Do boys and girls differ in how their eyesight develops during childhood, and does any gap widen as they get older? Researchers set out to answer this using school vision-screening records.
They analysed 4.47 million valid screening records from 1,623,070 students aged 3 to 18 in Southern Fujian, China, collected between 2021 and 2024. Eyes were measured with an automatic machine, without eye drops to relax the eye's focusing (non-cycloplegic autorefraction).
Equal at preschool, then girls pulled behind
The main measure was "spherical equivalent" (SE), a number in dioptres (D) that describes the eye's focusing power. The more negative the number, the more short-sighted (myopic) the eye.
- Preschool (6 and under): little difference, +0.04 D, very slightly favouring girls.
- Primary school (7-12): girls were 0.12 D more short-sighted than boys.
- Junior high (13-15): the gap peaked at 0.20 D.
- Senior high (16 and over): the gap eased slightly to 0.17 D, in two of the three cities studied.
Across all ages, being female was linked to a lower SE of 0.141 D. It was also linked to higher odds of myopia (odds ratio 1.18) and of visual impairment (odds ratio 1.26). An odds ratio above 1 means the outcome was more likely in girls. The gap changing with age was statistically significant.
By 16 and over, 88.7% of girls were short-sighted, against 80.4% of boys
Even where the SE gap narrowed, myopia was still more common in girls. Among students aged 16 and above, 88.7% of girls had myopia, against 80.4% of boys, a difference of 8.3 percentage points. Myopia was very common in both sexes by this age.
The catch: a snapshot, not a follow-up of the same children
This was a cross-sectional study, meaning it compared different groups of children at different ages rather than following the same children over time. It cannot show that girls' eyes worsen faster as they grow, or explain why. The authors suggest the patterns may reflect development or differences in earlier generations' exposures, but they did not test this.
The analysis adjusted only for age and city, so factors such as screen time, time outdoors, or family history were not accounted for. The eye measurements were also taken without relaxing drops. The study covers one region of China and did not look at Singapore, so we cannot say the same pattern holds here.
Checking girls' eyes early: what the Fujian numbers suggest
The authors call for earlier and more intensive screening for girls. For parents, the findings support three modest steps:
- The gap first appeared at ages 7-12, so make sure daughters have their vision checked in primary school.
- The gap peaked at ages 13-15, so keep up eye checks through the junior high years rather than stopping after primary school.
- Myopia affected 80.4% of boys aged 16 and above too, so do not assume sons can skip vision checks.