Passive smoking exposure might be associated with hypermetropia

The aim of the study was to explore the relationship between nicotine exposure in children via passive smoking and the refractive errors of these children.

The study included 300 children between the age of 5 and 12 years. Children were subjected to detailed history taking with special emphasis on the degree of exposure to passive smoke. They underwent a complete ophthalmological evaluation including cycloplegic refraction. Urine samples were collected to measure urinary levels of cotinine and creatinine with subsequent calculation of the cotinine creatinine ratio (CCR).

The refractive error assessment indicated 122 hypermetropic (40.7%), 86 myopic (28.7%) and 92 emmetropic (30.7%) children. Gender and age were not statistically different between the three groups. Urinary cotinine was significantly higher in the hypermetropic than myopic and emmetropic groups (p < 0.0001). Moreover, it was significantly higher in the emmetropic group than the myopic one (p = 0.02). Cotinine/creatinine ratio (CCR) and the parental number of cigarettes smoked per day showed the same pattern as urinary cotinine. Considering all 300 data, the spherical equivalent refractive error was significantly correlated with the number of cigarettes smoked by the parents, CCR and urinary cotinine levels cotinine (p < 0.0001 for all correlations).

Passive smoking indices were related to the degree of refractive error and children with hypermetropia showed significantly higher passive smoking indices. We suggest that passive smoking might be associated with a refractive error shift towards hypermetropia.