Abstract
Purpose: :
To describe and compare changes in refractive error and ocular components before and after the onset of myopia among Singapore children.
Methods: :
Annual data collected from 877 children aged 6 to 10 years at initial visit and with at least three visits were analyzed. Cycloplegic refractive error and biometry measures were measured using an autorefractor and A-scan ultrasound machine. Growth and rate-of-change curves of children who began with emmetropia (spherical equivalent, SE being between -0.50D and -1.00D) on at least the first visit and demonstrated at least -0.50D at one or more subsequent visits were constructed and compared with respect to age, gender and ethnicity-matched values derived from the emmetropia models.
Results: :
Children with newly developed myopia became more myopic from 3 years before onset (Mean SE=0.42D) as compared to matched-emmetropia (Mean SE=0.70D) over the same period. A mean SE of -0.5D was observed at approximately 6 months prior to the year of their myopia onset. Their rate of change followed a U-shaped pattern with a trough at approximately 1 year after onset, while the rate for matched-emmetropia remained constant. When compared to matched-emmetropia, more rapid elongation of AL and VCD from 3 years before onset was observed for children who had newly developed myopia. The growth for ACD before and after the onset showed an inverted U-shape curve for both groups. The ACD for children with newly developed myopia deepened more rapidly than those with matched-emmetropia, between 3 years before and 2 years after the onset of myopia. When the rates of change in LT and CR were compared, no clear differences were identified between groups.
Conclusions: :
Our cohort study found that Chinese children eyes had more negative refractive error, grew longer axially, and had increasing vitreous and anterior chambers depth in the 2 to 3 years prior to myopia onset. The differences in corneal radius of curvature and thickness of lens were minimal between children with newly developed myopia and those with emmetropia. Refractive errors and ocular components including AL, VCD and ACD could be useful in predicting the final refractive status of children.
Keywords: myopia • refractive error development