Ocular refraction and its components among younger children in Kaohsiung: a 4-year longitudinal study.

A four-year longitudinal study was made on refraction and its components among 50 children of Kaohsiung, Taiwan, R.O.C. aged from 7 to 10.6 years. The methods of examination of the eyes were the same as that of four years ago, including Mydriacyl refraction, keratometry for corneal curvature radius, and ultrasonic measurement of the refractive components. One eye with amblyopia was excluded. The results of our study showed that all of our cases over 6 years of age had a corrected visual acuity of 0.8 or better, and that the refractive state shifted to myopia in our 4-year follow up. The rate of myopia increased from 2% to 27.3%. Comparisons of refractive components between the years 1983 and 1987 showed significant increases in refractive power, length of vitreous cavity and total axial length of the eyes. Corneal refractive power and lens thickness, however decreased significantly. As for differences in gender, several results were the same for both 1983 and 1987: corneal curvature radius, the length from anterior corneal surface to anterior lens surface, length of vitreous cavity and total axial length were larger in males than females. Finally, total axial length and corneal curvature radius were the factors most affecting the refractive state in younger children.