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Glaucoma is a serious condition that warrants close attention and careful management to avoid progression and vision loss. But failure to account for the health of the rest of the eye while attending to glaucoma could be detrimental to the patient’s outcome. In particular, the health of the glaucoma patient’s ocular surface can have implications not only for that patient’s vision, but also for the efficacy of the glaucoma treatment you prescribe.
Glaucoma becomes more prevalent with age, and so does meibomian gland dysfunction (MGD).1,2 Naturally, there is crossover of the patient populations affected by these conditions, and many glaucoma patients are affected to some degree by ocular surface compromise.3,4
This comorbidity is increasingly being recognized because of our improving diagnostic acumen with ocular surface issues. MGD was likely always an issue among glaucoma patients, but improved diagnostics and increased understanding of dry eye disease and its implications for ocular health have expanded the recognition of MGD as an important entity to consider in this population. In this comorbid relationship, MGD can affect the treatment of glaucoma, and the treatment of glaucoma can affect any MGD that may be present.
MGD AND GLAUCOMA TREATMENT
Questions about ocular surface health in respect to glaucoma tend to concern how the ingredients in the topical medication bottle may be harmful to the ocular surface. Less well appreciated may be that tear film insufficiency may affect the efficacy of glaucoma medications—especially if the ocular surface disorder is significant enough to compromise the patient’s adherence to the dosing schedule.
Many medications used in glaucoma therapy contain preservatives. The one that is most concerning for the ocular surface and MGD is benzalkonium chloride (BAK). On the positive side, BAK can disrupt the ocular surface epithelium and potentially improve the penetration of the active ingredient.5,6 However, BAK can also have cytotoxic effects,4 and in an eye with a compromised tear film, the irritating nature of BAK can have deleterious effects on comfort and vision.7,8
In some cases, the active ingredient itself, rather than the preservative, can be the irritating element. One of the side effects of the prostaglandin class of glaucoma drugs is burning upon instillation.9 This may be attributable to a vasodilatory effect of the drug or it may be secondary to an undiagnosed ocular surface insufficiency. Regardless of the mechanism for this side effect, patients take these topical therapies chronically, and their built-up cumulative effect over the course of decades will almost assuredly have an effect on the health of the ocular surface.
Over time, mild MGD is likely to be exacerbated into more severe forms by glaucoma treatment, the net effect being that eye drops that are already irritating become more so. In glaucoma, where patients’ compliance is already a complicated issue, any additional reason for patients to avoid their drops is a concern.
Luckily, in recent years our ability to detect even mild forms of MGD has vastly improved. In addition, a wealth of treatment options for both MGD and glaucoma provides adequate options to design interventions that treat glaucoma while having the least possible effect on the ocular surface.
In our clinic, where technicians do most of the workup before the specialist’s interaction with patients, we have incorporated a suite of useful but easy-to-integrate screening and testing protocols. The Tear Osmolarity Test (TearLab) is an important component of ocular surface management, as it provides a quantitative index for tear film irregularity and instability. If indicated, we can also perform analysis with the LipiView II Ocular Surface Interferometer (TearScience) to detect MGD. During the eye care provider’s examination, a careful slit-lamp examination is performed, during which the meibomian glands are expressed to gauge the quality of the meibum. Thin and olive oil-like expression indicates healthy secretion, whereas thick and toothpaste-like suggests MGD.
We also listen attentively to patients’ recounting of their symptoms. A report of blurry vision, for instance, will lead us to ask when it occurs. If it occurs around the time of instillation of a glaucoma medication, this can indicate a potential issue with the drop or an irregular tear film. If it occurs at other times of the day, MGD may be the more likely cause. Typical signs of MGD such as redness and irritation on the eyelids are also of interest.
Dynamic Meibomian Imaging (TearScience) can also serve a useful role in educating patients about the health of their ocular surface. Serial meibography with this device can occasionally unveil whether there have been changes to the meibomian gland structure as a result of treatment. In addition, repeated imaging demonstrates to patients that the treatment is having an effect, even if their symptoms are not yet alleviated. The benefit of motivating patients to stay on track with their MGD therapy should not be underestimated. Patients need to take an active role in MGD management to achieve greater success.
DO NOT FORGET THE GLAUCOMA
Among the reasons to address MGD in glaucoma patients is that a compromised ocular surface may impair the ability of glaucoma medications to penetrate into the eye. Topical formulations are engineered to penetrate the ocular surface of a healthy human eye with osmolarity of about 290 to 300 mOsm/L. Hyperosmolarity, if present, could yield unknown effects in a drug’s ability to pass through the corneal surface. Thus, treating MGD may be good for the patient’s glaucoma as well.
With regard to adjusting glaucoma treatment in the presence of MGD, there are basically two approaches: to take away factors that may be offending the ocular surface, or to add factors to make the ocular environment better. Patients may benefit from a combination of both. Glaucoma patients should be counseled on good ocular ergonomics when using a computer (looking down instead of straight on, looking away occasionally to blink and refresh the eye). They should be made conscious of the potential for fans and forced air to dry the eye. There may be other exacerbating factors that can be removed as well, such as systemic medications or the use of makeup around the eye.
Generic formulations of glaucoma medications all contain BAK, so an in-class switch to a preservative-free or non-BAK option may be in the patient’s best interest. A fixed-combination medication may be an option if prostaglandin use is undesirable due to tolerability issues or if an additional therapy is needed.
For patients with severe MGD, topical glaucoma therapy may not even be an option, especially if the ocular surface issue is limiting the efficacy of the drops. However, these patients’ glaucoma definitely must be addressed. To achieve intraocular pressure lowering in patients who cannot tolerate topical medications, another intervention strategy may be needed. Selective laser trabeculoplasty with the Selecta II laser (Lumenis) is a consideration, and surgery may be a consideration based on the particulars of the patient. At the very least, if the MGD is interfering with glaucoma therapy, this is a rationale for escalating therapy to a more aggressive approach.
Glaucoma specialists are trained to treat this chronic medical condition aggressively and completely. Getting the intraocular pressure to a safe level is of utmost importance to slow and prevent progression. And yet our patients may have other ocular issues to consider, and those issues may be detrimental to quality of life in addition to being a hindrance to treatment. Coexisting ocular surface disease warrants consideration when a glaucoma treatment plan is devised because the ocular surface issue deserves treatment in its own right. Improving the ocular surface by treating MGD does more than balance and improve the effectiveness of the glaucoma intervention; it may also improve patients’ well-being if it allows them to enjoy the benefits of good vision without compromise. n
1. Moss SE, Klein R, Klein BE. Prevalence of and risk factors for dry eye syndrome. Arch Ophthalmol. 2000;118:9:1264-1268.
2. Friedman DS, Wolfs RC, O’Colmain BJ, et al. Prevalence of open-angle glaucoma among adults in the United States. Arch Ophthalmol. 2004;122:4:532-538.
3. Fechtner R, Budenz, D, Godfrey D. Prevalence of ocular surface disease symptoms in glaucoma patients on IOP-lowering medications. Poster presented at: The 18th Annual Meeting of the American Glaucoma Society; March 8, 2006; Washington, DC.
4. Noecker R. Effects of common ophthalmic preservatives on ocular health. Adv Ther. 2001;18(5):205-215.
5. Majumdar S, Hippalgaonkar K, Repka MA. Effect of chitosan, benzalkonium chloride and ethylenediaminetetraacetic acid on permeation of acyclovir across isolated rabbit cornea. Int J Pharm.2008;348(1–2):175–178.
6. Keller N, Moore D, Carper D, Longwell A. Increased corneal permeability induced by the dual effects of transient tear film acidification and exposure to benzalkonium chloride. Exp Eye Res. 1980;30(2):203–210.
7. Noecker RJ, Herrygers LA, Anwaruddin R. Corneal and conjunctival changes caused by commonly used glaucoma medications. Cornea. 2004;23(5):490-496.
8. Kahook MY, Noecker RJ. Comparison of corneal and conjunctival changes after dosing of travoprost preserved with Sofzia, latanoprost with 0.02% benzalkonium chloride, and preservative-free artificial tears. Cornea. 2008;27(3):339-343.
9. Prum BE, Rosenberg LF, Gedde SJ, et al. Primary Open-Angle Glaucoma Preferred Practice Pattern Guidelines. Ophthalmology. 2016;123(1):P41-P111.
Robert J. Noecker, MD, MBA
• In practice with the Ophthalmic Consultants of Connecticut in Fairfield, Connecticut
• Assistant clinical professor, Yale University School of Medicine,
• New Haven, Connecticut
• Clinical professor of surgery, Netter School of Medicine, Quinnipiac University, North Haven, Connecticut
• Financial disclosure: consultant to Tear Science