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
- refractive error
Statistics from Altmetric.com
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.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.