Vaping poses unexpected risks to eye health, study finds

A study published in the Journal of Clinical Medicine finds that the use of electronic cigarettes (E-cigarettes) is associated with non-intended and intended ocular surface exposures.

Systematic Review: The Impact of Vaping on the Ocular Surface: A Systematic Review of the Literature. Image Credit: Flystock / Shutterstock

Background

The use of E-cigarettes and other vaping products has increased globally in recent years due to the general perceptions about their less harmful health outcomes compared to conventional combustible tobacco cigarettes. According to the 2020 estimates, about 68 million people use E-cigarettes worldwide.

Existing literature on E-cigarette-related safety issues has highlighted its potentially harmful effects on the respiratory system, including acute respiratory distress syndrome and acute eosinophilic pneumonia.

Some recent studies have shown that nicotine and other chemicals in E-cigarettes can affect different eye components, including the corneal epithelium, the tear film, and retinal light-adapted vision. These chemicals can also exert vasoconstrictive effects on ocular blood flow.

In this systematic review, authors have comprehensively analyzed existing studies investigating the impact of E-cigarettes and vaping products on the ocular surface.

Study design

The authors thoroughly searched various electronic databases and identified 18 studies that investigated the impact of E-cigarette or vaping product use on the ocular surface in humans. They thematically analyzed these studies to identify non-intended exposures and intended exposures separately.

In non-intended exposures, study participants were unexpectedly exposed to E-cigarette or vaping product components. Participants were aware of their E-cigarette or vaping product use in intended exposures.

Non-intended exposures

Non-intended exposures are typically caused by explosions or any kind of damage to E-cigarettes or vaping products that unexpectedly expose the users to E-liquid or any other components.

Existing evidence regarding ocular injuries indicates that E-cigarette explosions can cause corneal injury, subconjunctival hemorrhage, and deposition of black particulate in the tear film and conjunctiva.

A wide variation in the severity of these injuries has been documented, including severe corneal abrasion, superficial upper eyelid laceration, conjunctival laceration, traumatic mydriasis, eye inflammation, traumatic retinopathy, and acute traumatic maculopathy (Berlin’s edema).

Regarding non-intended exposure to E-liquid, evidence indicates a variety of consequences, ranging from mild eye irritation to ocular chemical injury.

In the United States, about 87% of calls to poison control centers have been found to be associated with non-intended ocular surface exposures to E-cigarettes or vaping products.    

Intended exposures

Intended ocular surface exposures to E-cigarettes or vaping products are associated with both acute and chronic consequences.

Regarding acute exposure, a study involving 64 participants has found that ocular surface exposure to E-cigarettes at a dose equivalent to 10 puffs can alter tear film stability and increase corneal epithelial thickness.

Several detrimental consequences of chronic exposure have been reported, including ocular surface malignancies, alteration in tear film stability and quality, tear production and corneal epithelial thickness, loss of upper and lower eyelid meibomian glands, and dry eye symptoms or ocular irritation.  

Regarding ocular malignancies, evidence indicates that long-term exposure to carcinogenic components of E-cigarettes might be responsible for the development of conjunctival intraepithelial neoplasia.

A significant alteration in tear film stability and quality and subsequent dry eye or eye irritation have been observed among long-term E-cigarette users.

Regarding tear production, one study found almost 2-fold higher tear production among E-cigarette users compared to non-users, which might be a homeostatic measure in response to impaired tear film integrity. In contrast, another study has pointed out that E-cigarette use is associated with a reduction in tear production, which might be attributed to the changes in the ocular surface caused by E-cigarette-induced lipid peroxidation.

Regarding the meibomian glands, evidence indicates that long-term E-cigarette exposure can lead to a significant average loss of the gland in both upper and lower eyelids. Moreover, E-cigarette users have been found to have irregularly distributed and less hyperreflective meibomian glands.

Regarding dry eye symptoms, evidence indicates that the severity of dry eye syndrome increases with the induction in E-cigarette voltage.

Study significance

This systematic review finds that exposure of the ocular surface to E-cigarettes or vaping products can have serious consequences. A lack of information regarding the long-term impact of E-cigarette use on the ocular surface highlights the need for well-designed future studies.