A new study suggests that smoking can impair vision far earlier than is commonly thought.

Heavy smokers with an average age of 35 were markedly worse than nonsmokers at distinguishing colors as well as the contrast between different shades of gray, reported the study authors.

The new results, published in Psychiatry Research, do not indicate how smoking damages perception of color and contrast.

Co-author Steven Silverstein, a professor of psychiatry and ophthalmology at Rutgers Robert Wood Johnson Medical School, said cigarette use likely harms a general aspect of vision biology such as blood vessels or nerve cells.

Study participants included 63 people who said they smoked more than 20 cigarettes a day and scored above seven on a 10-point nicotine dependence scale.