To evaluate changes in refractive errors and quantify optometric values in 4th graders at an urban elementary school in Korea.

A total of 188 school children (376 eyes) were assessed in a population-based, cross-sectional and longitudinal follow-up study between March and December 2003. Uncorrected visual acuity, best corrected visual acuity, corneal refractive power measured with auto keratometer (KR-8100, Topcon^® Inc., Japan), axial length measured with A-scan ultrasound biometry (A/B-scan system 835, Humphrey^® Inc., Dublin, CA), and cycloplegic refraction were evaluated on March and December, respectively.

Mean visual acuity decreased from -0.15±0.29 LogMAR to -0.20±0.35 LogMAR and mean spherical equivalent (SE) showed myopic progression from -0.65±1.57 diopter (D) to -0.88±1.75D. The prevalence rate of myopia (≤-0.50D SE) was increased from 44.1% to 50.3%, while that of hyperopia (≥+1.00D SE) was decreased from 8.0% to 5.8%. Mean corneal refractive power changed from 43.21±1.29D to 43.35±1.31D, and mean axial length changed from 23.38±0.88 mm to 23.60±0.92 mm, respectively.

We assessed the changes of refractive errors and quantified the optometric values in a population-based, longitudinal follow-up study. The results showed that the prevalence of myopia and the mean axial length increased during our study in urban elementary 4th graders in Korea.