Minus lens stimulated accommodative lag as a function of age

Abstract

Purpose: Previous studies in children report reduced accommodative responses with minus lens-stimulated demands compared with proximal demands. This study seeks to identify age-related changes in accommodative lag with minus lens-stimulated demands in subjects from preschoolers to adults.

Methods: Accommodative responses were measured in 101 subjects (3 to 40 years) with at least 10 subjects in each 5-year age bin. Subjects monocularly viewed a high-contrast target at 33.3 cm on the near-point rod of the Grand Seiko autorefractor. Measurements of refraction were taken as the subject viewed the target. Accommodative lag was defined as the difference between demand and measured response. Four additional demands were tested by introducing minus lenses [-1 to -4 diopter (D)] in the spectacle plane of the viewing eye. Maximum accommodative amplitudes were determined by presenting additional lenses until the measured response plateaued or peaked. Accommodative demands and responses were adjusted to the corneal plane. RESULTS.: Accommodative lag showed a significant linear decrease with age for subjects 3 to 20 years for each of the first four demands (3 D, 3.92 D, 4.80 D, 5.67 D, p <or= 0.013) and approached significance for the largest demand (6.52 D, p = 0.053). For the entire group, accommodative lag increased with increasing stimulus demand, with the largest increase occurring for subjects aged 30 to 40 years as stimulus demands approached the subjects' maximum amplitude. For subjects aged 3 to 20 years, multilevel modeling analysis revealed a significant relationship between age and lag (p < 0.0001) and a significant relationship between maximum amplitude and the increase in lag per unit increase in stimulus demand (p = 0.0032).

Conclusions: These findings suggest the accuracy of accommodation to minus lens-stimulated accommodation improves throughout the school years and that the degree to which lag increases with increasing demand is related to maximum accommodative amplitude rather than age.

Figure 1

Mean accommodative lags for each 5 year age-bin (3-5 yrs n = 22, 6-10 yrs n = 12, 11-15 yrs n = 13, 16-20 yrs n = 10, 21-25 yrs n = 10, 26-30 yrs n = 15, 31-35 yrs n = 10, 36-40 yrs n = 10). Error bars show ±1 SD of average group responses. In general, lags increased with an increasing stimulus demand. Lags decreased with increasing age from 3 to 20 years.

Figure 2

Individual subjects' data (aged 3 to 20 yrs) for each stimulus demand tested (A-E). Error bars show ±1 SD for each subject for three repeated measurements. Accommodative lag showed a significant linear decrease with increasing age for the first four demands tested (p < 0.02) and approaches significance at the largest demand (p = 0.053).

Figure 2

Individual subjects' data (aged 3 to 20 yrs) for each stimulus demand tested (A-E). Error bars show ±1 SD for each subject for three repeated measurements. Accommodative lag showed a significant linear decrease with increasing age for the first four demands tested (p < 0.02) and approaches significance at the largest demand (p = 0.053).

Figure 2

Individual subjects' data (aged 3 to 20 yrs) for each stimulus demand tested (A-E). Error bars show ±1 SD for each subject for three repeated measurements. Accommodative lag showed a significant linear decrease with increasing age for the first four demands tested (p < 0.02) and approaches significance at the largest demand (p = 0.053).

Figure 2

Individual subjects' data (aged 3 to 20 yrs) for each stimulus demand tested (A-E). Error bars show ±1 SD for each subject for three repeated measurements. Accommodative lag showed a significant linear decrease with increasing age for the first four demands tested (p < 0.02) and approaches significance at the largest demand (p = 0.053).

Figure 2

Individual subjects' data (aged 3 to 20 yrs) for each stimulus demand tested (A-E). Error bars show ±1 SD for each subject for three repeated measurements. Accommodative lag showed a significant linear decrease with increasing age for the first four demands tested (p < 0.02) and approaches significance at the largest demand (p = 0.053).

Figure 3

An example of a single 15 year old subject's stimulus-lag function and a single 6 year old subject's stimulus-lag function used in the multi-level modeling analysis of factors predicting differences in lag among subjects aged 3 to 20 years.

Figure 4

Stimulus response functions for children (A) and adults (B) obtained by lens blur versus proximal blur. The AEI is the calculated accommodative error index and represents the area between the 1:1 line and the stimulus response curve divided by the coefficient of determination.

Figure 4

Stimulus response functions for children (A) and adults (B) obtained by lens blur versus proximal blur. The AEI is the calculated accommodative error index and represents the area between the 1:1 line and the stimulus response curve divided by the coefficient of determination.

Figure 5

Accommodative lag measured when subjects were given specific instructions on which part of the target to view. Group means ±1 SD are shown for 9 children aged 3 to 7 years and 9 adults aged 23 to 29 years.