Characteristics of the participants in five studies.

aInformation of gender and age is based on data from offspring with corneal astigmatism in STARS family cohort. bAveraged across both eyes; NA, not available; Age is in years. SP2 - Singapore Prospective Study Program; SiMES - Singapore Malay Eye Study; SINDI - Singapore Indian Eye Study; SCORM - Singapore Cohort study of the Risk factors for Myopia; STARS - Singaporean Chinese in the Strabismus, Amblyopia and Refractive Error Study.