Progression of school myopia from its onset at the mean age of 10.9 years:: 13-year follow-up study

Myopic progression among 240 school children was followed up from its onset at the mean age of 10.9 years in a clinical trial of myopia treatment. The children were randomly allocated to three different groups according to the recommended use of spectacles: continuous use, only for distant use, and bifocals with a 1.75 D add. Altogether 238 of them were followed annually for 3 years. A further control examination was conducted for 179 (74.6%) of them 10 years after the end of the treatment trial. For 150 subjects additional refraction values were obtained from the earlier prescriptions. The mean initial spherical equivalent of the right eye at the beginning of the study was -1.46 D (range -0.35 to -3.0) and increased during the 3-year follow-up to -3.13 D. Ten years later the mean myopia had increased to -4.69 D (range +0.25 to -10.75). The increase in myopia could be explained by the increase in vitreous length. There was a negative correlation between axial length and corneal refractive power. The females had higher myopia with higher corneal power and shorter axial length than the males. Although mean refraction showed a slight continuous increase up to adult age, considerable individual variation in long term myopic progression was found.