The Centers for Disease Control and Prevention estimates that 34.3 million adults in the United States currently smoke cigarettes and that more than 16 million live with a smoking-related disease, many of which affect the cardiovascular system. Cigarette nicotine deprivation in chronic users may impair cognitive and attentional abilities even after long time of cessation. The neurotoxic effects of chronic use and smoking abstinence on the nervous system have not been extensively studied. However, chronic cigarette smoking increases cardiovascular response, which, in turn, affects retinal responses through altered blood flow. In addition, tobacco compounds may increase free radical that would cause macular degeneration along with the action of ischemia. Whereas smoking effects on color vision are understudied, the existing data are controversial and highlights the importance of a rigorous testing procedure that measures color discrimination. Previous studies have pointed to long-term smoking as doubling the risk for age-related macular degeneration and as a factor causing lens yellowing and inflammation. Now, Rutgers researchers found that smoking more than 20 cigarettes a day can damage vision.
The study included 71 healthy people who smoked fewer than 15 cigarettes in their lives and 63 who smoked more than 20 cigarettes a day, were diagnosed with tobacco addiction and reported no attempts to stop smoking. The participants were between the ages of 25 and 45 and had normal or corrected-to-normal vision as measured by standard visual acuity charts. The researchers looked at how participants discriminated contrast levels (subtle differences in shading) and colors while seated 59 inches from a 19-inch cathode-ray tube monitor that displayed stimuli while researchers monitored both eyes simultaneously. The findings indicated significant changes in the smokers’ red-green and blue-yellow color vision, which suggests that consuming substances with neurotoxic chemicals, such as those in cigarettes, may cause overall color vision loss. They also found that the heavy smokers had a reduced ability to discriminate contrasts and colors when compared to the non-smokers. Although the research did not give a physiological explanation for the results, since nicotine and smoking harm the vascular system, the study suggests they also damage blood vessels and neurons in the retina.
Cigarette smoke consists of numerous compounds that are harmful to health, and it has been linked to a reduction in the thickness of layers in the brain, and to brain lesions, involving areas such as the frontal lobe, which plays a role in voluntary movement and control of thinking, and a decrease in activity in the area of the brain that processes vision. Carbon monoxide, hydrogen cyanide and formaldehyde are the most enriched toxic gaseous components that may directly harm human retinal cells. In addition, tobacco compounds may increase free radical generation (oxidative stress) that would cause macular degeneration along with the action of ischemia on local blood vessels. Dr Steven Silverstein, director of research at Rutgers University Behavioral Health Care, said: ” Our results indicate that excessive use of cigarettes, or chronic exposure to their compounds, affects visual discrimination, supporting the existence of overall deficits in visual processing with tobacco addiction. Overall, data also suggest that research into visual processing impairments in other groups of people, such as those with schizophrenia who often smoke heavily, should take into account their smoking rate or independently examine smokers versus non-smokers”.
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Fernandes TP et al. Psychiatry Res. 2019 Jan; 271:60-67.
Nita M, Grzybowski A.Curr Pharm Des. 2017; 23(4):639-54.
George AK et al. Int J Ophthalmol. 2018 May 18;11(5):881.
Datta S et al. Prog Retin Eye Res. 2017 Sep; 60:201-218.