Researchers recently found that exposure to secondhand smoke was associated with choroidal thinning that has a dose-dependent effect on children.

From January 2016 to July 2017, the team recruited 941 children who had no exposure to secondhand smoking and 459 who did. The researchers measured choroidal thickness and obtained secondhand smoking history to assess the correlation between the two.

After adjusting for age, sex, body mass index, axial length and birth weight, the investigators discovered that exposure to secondhand smoking was associated with a thinner choroid by 8.3μm in the central subfield, 7.2μm in the inner inferior, 6.4μm in the outer inferior, 6.4μm in the inner temporal and 7.3μm in the outer temporal.

They added that choroidal thinning was associated with increased number of family smokers and increased quantity of secondhand smoke. With each additional family smoker, the study authors noted the choroid thinned by 7.86μm in the central subfield, 4.51μm in the outer superior, 6.23μm in the inner inferior, 5.59μm in the outer inferior, 6.06μm in the inner nasal and 6.55μm in the outer nasal. For each additional cigarette’s worth of secondhand smoke daily, choroidal thinning was impacted by 0.54μm in the central subfield, 0.42μm in the inner temporal and 0.47μm in the outer temporal.

“While it is unknown if there is a causal relationship from this association or if this is due to confounding factors, these findings add to the potential harmful effect of secondhand smoking on children’s ocular health and development,” the researchers concluded in their paper.

Yuan N, Li J, Tang S, et al. Association of secondhand smoking exposure with choroidal thinning in children aged 6 to 8 years. JAMA Ophthalmol. October 17, 2019. [Epub ahead of print].