Accommodative lag using dynamic retinoscopy: age norms for school-age children.

BACKGROUND: Nott dynamic retinoscopy (DR) is a technique that provides an objective, rapid assessment of accommodative function. Presently there are no data available regarding age norms of accommodative function for school-age children using Nott DR. METHODS: Accommodative responses were assessed in a group of 125 school-age children (4 to 15 years of age) using Nott DR. A range of accommodative demands was included [4 D (25 cm), 6 D (16.7 cm), and 10 D (10 cm)]. All the subjects had fully corrected refractive errors and a binocular visual acuity of at least 6/6. RESULTS: Accommodative responses were assessed successfully at each distance with all the subjects (N = 125). A mean overall lag of accommodation was noted with each age group at each distance tested. Regression analysis demonstrated no significant difference in accommodative responses between age groups (p = 0.531 at 4 D, p = 0.062 at 6 D, and p = 0.883 at 10 D). Therefore, results for all the age categories were grouped together to produce a table of normal ranges of accommodation for children aged 4 to 15 years for the three stimuli demands. The mean lag of accommodation was found to be 0.30 +/- 0.39 D at 4 D, 0.74 +/- 0.58 D at 6 D, and 2.50 +/- 1.27 D at 10 D. The normal ranges of accommodation (95% confidence limits) were 2.94 to 4.46 D at 4 D, 4.12 to 6.40 D at 6 D, and 5.02 to 10.00 D at 10 D. CONCLUSIONS: A comprehensive table has been produced detailing the mean lags and normal ranges of accommodative responses expected for school-age children when using Nott DR. These data allow practitioners and researchers to determine whether accommodative responses measured using Nott DR are within normal limits.