Smoking 20 or more cigarettes a day can damage your vision and your ability to see colours, a study has found.

The research, led by Rutgers University in New Jersey, USA, involved 135 healthy people aged between 25 and 45. Researchers tested how well participants who smoked more than 20 cigarettes and those who did not smoke could see contrast levels and colours while sat in front of a screen. It was discovered that smokers did not see as much difference between the colours compared to non-smokers and that there were also changes in smokers’ red-green and blue-yellow vision.

Dr Steven Silverstein, co-author and director of research at Rutgers University Behavioral Health Care, said: ‘Cigarette smoke consists of numerous compounds that are harmful to health. 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.’