Abstract
Abstract: :
Purpose: Previously we reported that myopic and pre–myopic children had larger accommodative lags than emmetropes and that children with 2 myopic parents were more likely to be myopic than children with 0 or 1 myopic parents. We now investigate the association between accommodation in children and parental myopia. Methods: Accommodation in 85 myopic and emmetropic children was measured with the Canon R–1 open field of view autorefractor for: (1) a 0.33 m target with the child wearing the best correction, (2) a 0.33 m target with a –2.0 D lens over the best correction, and (3) a 4.0 m target with a –3.0 D lens over the best correction. Refractions in children were measured by non–cycloplegic distance retinoscopy and in the parents by retinoscopy, lensometry, or their prescription. Accommodation data from myopic children were taken at the age of myopia onset (mean = 10.5 yrs). Data from emmetropes were taken at the same mean age after insuring that they had remained emmetropic until at least 15 yrs of age. Accommodation in children was analyzed by number of myopic parents (1 vs. 2; too few children had 0 myopic parents). Means and SDs were calculated, and the data were analyzed by ANOVA. Results: Overall, myopes with 2 myopic parents had the largest accommodative lags. Myopes with 1 myopic parent and emmetropes with either 1 or 2 myopic parents had lags of similar and smaller magnitudes. Among children with 2 myopic parents, myopes had significantly larger lags than emmetropes (p < 0.05) for each accommodative condition (increases in lags of 0.33 D, 0.84 D, and 0.58 D for the 3 conditions, respectively). For children with 1 myopic parent, the increases were negligible (–0.03 D, 0.12 D, and –0.03 D). Having 2 vs 1 myopic parent increased lags among myopic children by 0.49 D, 0.77 D, and 0.49 D for the 3 conditions, while the differences for emmetropes were small (0.13 D, 0.05 D, and –0.12 D). Conclusions: Poor accommodation occurs only in newly myopic children with two myopic parents. This result suggests that large accommodative lags, a risk factor for myopia, may have a genetic component.
Keywords: myopia • refraction