Refractive Error and Axial Length (REAL) Study: Feasibility of a population study in the United States

Myopia is the most common eye disease and a leading cause of blindness. A contemporary, large, and ethnically and geographically diverse study of ocular biometry and refractive error in children in the United States is needed to help better describe differences between myopic and nonmyopic eyes.

This is an initial cross-sectional report from the Refractive Error and Axial Length Growth Curve Study that includes ocular component data as a function of age, gender, and geographic location. This feasibility report will inform a planned larger longitudinal ocular growth study in children in the United States.

Cross-sectional data on children, ages 3 to 8 years, were collected in three geographic regions: Oakland, California (two preschools and one elementary school), Greater Boston, Massachusetts (one preschool and one elementary school), and Houston, Texas (one preschool). Eye examinations took place at preschools and elementary schools in each region. Objective cycloplegic refractive error, ocular biometry, as well as race, height, weight, and waist circumference data were acquired.

Data were collected between May 2023 and May 2024 on a total of 157 children, ages 5.14 ± 1.77 years, with 83 females, 71 males, and two not reported. Right eye mean cycloplegic spherical equivalent refractive error was +0.81 ± 1.46 D (range: -5.88 to +5.75 D), and the mean axial length was 22.47 ± 0.91 mm (range: 20.62 to 25.82 mm). The mean spherical equivalent refractive error did not vary significantly with age. Older children exhibited longer axial lengths, as well as greater height, weight, and waist circumference (p < 0.05 for all).

This feasibility report provides a basis for sample size calculation in preparation for a larger, longitudinal, population-based study. Pilot data show longer axial lengths than previously published data for the same age range, which may indicate generational changes, differences in instrumentation, or differences in race distribution. Updated normative data on eye size and refraction will help eye care professionals diagnose and manage myopia and provide important comparative data for historical and contemporary norms in the United States.