this cross-link in adults but little is known about convergence-accommodation in children. The purpose of this study was to develop a technique for measuring convergence-accommodation and to study its dynamics (gain and movement time) in a sample of pre-school children.
Convergence-accommodation measures were examined on thiry-seven normal pre-school children (mean age = 4.0 ± 1.31 yrs). Stimulus CA/C (sCA/C) ratios and movement time measures of convergence-accommodation were assessed using a photorefractor while subjects viewed a DOG target. Repeated measures were obtained on eight normal adults (mean age = 23 ± 0.2 yrs).
The mean sCA/C ratios and movement times were not significantly different between adults and children (0.10 D/Δ [0.61 D/M.A.], 743 ± 70 ms and 0.11 D/Δ [0.50 D/M.A.], 787 ± 216 ms). Repeated measures on adults showed a non-significant mean difference of 0.001 D/Δ.
The results suggest that the possible differences in crystalline lens (plant) characteristics between children and adults do not appear to influence convergence-accommodation gain or duration.