The Dry Eye Zone

Rebecca's Blog

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Glaucoma drop study - another nail in the BAK coffin... right?

I enjoyed reading this study titled "Exploring topical anti-glaucoma medication effects on the ocular surface in the context of the current understanding of dry eye" (scroll down for the abstract)

On the face of it, it is all about glaucoma drops and dry eye. But don't be fooled by the absence of the word "preservative" in the text of the abstract. I checked with the authors to verify a few details because the complete text had not yet been released. As suspected, the paper is really mostly about the known and despised toxic effects of the preservative benzalkonium chloride (BAK), also known as dry eye inducing poison for your eyes.

There is a plethora of literature on the toxic effects of BAK to the cornea. Much of the attention has been given to BAK in the context of glaucoma medication. This is presumably because glaucoma patients (1) have to take drops every day for years, which means long term exposure to the risks, and (2) are older, which means they are already at higher risk, even without additional risk factors common in their age group, such as cataract surgery and the many health conditions requiring medications that are known to be drying to the eyes. Why would we put people to this kind of long term completely avoidable risk? On the other hand, there's probably a much simpler reason for the proportionally high attention to glaucoma drops: (3) glaucoma patients are relatively easy to study as there's so many of them, and they have to take the drops. Bit of a captive audience.

In relatively recent years, preservative free glaucoma medications began seeping onto the market and - much too slowly - began displacing the preserved ones. I remember the first PF glaucoma drop - Travatan Z - and how long it took before I ever heard from dry eye patients whose doctors prescribed it without specifically being asked to by the patient. (You'd think the glaucoma doctors and the cornea doctors might at least occasionally chat over a water cooler?) Thankfully, things are much better now than they were. - That is, specifically in the world of glaucoma medications, and specifically in the US. (Dr Craig mentioned that no preservative free publicly funded options are available yet in New Zealand.)

One of the areas I continue to be very, very concerned about when it comes to dry eye and corneal damage from BAK overexposure is in over-the-counter eyedrops in the US. Drugstore shelves are crammed with all kinds of BAK preserved drops, ranging from lubricants to antihistamines to vasoconstrictors - plus, my most hated crowd: the combo multi-purpose drops. A little bit of lubricant, a vasoconstrictor, an antihistamine, pick a random collection of benefits, stir them up and put a pretty label on them. The majority of such drops are preserved with BAK and as such they pose serious risks to people who buy them and use them regularly.

To me this is a painful failure on the part of the FDA as the warning language in the packaging is completely inadequate. Drops that promise relief of irritation and redness should not contain substances that are known to cause harm if you continue using them. Many of the people these drops are marketed to rarely visit an eye doctor because the level of eye irritation is not severe. There is no one to tell them they are in harm's way.

Anyway, circling back to glaucoma: If you are using glaucoma drops, and you do not know whether they are or aren't preserved, please find out, and talk to your doctor about whether there are preservative free alternatives that would be appropriate for you.

Ocul Surf. 2018 Mar 3. pii: S1542-0124(17)30311-7. doi: 10.1016/j.jtos.2018.03.002. [Epub ahead of print] 
Exploring topical anti-glaucoma medication effects on the ocular surface in the context of the current understanding of dry eye.
Wong ABC1, Wang MTM1, Liu K1, Prime ZJ1, Danesh-Meyer HV1, Craig JP2
Abstract
PURPOSE:
To assess tear film parameters, ocular surface characteristics, and dry eye symptomology in patients receiving topical anti-glaucoma medications. 
METHODS:
Thirty-three patients with a diagnosis of open angle glaucoma or ocular hypertension, receiving unilateral topical anti-glaucoma medication for at least 6 months, were recruited in a cross-sectional, investigator-masked, paired-eye comparison study. Tear film parameters, ocular surface characteristics, and dry eye symptomology of treated and fellow eyes were evaluated and compared. 
RESULTS:
The mean ± SD age of the participants was 67 ± 12 years, and the mean ± SD treatment duration was 5.3 ± 4.4 years. Treated eyes had poorer non-invasive tear film break-up time (p = 0.03), tear film osmolarity (p = 0.04), bulbar conjunctival hyperaemia (p = 0.04), eyelid margin abnormality grade (p = 0.01), tear meniscus height (p = 0.03), and anaesthetised Schirmer value (p = 0.04) than fellow eyes. There were no significant differences in dry eye symptomology, meibomian gland assessments, and ocular surface staining between treated and fellow eyes (all p > 0.05) 
CONCLUSIONS:
Adverse changes in tear film stability, tear osmolarity, conjunctival hyperaemia, and eyelid margins were observed in treated eyes. This suggests that inflammatory mechanisms may be implicated in the development of dry eye in patients receiving long term topical anti-glaucoma therapy.