Comparison of aberrometer and autorefractor measures of refractive error in children.

PURPOSE: The purpose of this study was to evaluate and compare the Complete Ophthalmic Analysis System (COAS) G200 Aberrometer (Wavefront Sciences Inc., Albuquerque, NM) and Canon RK-F1 Autorefractor (Canon Inc., Tokyo, Japan) for measuring refractive errors in young children. METHODS: The Sydney Myopia Study is a population-based study of refractive error and eye health in young Australian children. Cycloplegic refractions were performed on 1504 school year 1 students (mostly 6 years old) and 890 school year 7 (mostly 12 years old) students using both the COAS G200 Aberrometer and Canon RK-F1 autorefractor. Refractive data were analyzed using power vectors. Mean differences and 95% limits of agreement were determined for refractive components between the two instruments. RESULTS: The mean age +/- standard deviation was 6.7 +/- 0.4 years (range, 5.5-9.1 years) and 12.6 +/- 0.5 years (range, 11.1-14.4 years) for the year 1 and year 7 students, respectively. Mean paired differences for the M component (spherical equivalent) between the COAS G200 and Canon RK-F1 were <0.25 D in both age groups and were statistically significant in the year 1 group only (p < 0.001). Small significant differences were found in the astigmatic components (J0 and J45) in both groups. A smaller coefficient of agreement for the M component was found in the older group (0.54 D), whereas the coefficients of agreement of the astigmatic components (J0 and J45) were similar for both groups. CONCLUSIONS: The COAS G200 aberrometer was an easy-to-use instrument for the measurement of refractive error in children. In addition to being able to measure higher and lower order aberrations, the COAS G200 provides refractive error measurements comparable to those of an autorefractor.

Accommodative facility in eyes with and without myopia.

PURPOSE: To compare accommodative facility in eyes with myopia to that in eyes with emmetropia or hyperopia and to determine whether accommodative facility can be used to predict an association with myopia. METHODS: In the Sydney Myopia Study, year-1 school children (6.7 +/- 0.4 years) were assessed for accommodative facility at distance (3 m) and near (33 cm) with semiautomated flippers. Spherical equivalent refractive error (RE) was defined as myopia (< or = -0.50 D), emmetropia (> -0.50 D, but < +1.50 D), and hyperopia (> or = +1.50 D) based on postcycloplegia readings. Only right eye data were considered. Differences between groups were analyzed with the Brown-Forsythe F test after adjustment for age and gender. Multiple comparisons were adjusted with the by the Games-Howell RESULTS: Of the 1328 right eyes assessed, 20 (1.5%) eyes were myopic, 977 (73.6%) were emmetropic, and 331 (24.9%) were hyperopic. At distance, mean facility was less for myopic eyes at 5.5 +/- 2.0 cycles per minute (cpm) in comparison to 6.9 +/- 1.7 cpm for eyes with emmetropia or hyperopia (P = 0.005). Myopic eyes recorded greater positive and negative accommodative response times than did emmetropic or hyperopic eyes (P < 0.05). There were no differences among the groups in near facility. The area under the receiver operating characteristic (ROC) curve for distance facility was 0.692 (P = 0.003, 95% CI, 0.580-0.805). CONCLUSIONS: Myopic eyes have reduced accommodative facility at distance, and accommodative responsiveness to both positive and negative defocus is slow. However, accommodative facility as a test does not have sufficient power to discriminate eyes with myopia from other refractive errors.