Findings from a recent study published in the Canadian Journal of Ophthalmology tracked more than 22,000 children over roughly 5 years and found that those that were overweight or obese had higher odds of developing astigmatism than their normal-weight peers.
The association grew stronger as body weight climbed.
Give me some background first.
Some context: Childhood overweight and obesity have become a global public health concern, with effects that reach past metabolic and cardiovascular health into how the eye develops.
Astigmatism is one of the more common refractive errors in children.
Left uncorrected, it can stall visual development and raise the risk of amblyopia. It has also been tied to weaker performance in school.
And the issue?
Whether body weight itself shapes that astigmatism risk has stayed murky.
Earlier research linking body mass index (BMI) to astigmatism was mostly small or cross-sectional, and the results didn't line up.
- The largest prior effort, a nationwide study of Israeli adolescents, found a dose-dependent link, with severe obesity tied to a 1.65-fold higher astigmatism risk in males and 1.74-fold in females.
Now, talk about the study.
The researchers ran a population-based retrospective cohort study using records from Maccabi Healthcare Services, Israel's second-largest health organization, which covers more than a quarter of the country.
The question: does childhood obesity precede the development of astigmatism, rather than just showing up alongside it?
Who was included in the study?
Investigators analyzed 22,130 children aged 6 to 10 at baseline who had a refractive assessment between 2012 and 2022 and at least 2 years of follow-up. They started with 23,051 kids and excluded 921 (4.0%) for concurrent eye pathology, high astigmatism at baseline, or missing BMI data.
Demographics: 53.6% were female. Mean follow-up ran 62.9 months, about 5.2 years, and mean age at follow-up was 13.6 years. Right eye data were used for analysis, given the strong correlation between eyes.
BMI was sorted using age- and sex-specific percentiles from the U.S. Centers for Disease Control and Prevention into underweight, normal, overweight, and obesity. Astigmatism (≥0.75 D) was split into low-to-moderate (0.75 to <3.00 D) and high (≥3.00 D).
Findings?
Astigmatism at follow-up rose steadily with baseline BMI (p < 0.001). Low-to-moderate astigmatism went from 29.8% in normal-weight children to 32.1% in overweight and 35.1% in those with obesity. High astigmatism followed the same track, climbing from 1.1% to 1.6% to 2.0%.
After adjusting for age, sex, baseline astigmatism, socioeconomic status, and country of birth, the odds ratios (ORs) held up. Compared with normal weight, overweight carried a 10% higher odds of low-to-moderate astigmatism (OR 1.10) and a 40% higher odds of high astigmatism (OR 1.40). Obesity pushed those to 24% (OR 1.24) and 76% (OR 1.76).
Tell me more.
Dose matters: each 1-unit rise in BMI was tied to 2.4% higher odds of low-to-moderate astigmatism (OR 1.024) and 8.2% higher odds of high astigmatism (OR 1.082).
The excess risk clustered in one axis type. Higher BMI was linked to against-the-rule (ATR) astigmatism, strongest in obesity (OR 1.41), while with-the-rule and oblique astigmatism showed no significant association. ATR astigmatism at follow-up rose from 20.1% in normal-weight children to 27.2% in those with obesity.
Worth noting: overweight and obesity together accounted for 4.3% of low-to-moderate and 13.4% of high astigmatism cases in this cohort.
Limitations?
BMI doesn't separate fat from lean mass or capture where fat sits, which may matter for the eye. Key confounders were adjusted for, but others like genetics, environment, and eye rubbing weren't measured.
Refraction was performed by multiple ophthalmologists, introducing interexaminer variability, and the database couldn't confirm whether the same examiner handled both baseline and follow-up. Follow-up also wasn't standardized. Some children returned based on clinical need rather than a fixed schedule, which could skew the sample toward symptomatic kids.
Expert opinion?
No outside commentary was included in the study.
Their position: the authors argued the findings underscore how far childhood obesity's effects reach, and they called for a multidisciplinary approach linking pediatric and ophthalmologic care. If confirmed, they wrote, BMI could serve as one factor informing vision screening and follow-up.
Anything else?
The authors floated both systemic and local mechanisms. On the systemic side, obesity-related shifts in leptin, insulin resistance, and oxidative stress may affect corneal biomechanics. Locally, added periocular fat and eyelid pressure could alter corneal curvature.
The open question: which of these dominates, and how age, ethnicity, and eyelid anatomy change the picture. The ATR skew here runs counter to some earlier work that reported a shift toward with-the-rule astigmatism at higher BMI, a gap the authors tied to differences in age and study population. They called for future studies pairing metabolic and biomechanical measures across more diverse groups.
Take home.
Children carrying extra weight showed higher, dose-dependent odds of astigmatism about five years down the line. For clinicians, an elevated BMI may be a practical flag for closer refractive monitoring, so astigmatism gets caught and corrected before it interferes with a child's visual development.