People who quit smoking and then switch to non-combustible nicotine replacement products (such as vaping or other products) have a slightly but consistently higher risk of developing serious eye diseases that affect vision than those who quit completely, according to a large South Korean study.

The study was based on South Korea’s National Health Insurance data, which followed 32,316 former smokers for an average of 4.6 years. Participants were divided into two groups: those who quit completely and those who used alternative nicotine products.

A total of 6,328 new cases were identified during the follow-up. The incidence rate was 41.1 per 1,000 people after 10 years in those who quit completely, compared with 44 per 1,000 people after 10 years in those who used alternative nicotine products.

The analysis of the data showed that users of nicotine replacement therapy had a 7 percent higher overall risk of eye disease. The most significant increases were seen in diabetic retinopathy (24 percent higher risk) and problems with focusing vision.

The study, conducted by Korea University College of Medicine, was published in the American Journal of Ophthalmology.

Experts say the findings suggest that switching to nicotine replacement therapy alone after quitting smoking is not entirely safe, and that a better strategy is to avoid nicotine altogether.