Change in vision disorders among Hong Kong preschoolers in 10 years

Background: To determine the change in refractive error and the prevalence of amblyopia and strabismus among preschool children in Hong Kong over a period of 10 years. Design: Two cross-sectional population-based studies conducted in 1996 to 1997 (part A) and 2006 to 2007 (part B) Participants: Children attending randomly selected kindergarten participated in the study. Methods: Ocular alignment, visual acuity, cover and uncover tests, cycloplegic refraction, slit-lamp and fundi examination were performed under a standardized testing environment. Main Outcome Measures: The prevalence of amblyopia (best-corrected visual acuity <= 6/12 in one or both eyes, or a bilateral difference of >= 2 best-corrected visual acuity lines), strabismus and significant refractive error (hyperopia >=+2.50 D; myopia >=-1.00 D; astigmatism >= 2.00 D) among preschool children. Results: Of the 601 children in part A of the study, reduced visual acuity was presented in 3.8%; whereas strabismus was found in 1.8%. The commonest type of refractive error was astigmatism in 6.3% of children, followed by hyperopia (5.8%) and myopia (2.3%). Among 823 children in part B, reduced visual acuity was presented in 2.7% of children, and strabismus was found in 1.7%. The commonest type of refractive error was myopia (6.3%), followed by astigmatism (5.7%) and hyperopia (5.1%). The percentage of children having myopia has significantly increased (P = 0.001). Conclusion: A significant increase in myopia has been noted in Hong Kong preschoolers. Visual screening programmes may need to be tailored to correspond to the local population and be adjusted accordingly from time to time.