Heavy Smoking May Lead to Significant Colour Vision Loss

A new Rutgers study shows smokers have reduced the ability to discriminate contrasts and colors.

People who smoke more than twenty cigarettes a day are likely to experience significant color-vision loss a new report, co-authored by Rutgers suggests. The study examined 71 healthy people who smoked fewer than 15 cigarettes in their whole lives in comparison to 63 who smoked more than 20 cigarettes a day. 

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Members of the latter group were diagnosed with tobacco addiction and were currently still smoking with no reported attempt to quit. All participants were aged between 25 and 45 had a normal or corrected-to-normal vision as measured by standard visual acuity charts. 

The participants had both their eyes monitored simultaneously as they watched stimuli presented on a 19-inch cathode-ray tube monitor placed 150 centimeters away from them. 

Smoking directly affects frontal lobe

The researchers were looking at how the participants discriminated contrast levels (subtle differences in shading) and colors displayed in the stimuli. The findings found significant differences in the smokers' red-green and blue-yellow color vision, which suggests the neurotoxic chemicals found in cigarettes may cause overall color vision loss. 

The smokers also had a reduced ability to discriminate contrasts and colors when compared to the non-smokers. 

"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," said co-author Steven Silverstein, director of research at Rutgers University Behavioral Health Care. 

Visual processing strongly affected by ongoing smoking

"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. 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." 

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The study did not present the psychological reasons for how vision loss is caused. But as ingesting nicotine and smoking is known to harm the human vascular system, it is also likely to damage to blood vessels and neurons in the retina is the source of the vision loss. 

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Cigarette smoke is comprised of numerous compounds that have been found to be harmful to health. The effects of inhaling cigarette smoke include a reduction in the cortical thickness. 

In the USA smoking is the cause of about 90% of all lung cancer deaths. It is also the leading cause of deaths from chronic obstructive pulmonary disease (COPD). The research appears in the journal Psychiatry Research.

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