Inclusion criteria
astigmatism, diopter
ASTIGMATISM, MYOPIA
Inclusion criterion for children aged six to nine years was spherical power of ≤ − 1 diopter (D) in at least one eye. Inclusion criterion for children aged nine to twelve years was spherical power of ≤−2 D in at least one eye. The higher ≤ − 2 D criterion for nine- to twelve-year-old children was chosen to ensure myopia progression for all participants, since we had no way of retrieving certain data about prior progression rates. For both age groups, maximum allowed astigmatism at inclusion was less than − 1.5 D.