The relationship between serum trace element changes and visual function in heavy smokers

Purpose: The aim of this prospective study was to evaluate serum manganese (Mn), zinc (Zn) and copper (Cu) levels and visual functions including visual acuity, colour vision, pattern visual evoked potentials (PVEPs), and contrast sensitivity in heavy smokers and to compare these with the equivalent levels and functions in non-smokers. Methods: Data were recorded in 24 healthy, chronic and heavy cigarette smokers and 16 healthy, non-smoking control subjects. Serum Zn, Cu and Mn concentrations in all subjects were measured by atomic absorption spectrophotometry. Results: Both study and control subjects had normal visual acuity and colour vision. Pattern visual evoked potentials were normal in all study and control subjects. Contrast sensitivity was significantly reduced in heavy smokers compared to non-smokers (p<0.023), despite the fact that central vision and PVEP responses were not affected. Mean serum Mn and Zn levels were significantly lower in smokers than in non-smokers (p<0.0001 and p<0.005, respectively). Conclusions: Reduced contrast sensitivity values associated with low levels of serum Mn and Zn, which function as cofactors of superoxide dismutase in erythrocyte and other nucleated cells, suggest a possible role of trace elements in smoking-induced early retinal toxicity.