A major US study has found that e-cigarettes harm users' eyesight, casting doubt on claims that the devices are a safe alternative to smoking.
Current vapers were 34% more likely to have impaired vision from those who had never tried it, and former vapers were 14% more likely.
The solvents in e-cigarette liquid, according to researchers, may damage the tear duct and also cause "oxidative stress" in the body, which has been linked to ocular degradation.
Traditional cigarettes have long been known to be harmful to people's vision.
Even so, in the United Kingdom, e-cigarettes have been promoted as somehow being considerably safer, with the government claiming they are at least 95% less harmful.
Despite health officials' advice that the devices must only be used by regular smokers to help them quit, their popularity has skyrocketed, particularly among the young.
As per the campaign group Ash, the rate of e-cigarette users increased from around 700,000 in 2012 to 3.6 million in 2019, then fell to 3.2 million in 2020 before rising to 3.6 million in 2021.
The World Health Organization declared e-cigarette use to be a "epidemic" last year.
The new study by the University of California was designed as a snapshot survey, with 1,173,646 adults in the United States aged 18 to 50 participating. They were asked in a questionnaire between 2016 and 2018 if they smoked, vaped, or had any visual impairment. The findings appear in the American Journal of Ophthalmology.
E-cigarettes produce an aerosolized liquid that contains nicotine, flavorings, and solvents like propylene glycol or glycerin.
But since traditional cigarettes is chemically complex – the smoke contains over 4,000 chemical elements – scientists have struggled to determine what causes vision damage.
A Malaysian study published in 2019 found a link between e-cigarette use as well as increased symptomatic dry eye and weakened tear film quality.
The authors hypothesized that the propylene glycol solvent in the vape liquid generates free radicals that harm the tear film's lipid layer. The researchers discovered that the vapers in the study had high levels of reflex tearing.
Another notion is that e-cigarettes cause oxidative stress and a decrease in antioxidants, both of which have been involved in the formation of cataracts, age-related macular degeneration, and even glaucoma.
"There is a clear association between smoking lit cigarettes and visual impairment," said Professor Simon Capewell, a clinical epidemiologist at the University of Liverpool who was not involved in the new study. "There are also many nasty toxins in e-cig vapour." He added.
"It will therefore be important for doctors and other researchers to carefully assess the onset of new visual impairment in vapers, especially those who have never used lit cigarettes."
He remarked that the study did not establish a cause and effect relationship between vaping and vision damage.
Scientists at Virginia Commonwealth University criticized Public Health England's 95% claim in 2020 as misguiding and out of date, owing to increased changes in e-cigarette technology.
The UK government is largely viewed as a foreign outlier in terms of its enthusiasm for vaping as a method of smoking cessation.
Supporters claim that the strategy has increased the number of people withdrawing tobacco while guaranteeing that vape products are not directly marketed to children.
According to a study published last year, E-cigarettes are also associated with substantial adverse cardiorespiratory and immunological changes, with reports proving that the devices raise blood pressure, heart rate, and arterial stiffness.