The Dry Eye Zone

Rebecca's Blog


Glaucoma and dry eye - updates

When I say glaucoma…

I really mean glaucoma medications, and when I say glaucoma medications, I really mean the preservative benzalkonium chloride (BAK) - mostly.


We know this, and we’ve known it for a long time, but why hasn’t it changed clinical practice and pharmaceutical company offerings faster?

How much more evidence do we need of the harmfulness of BAK to people with glaucoma before we phase out BAK-preserved glaucoma medications?


Study #1: Ocular Surface Evaluation After the Substitution of Benzalkonium Chloride Preserved Prostaglandin Eye Drops by a Preservative-free Prostaglandin Analogue.

Lopes et al, Medical Hypothesis, Discovery & Innovation ophthalmology journal, spring 2019

In this study the patients saw an improvement to their dry eye symptoms (measured with OSDI) after JUST SIX WEEKS of switching to a preservative-free drop!

That is good news, of course… that it can get better. They don’t say in the abstract how long the patients had been on a BAK-preserved drop, though.


To evaluate ocular surface changes after withdrawal of Benzalkonium chloride (BAK) in patients with glaucoma in monotherapy with BAK-preserved prostaglandin. This was a prospective observational study. All patients underwent complete ophthalmologic examination and evaluation of ocular surface. A questionnaire was filled regarding symptoms of dry eye (Ocular Surface Disease Index [OSDI]) at the beginning of study. The treatment was switched to preservative-free tafluprost for 6 weeks and after this period, all patients were re-evaluated. All patients reported improvement of symptoms. The green lissamine test showed a significant improvement of the ocular surface, with most patients classified as light dry eye (P < 0.001). A significant improvement in the score (P < 0.001) was also found, with an average of 17.95 ± 5.35 points, which classifies the patients' symptoms in the normal to light zone. Benzalkonium chloride withdrawal reduced the signs and symptoms of dry eye in patients with primary open angle glaucoma (POAG).

Study #2: The impact of topical intraocular pressure lowering medications on the ocular surface of glaucoma patients: A review.

Asiedu et al, Journal of Current Opthalmology

(Hmmm I’ve seen some other really great work by this author on dry eye, depression, QOL etc.)

This is a far-reaching review of dry eye in glaucoma patients using pressure-lowering medications. I love the scope of what they looked at! Hoping to get hold of the full study. I found it very interesting that in addition to everything else, they looked at the pH of the medications.

Bottom line though, it’s not just the preservative, it’s also the active ingredients, that are at fault. However, we have control over preservatives… so we should be exercising that control. It’s just not right that the elderly are so much more subject to these quality-of-life hits just because the industry and doctors are taking so long to come up to speed on the issues.



To assess the literature on the effects of topical intraocular pressure (IOP)-lowering medications on the ocular surface. Ocular surface assessment in these patients is seldom a priority for most clinicians since the ultimate goal of management is to preserve vision.


A literature search of articles (English only) on the subject matter was conducted and their findings summarized.


This review assesses the prevalence of dry eye symptoms in glaucoma patients on topical IOP-lowering medications. We extensively reviewed the effects of the preservatives and active ingredients in these medications on the ocular surface. In particular, the effects of benzalkonium chloride (BAK), a widely used preservative, on meibomian glands are explored. Also mentioned in this review is the association between duration of therapy and severity of dry eye symptoms. The role of the pH of medications in the development of ocular surface disease is also reviewed. Finally, we probed the occurrences of ocular allergic reactions with the use of topical IOP-lowering medications.


The preservatives and active agents in most topical glaucoma medications are implicated in the prevalence of ocular surface discomfort. Whilst clinicians involved in glaucoma care are encouraged to assess the ocular surface routinely, further studies are needed to demonstrate the contributions of other physiochemical properties of these medications to the development of ocular surface disease in these patients.

Study #3: Impact of glaucoma medications and ocular surface disease on the quality of life of glaucoma patients in the district of Sousse (Tunisia)

Leila et al, Journal Francais d’Ophtalmologie, March 2019



To assess the impact of glaucoma treatment and ocular surface disease (OSD) on the vision-specific quality-of-life (VS-QoL) of glaucoma patients attending Farhat Hached university hospital Sousse-Tunisia.


This was a cross-sectional study enrolling one-hundred-twenty patients followed for primary open angle glaucoma. All patients successfully responded to the Arabic version of the National Eye Institute Visual Function Questionnaire 25 (NEI-VFQ 25). QoL was quantified in terms of scores (0-100) and correlated with the characteristics of glaucoma treatment and status of the ocular surface.


One hundred and twenty patients were studied. The mean number of medications and instilled drops was 1.95 (1-4) and 2.69 (1-7) respectively. A total of 66.7% patients reported side effects of treatment. On examination, moderate or severe dry eye syndrome was identified in 90% of cases. A total of 16.7% of patients had superficial punctate keratopathy. The number of instilled drops per day, the use of brimonidine or oral carbonic anhydrase inhibitors, and the presence of OSD had a negative impact on the NEI-VFQ 25 scores.


Glaucoma treatment and OSD are 2 factors potentially reducing the QoL of glaucoma patients, on which the ophthalmologist can act by optimizing treatment and regularly examining the ocular surface of glaucoma patients.