The study’s 4,351 subjects, aged 13-24 years, were questioned about their smoking habits and ocular symptoms. Irrespective of the pattern of tobacco product use, most participants reported having no symptoms or mild ocular symptoms, occurring up to three times per month, while dual users reported moderate to very severe ocular symptoms, including severe ophthalmic dryness/gritty sensation and blurriness, said researchers. Dual users were also found to have more frequent ocular symptoms occurring daily or 1 to 6 times per week compared with e-cigarette only or cigarette-only users in each user timeframe.
Writing in JAMA Ophthalmology, researchers noted each form of smoking could be a risk factor for dry eye disease, but with differing mechanisms. Combustible cigarette puffs’ free radicals increase oxidative stress and inflammation, which can damage the tear film lipid layer, they said, citing a study hypothesising vape solvent (propylene glycol) generates free radicals destroying the lipid layer of tear film via lipid peroxidation. However, more study is warranted, said researchers, noting a 2019 study concluded that mild exposure to e-cigarettes did not significantly affect the corneal epithelial thickness and non-invasive keratography tear break up.