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(HealthDay)—Exposure to secondhand smoking is associated with choroidal thinning among children aged 6 to 8 years, according to a study published online Oct. 17 in JAMA Ophthalmology.

Nan Yuan, from The Chinese University of Hong Kong, and colleagues recruited children aged 6 to 8 years from the population-based Hong Kong Children Eye Study to examine the correlation between choroidal thickness and exposure to secondhand smoke. Data were included for 1,400 children.

The researchers found that 67.2 percent of the children had no exposure to secondhand smoking, while 32.8 percent had exposure. Exposure to secondhand smoking correlated with a thinner choroid by 8.3, 7.2, 6.4, 6.4, and 7.3 µm in the central subfield, inner inferior, outer inferior, inner temporal, and outer temporal, respectively, after adjustment for age, sex, body mass index, axial length, and birth weight. There was also a correlation for choroidal thinning with increased number of family smokers and increased quantity of secondhand smoking. Per one family smoker increase, choroidal thinning increased by 7.86, 4.51, 6.23, 5.59, 6.06, and 6.55 µm in the central subfield, outer superior, inner inferior, outer inferior, inner nasal, and outer nasal, respectively. Per one secondhand cigarette smoke exposure increase per day, choroidal thinning increased by 0.54, 0.42, and 0.47 µm in the central subfield, inner temporal, and outer temporal, respectively.

"These findings add to the potential harmful effect of secondhand smoking on children's ocular health and development," the authors write. One author disclosed financial ties to the pharmaceutical industry.