IQ and the association with myopia in children.
OBJECTIVE
To evaluate the association between intelligence and myopia in children.


METHODS
Cycloplegic refraction and ocular biometry parameters, including axial length, vitreous chamber depth, lens thickness, anterior chamber depth, and corneal curvature were obtained in 1204 Chinese school children aged 10 to 12 years from three schools who were participants in the Singapore Cohort Study Of the Risk Factors for Myopia (SCORM). Intelligence quotient (IQ) was assessed using the nonverbal Raven Standard Progressive Matrix test.


RESULTS
After controlling for age, gender, school, parental myopia, father's education, and books read per week, myopia (spherical equivalent [SE]) of at least -0.5 D was associated with high nonverbal IQ (highest quartile) versus low IQ (lowest quartile) (odds ratio = 2.4; 95% confidence interval, 1.7-3.4). Controlling for the same factors, children with higher nonverbal IQ scores had significantly more myopic refractions (-1.86 D for children with nonverbal IQ in the highest quartile compared with -1.24 D for children with nonverbal IQ in the lowest quartile; P = 0.002) and longer axial lengths (24.06 mm versus 23.80 mm; P = 0.022). Nonverbal IQ accounted for a greater proportion of the variance in refraction compared with books read per week.


CONCLUSIONS
Nonverbal IQ may be an independent risk factor of myopia, and this relationship may not be explained merely by increased reading (books per week) among myopes. An interesting observation is that nonverbal IQ may be a stronger risk factor for myopia compared with books read per week. The complexity of the relationships between nonverbal IQ, reading, and myopia warrant additional studies to clarify any cause-effect relationship.
Saw
Seang-Mei
SM
Department of Community, Occupational and Family Medicine, National University of Singapore. cofsawsm@nus.edu.sg
Tan
Say-Beng
SB
Fung
Daniel
D
Chia
Kee-Seng
KS
Koh
David
D
Tan
Donald T H
DT
Stone
Richard A
RA
D001877:Books; D002675:Child, Preschool; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008962:Models, Theoretical; D015999:Multivariate Analysis; D009216:Myopia / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology / Q000523:psychology*; D015995:Prevalence; D011932:Reading; D012029:Refraction, Ocular; D012307:Risk Factors