Benzalkonium Chloride (BAK)

“BAK is bad for the conjunctiva, the cornea and perhaps even the trabecular meshwork,” said John R. Samples, MD, professor of ophthalmology at the Oregon Health & Science University in Portland. “It is a toxic detergent. It attracts monocytes and lymphocytes into the conjunctiva and it makes the tissue thicken up.”

Dr. Samples contends that BAK can have negative consequences that extend from the ocular surface all the way to the posterior pole. “BAK makes dry eye worse in some patients; it is toxic to corneal epithelial cells and, according to our laboratory work, it is toxic to corneal endothelial cells and trabecular cells when it enters the anterior chamber; it gives us a dysfunctional conjunctiva when it comes time to consider filtration; it has a complex role in setting up allergic reactions in the eye. It has even been implicated in the occurrence of cystoid macular edema,” he noted.

“BAK is a mixed bag,” said Richard A. Lewis, MD, glaucoma specialist in Sacramento, Calif., and former president of the American Glaucoma Society.

“The greater the exposure to the preservative, the greater the effect and that effect is cumulative. There are a lot of dry eye problems with BAK,” he said. “There are eyelid and conjunctival problems, irritation and redness, with the whole ocular surface affected by these preservatives.” He finds it affects tear function and that even minor exposure may induce cell-growth arrest and death by necrosis or apoptosis.


Glaucoma eyedrops: a fresh look at preservatives
Phillips P.
EyeNet Magazine
January 2008. Retrieved October 19, 2015.
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