Findings from a recent study published in The Open Ophthalmology Journal found that obesity more than doubled the odds of astigmatism in school-aged children and adolescents.
The risk climbed steadily across nutritional categories, while myopia showed no such link.
Give me some background first.
Some context: Obesity is now the most common form of malnutrition worldwide, with over 160 million children and adolescents affected as of 2022, per Lancet data.
Astigmatism is the most common refractive error in kids, and uncorrected cylinder of ≥1.00 D (diopters) can drag down visual development and academic performance.
- Yet most work tying nutrition to refractive error has centered on myopia, leaving the obesity-astigmatism question in children mostly unexamined.
And what’s the proposed mechanism?
The study’s investigators reasoned that, mechanistically, Grosvenor's eyelid pressure theory states that tension from the lids shapes corneal astigmatism.
“This process may potentially be amplified by obesity-induced orbital changes,” they added.
Plus: Earlier research flagged high body mass index (BMI) as an independent risk factor for astigmatism in adults.
Now, talk about the study.
A team at the Second Affiliated Hospital of Nantong University ran a cross-sectional study in 2023 using the Nantong School-aged Children Eye Study (NSES) database, pulling from 30 primary and secondary schools across Nantong, China.
- The question: Does nutritional status independently raise astigmatism risk in children and adolescents?
Investigators paired anthropometric and refractive data, then ran univariate and multivariate logistic regression to find out.
Who was included in the study?
A total of 9,458 students made the final analysis. 53.2% were male, mean age was 13.3 years, ranging from 7 to 20.
Astigmatism was defined as cylinder ≥1.00 D on subjective refraction. Nutritional status was sorted by Chinese pediatric screening standards into obesity, overweight, normal, and malnutrition.
Exclusions included: systemic disease affecting BMI, ocular pathology, prior eye surgery, and any history of orthokeratology or contact lens wear.
Across the whole cohort, astigmatism prevalence was 28.5%, obesity 11.8%, overweight 11.4%, and malnutrition 11.4%.
Findings?
Astigmatism became more common as body weight increased, rising from 21.1% in children with malnutrition to 25.7% in those of normal weight, 35.3% in those who were overweight, and 40.7% in those with obesity.
After adjusting for age, sex, refractive state, and blood pressure:
- Obese participants were 2.01 times more likely to have astigmatism (aOR 2.01, 95% CI 1.74 to 2.31, p < 0.001)
- Overweight participants were 1.48 times more likely (aOR 1.48, 95% CI 1.31 to 1.69, p < 0.001)
Of note: Nutritional status showed no significant association with myopia after adjustment (p > 0.05).
Tell me more.
Compared with emmetropes, hyperopes were 2.63 times more likely to have astigmatism and myopes 2.43 times. Older age nudged the odds up modestly (aOR 1.11).
With the rule (WTR) astigmatism was by far the most common form, comprising 85.6% of the cohort and 96.3% of astigmatism cases.
WTR carried 8.6 times the astigmatism prevalence of oblique (OBL) axes, the pattern that would be expected if vertical eyelid pressure were steepening the cornea.
Limitations?
The cross-sectional design ruled out any causal claim. The authors also noted two measurement gaps:
- No corneal topography: so they couldn't isolate corneal astigmatism's contribution to total astigmatism or how it interacts with weight.
- Non-cycloplegic refraction: which likely overestimated myopia prevalence, though prior work found the effect on astigmatic measurements is minimal.
Expert opinion?
The authors' position: obesity-related periorbital fat raises eyelid tension and alters corneal curvature, and the heavy WTR predominance in this cohort fits that mechanical model.
Take home.
In this cohort of nearly 9,500 children, the odds of clinically meaningful astigmatism rose steadily with increasing weight, reaching approximately twice as high among children with obesity.
In practice: Weight is worth treating as a risk marker when screening pediatric patients, particularly for the WTR type that this population skews toward.