|Title||LOG-SPLINE ESTIMATION OF THE DISTRIBUTIONS OF REFRACTIVE ERROR AND THE OCULAR COMPONENTS|
|Author, Co-Author||Karla Zadnik, Donald Mutti, Robert Sholtz, Nina Friedman, Robert Fusaro|
Northern Hem E4
|Abstract|| PURPOSE: The question of how the distributions of the individual ocular optical components result in the leptokurtic, skewed (towards myopia) distribution of refractive error can be found throughout the classical myopia literature. We wanted to characterize the distributions of the ocular components by age using a flexible, non-parametric method.
METHODS: Using log-spline methods free from parametric assumptions about the underlying distribution, we fit density estimates to data collected in fall 1993 from the Orinda Longitudinal Study of Myopia. Children were placed into four groups by age: 6-7 (n = 242), 8-9 (n = 192), 10-11 (n = 156), and >=12 years old (n = 180).
RESULTS: Increase in myopic skew is apparent in the distributions of both refractive error (REF) and vitreous chamber depth (VCD) when the youngest and oldest age groups are compared (skew REF +/-2 SEs = -0.76 +/- 0.66 for ages 6-7, -1.75 +/- 1.05 at age >=12; skew VCD +/-2 SEs = 0.14 +/- 0.66 at age 6-7, 0.60 +/- 0.81 at age >=12). Vitreous chamber depth shows a sustained increase in mean values throughout childhood, but median VCD shows little change in later childhood (median = 16.0 mm at ages 10-11; 16.1 mm at >=12 years). Distributions of anterior chamber depth, lens thickness, Gullstrand lens power, and calculated lens power show little departure from normality at any age. Changes with age for these components are consistent with our previous reports using these data.
CONCLUSIONS: Ocular component distributions are essentially normal except for refractive error and vitreous chamber depth. Myopic skew in the distribution of refractive error, representing an increase in the prevalence of myopia in later childhood, may be due to an increase in the skew toward longer eyes in the distribution of vitreous chamber depth, rather than to an overall increase in vitreous chamber depth. Supported by NIH-NEI U10-EY08893.
|Affiliation of Co-Authors||Ohio State University, University of California, University of California, University of California|