More than 20 cigarettes a day can significantly damage vision with greater difficulty in distinguishing color contrasts. This was the result of a study by an American research team.
Two groups were compared in the study: 71 participants were healthy volunteers smoking less than 15 cigarettes a day. In parallel, 63 chain smokers with a diagnosed tobacco addiction participated without attempting to quit smoking. All participants were between 25 and 45 years of age and had normal visual acuity or normal visual acuity corrected by a standard visual acuity measurement.
The researchers observed how the study participants distinguished between contrast values and colors. The subjects sat at a distance of about 1.5 meters in front of a monitor with a 48-centimeter-long cathode ray tube displaying a visual stimulus, while the scientists monitored both eyes simultaneously.
During the evaluation, the team found significant changes in smokers' color perception of red-green and blue-yellow color schemes. This finding led the researchers to conclude that the consumption of neurotoxic substances can lead to vision loss. The team also recognized that chain smokers had more difficulty distinguishing contrasts and colors than non-smokers.
"It has long been known that cigarette smoke consists of a variety of pollutants and is associated with a reduction in the brain layers. This also includes lesions in the frontal lobe and reduced activity in the brain region that processes vision," notes study co-author Steven Silverstein. "Previous studies have shown that long-term smoking can double the risk of age-related macular degeneration and play a role in yellowing lenses and inflammation in the eye. Our results are further evidence of the many visual impairments caused by long-term tobacco addiction" Dr. Silverstein added.
The investigations did not provide a physiological explanation for the results. However, Dr. Silverstein emphasizes that nicotine and smoking can damage the blood vessels and neurons in the retina because the pollutants generally enter the vascular system.
The results suggest the need for further investigations into visual processing impairments in other groups. For example, the smoking behavior and its impact on patients with conditions such as schizophrenia should be taken into account.
Thiago P. Fernandes, Steven M. Silverstein, Natalia L. Almeida, Natanael A. Santos. Visual impairments in tobacco use disorder. Psychiatry Research, 2019; 271: 60 DOI: 10.1016/j.psychres.2018.11.024