Visual acuity in childhood poorly predicts myopic status as adults

Low uncorrected distance visual acuity in childhood poorly predicts myopia status in adulthood, according to a study by London researchers. "Only a quarter of individuals ... who had developed myopia by 45 years of age had reduced acuity at 16 years," the study authors said.

Uncorrected distance visual acuity (DVA) in childhood "is therefore an inaccurate and inappropriate intermediate (proxy) 'phenotype' for genetic epidemiological work on myopia," they said.

Phillippa M. Cumberland, and colleagues at the Institute of Child Health obtained current refraction data from 1,867 people aged 44 to 45 years who were members of a British birth cohort study begun in 1958. The investigators compared that refraction data with refractive measurements of each patient obtained when they were 16 years old.

Myopia was generally considered present if DVA at 16 years of age was 6/12 or worse and not present if DVA was 6/9 or better, the authors said.

At 44 to 45 years, 646 adults had a spherical equivalent of –1 or higher, but only 153 (23.7%) of these myopic adults had a DVA of 6/12 or worse at 16 years. Of these myopic people, half who had developed moderate myopia of 2.99 D to 5.99 D and 31% who had developed severe myopia of 6 D or more had good DVA at 16 years, according to the study.

"Although current myopia research tends to the view that most cases of myopia have onset at school age, these findings serve as a reminder that late-onset myopia makes an important contribution to the overall incidence of myopia in some populations," the authors said.

However, subjects with a DVA of 6/12 or worse at 16 years have a 91% lifetime chance of developing myopia of 0.5 D or more, they noted.

"Our findings support the assessment of visual acuity in children of secondary school age as an effective method of identifying undiagnosed refractive error," the authors said. "We suggest that testing using a threshold approach (set at 6/12 Snellen equivalent) for 'failing' screening and thus indicating referral would be appropriate."

The study is published in the February issue of the British Journal of Ophthalmology.