Risk Factors for Refractive Errors in Preschool Children
We studied parental history, near work, and intraocular pressure as risk factors for eye size and refractive error in preschool children. This age group (3-6 years) was selected on the assumption that genetic influences on eye growth would outweigh environmental factors at this stage. A total of 527 children underwent cycloplegic refraction, keratometry, tonometry, and ultrasound biometry. They were asked to complete a near-work diary (MIRF Visual Exposure Index). The axial lengths of the children were found to be not correlated with parental myopia: No parents were myopic 21.72 mm; one parent was myopic 21.85 mm; both parents were myopic 21.75 mm. Near work was analyzed as the product of the working distance and time spent in various forms of near tasks. Although near work increased from 1.0 to 1.5 h with age from 3 to 5 years, there was no significant correlation of near work with either refractive error or axial length. The parental history of myopia and the amount of near work were thus not predictors of eye size in preschool children. A high prevalence of against-the-rule astigmatism was found, which did not decline with age from 3 to 5 years. Intraocular pressure (IOP) increased with age. Moreover, increasing IOP was correlated with increasing myopia. Similarly, the parental history of myopia was predictive of higher IOP in the child: no myopic parents 13.54 mmHg, one myopic parent 14.11 mmHg, two myopic parents 14.43 mmHg.