Urban Chinese children have high prevalence of myopia

Reduced vision because of uncorrected myopia is a major public health problem for school-age children, according to a study in an urban area of China. The study found that school-age children in metropolitan Guangzhou province had a high likelihood of myopia, and one-third did not have the necessary corrective spectacles.

Mingguang He and colleagues from the Zhongshan Ophthalmic Center examined 4,364 children from Guangzhou to determine the prevalence of refractive error and visual impairment. The children underwent complete ophthalmic examinations from October 2002 to January 2003.

The prevalence of uncorrected visual acuity of 20/40 or worse in the better eye was 22%; of presenting VA of 20/40 or worse was 10%, and of best corrected VA 20/40 or worse was 0.6%. In 95% of the 2,335 eyes with reduced vision, refractive error was the cause. Amblyopia accounted for 2% of the instances of refractive error, other causes accounted for 0.4%, and unexplained causes accounted for 3%.

Both external and anterior segment abnormalities, comprising mainly minor conjunctival abnormalities, were seen in 1,496 (34.3%) children. Media and fundus abnormalities were observed in 32 children. Myopia, defined as a spherical equivalent of at least –0.5 D in either eye, affected 73% of the children who were 15 years of age; 78% with autorefraction. Conversely, the presence of myopia in children 5 years old was 3%, and 6% with autorefraction. Females had a slightly higher risk of myopia.

Hyperopia, defined as +2 D or higher, was present in 17% of 5-year-olds, 17% with autorefraction. For 15-year-olds, the prevalence dropped to less than 1% with either measurement factor.

Measured by retinoscopy, 34% of the children had astigmatism (defined as a cylinder of at least 0.75 D). Measured by autorefraction, 43% of the children had astigmatism.

The study is published in the March issue of Investigative Ophthalmology & Visual Science.