Preservatives are often added to eye drops to maintain sterility. One of the most common preservatives used in eyedrops is benzalkonium chloride (BAK).
Both in vitro studies and animal studies have found BAK to be toxic to the cornea and that it may exacerbate dry eyes.[1] Additionally, a cross-sectional study of adults with glaucoma found that using BAK-preserved travoprost was correlated with ocular surface disease and decreased quality of life.[2] It’s also not uncommon for people using eye drops to treat glaucoma to experience redness, burning, or irritation after using BAK-preserved eye drops.
On the other hand, a 2019 meta-analysis found that compared to preservative-free or alternative preservative eye drops, using BAK-preserved eye drops resulted in no significant differences in intraocular pressure, conjunctive hyperemia, ocular hyperemia, total ocular adverse events, or tear break-up time in people with glaucoma.[3]
In light of these mixed findings, it’s important to consider context and population when assessing the effects of BAK-preserved eye drops. Most of the research on BAK-preserved eye drops has been studied in people with glaucoma, so it may not be applicable to people with dry eye or other eye conditions.
When treating a specific condition like glaucoma or dry eye, it’s vital to weigh the risks and benefits of using BAK-preserved eye drops. If an individual is not experiencing any adverse effects, the benefits of continuing to use BAK-preserved eye drops may outweigh any potential risks.
Ultimately, if BAK-preserved eye drops cause irritation or exacerbate any symptoms, it may be wise to consider other options, such as preservative-free eye drops. However, this decision must be specific to the individual and done with the help of a qualified healthcare provider.