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Iris colour and astigmatism among Chinese teenagers
  1. Chen-Wei Pan1,
  2. Chaofu Ke1,
  3. Dan-Ning Hu2,
  4. Jun Li3,
  5. Hua Zhong4
  1. 1School of Public Health, Medical College of Soochow University, Suzhou, China
  2. 2New York Eye and Ear Infirmary at Mount Sinai, Icahn School of Medicine at Mount Sinai, New York City, New York, USA
  3. 3Department of Ophthalmology, The Second People’s Hospital of Yunnan Province, Kunming, China
  4. 4Department of Ophthalmology, The First Affiliated Hospital of Kunming Medical University, Kunming, China
  1. Correspondence to Professor Hua Zhong, Department of Ophthalmology, The First Affiliated Hospital of Kunming Medical University, Kunming 650032, China; zhoculist{at}


Background/aims Iris colour might contribute to refractive development, but it is uncertain whether it is related to astigmatism. We aim to examine the association of iris colour with the presence of astigmatism in a school-based sample of Chinese students.

Methods 2346 grade 7 students from 10 middle schools aged 13 to 14 years in Southwestern China participated in the study. We obtained standardised slit-lamp photographs and developed a grading system assessing iris colour (higher grade denoting darker). Astigmatism was defined as a cylinder power of more than 0.50, 0.75 or 1.00 dioptre (D). Logistic regression models with generalised estimating equation were fitted to assess the relationship between iris colour and astigmatism, accounting for the correlation between both eyes. ORs and 95% CIs were presented.

Results The overall prevalence of astigmatism for three different definitions was 30.4% (95% CI 28.6% to 32.2%) (<−0.5 D), 12.7 % (95% CI 11.3% to 14.0%) (<−0.75 D) and 5.3% (95% CI 4.4% to 6.2%) (<−1.0 D), respectively. In multivariate analysis adjusting for the effect of gender and height, darker iris colour was associated with an increasing trend of astigmatism (p for trend <0.05). Compared with individuals with iris colour of grade 4 or 5 (the darkest), those with grade 1 or 2 (the lightest) were significantly less likely to be affected by astigmatism (<−0.75 D) in gender-adjusted model (OR 0.67) and multivariate-adjusted model (OR 0.72).

Conclusion Darker iris colour might be a risk factor for astigmatism in Chinese adolescents.

  • iris colour
  • astigmatism
  • refractive error
  • epidemiology

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  • C-WP and CK contributed equally.

  • Contributors C-WP and HZ contributed to the formulation of research questions and study design. C-WP and CK conducted statistical analysis and wrote the first draft. All authors contributed to the interpretation of results and the final manuscript.

  • Funding This study was funded by the National Natural Science Foundation of China under grant no. 81502824, no. 81773449 and no. 81560169.

  • Competing interests None declared.

  • Patient consent for publication Parental/guardian consent obtained.

  • Ethics approval The Mojiang Myopia Progression Study was performed in accordance with the tenets of the Declaration of Helsinki and the study protocol was approved by the Institutional Review Board of Kunming Medical University.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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