Early contrast sensitivity loss and oxidative damage in healthy heavy smokers

Abstract

Objective: The purpose of this study was 1) to evaluate visual functions and the activities of antioxidant enzymes in plasma and erythrocytes in smokers in comparison with non-smokers, 2) to evaluate the correlations between visual functions and the oxidant/antioxidant system. We hypothesized that the changes in antioxidant system and consequently lipid peroxidation depend on smoking may affect sophisticated visual tests including contrast sensitivity (CS) and pattern visual evoked potentials (PVEP) Subjects: This non-randomised control study included 24 chronic, heavy smokers who were smoking more than 20 cigarettes per day at least for last 10 years. Sixteen age and sex-matched, healthy, non-smokers were taken as controls. All volunteer subjects were accumulated from the outpatient clinic. To rule out the effect of alcoholism and malnutrition, we chose young, healthy heavy smokers who maintained adequate diet and who had no alcohol consumption history. Following visual acuity and color vision tests, all subjects were applied to CS and PVEP tests. Values of CS, N75-P100 amplitude and P100 wave latency were compared between the study and control subjects. Superoxide dismutase (SOD) and catalase (CAT) activities in plasma and erythrocytes were determined by spectrophotometer. Plasma malondialdehyde (MDA) level, as an end product of lipid peroxidation, was assessed by spectrofluorometric method. Results: CS was determined to be significantly reduced in smokers compared to non-smokers, although central vision and PVEP responses were not affected. Erythrocyte SOD activity and plasma MDA levels were significantly increased in smokers compared to controls. There were positive correlations between plasma SOD and erythrocyte SOD; CS and erythrocyte SOD; and CS and plasma SOD. Conclusions: The results suggest the possible association between early CS loss and increase in antioxidant enzyme activities thus reflecting an increased oxidative damage due to cumulative effect of chronic smoking. Elevated concentrations of lipid peroxidation products in the plasma of smokers may directly show the increased oxidative damage in these subjects.