The Impact of Preservatives on the Ocular Surface in Patients with Ocular Hypertension or Glaucoma

The rising prevalence of Ocular Surface Disease (OSD) in patients with glaucoma is an important issue that deserves special attention.

The Impact of Preservatives on the Ocular Surface in Patients with Ocular Hypertension or Glaucoma

 

The rising prevalence of Ocular Surface Disease (OSD) in patients with glaucoma is an important issue that deserves special attention. Maintaining the health of the ocular surface in these patients and preventing OSD, in addition to controlling intraocular pressure, must be a major priority in patient care.

Although glaucoma is not commonly classified as a surface eye disease, studies have shown that 30% to 70% of glaucoma patients experience some degree of ocular surface involvement—a much higher rate than the 5% to 30% seen in populations without glaucoma. It is important to note that OSD is not merely a source of discomfort; it is also associated with an increased risk of failure in glaucoma surgeries.

Several factors play a critical role in the development of OSD, including advancing age, genetics, gender, and systemic comorbidities. Many patients may already have OSD prior to the initiation of topical therapy, which can worsen with treatment. Multiple studies have indicated that up to 59% of patients develop OSD after starting topical glaucoma medications. The number of medications, frequency of administration, and duration of treatment are also major factors influencing the severity of OSD.

The Role of Preservatives

Preservatives are added to ophthalmic drops to prevent microbial contamination. While this practice helps ensure drug sterility, there is substantial scientific evidence that these substances—especially Benzalkonium Chloride (BAK)—have considerable negative effects on the ocular surface.

Benzalkonium Chloride (BAK), which is even used as a general disinfectant, is present in 70% of ophthalmic drop formulations. Research has shown that continuous or cumulative use of Benzalkonium Chloride (BAK) is associated with increased ocular surface toxicity, tear film instability, reduction in goblet cells, disruption of the corneal epithelial barrier, and even injury to deeper structures such as the trabecular meshwork.

Patients using drops containing Benzalkonium Chloride (BAK) often report symptoms such as pain, burning, dryness, itching, and irritation, and score higher on the Ocular Surface Disease Index (OSDI). These side effects can reduce patient adherence to treatment, with up to 60% of patients becoming nonadherent or irregular in their use of medication.

While most generic glaucoma medications contain Benzalkonium Chloride (BAK), preservative-free formulations are now available. These newer drops are significantly less cytotoxic than those containing Benzalkonium Chloride (BAK), lead to a reduction in OSD symptoms, improve patient adherence, and control intraocular pressure effectively, without any loss of therapeutic efficacy.

Given that preservative-free drops (free from substances like Benzalkonium Chloride (BAK)) are now readily available and equally effective, it is recommended to prefer them to maintain ocular surface health, enhance treatment compliance, and reduce complications.

In conclusion, patients should be fully informed about preservative-free options, especially the risks associated with Benzalkonium Chloride (BAK), so they can make knowledgeable choices and protect their ocular surface.

References:

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  2. Chamard C, Larrieu S, Baudouin C, Bron A, Villain M, Daien V. Preservative-free versus preserved glaucoma eye drops and occurrence of glaucoma surgery. A retrospective study based on the French national health insurance information system, 2008-2016. Acta Ophthalmol. 2020;98(7):e876-e881. doi:10.1111/aos.14410

  3. Mylla Boso AL, Gasperi E, Fernandes L, Costa VP, Alves M. Impact of ocular surface disease treatment in patients with glaucoma. Clin Ophthalmol. 2020;14:103-111. doi:10.2147/OPTH.S229815

  4. Harasymowycz P, Hutnik C, Rouland JF, et al. Preserved versus preservative-free latanoprost for the treatment of glaucoma and ocular hypertension: a post hoc pooled analysis. Adv Ther. 2021;38(6):3019-3031. doi:10.1007/s12325-021-01731-9

  5. Thygesen J. Glaucoma therapy: preservative-free for all? Clin Ophthalmol. 2018;12:707-717. doi:10.2147/OPTH.S150816

  6. Goldstein MH, Silva FQ, Blender N, Tran T, Vantipalli S. Ocular benzalkonium chloride exposure: problems and solutions. Eye (Lond). 2022;36(2):361-368. doi:10.1038/s41433-021-01668-x

  7. Zhang X, Vadoothker S, Munir WM, Saeedi O. Ocular surface disease and glaucoma medications: a clinical approach. Eye Contact Lens. 2019;45(1):11-18. doi:10.1097/ICL.0000000000000544

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