Glaucoma: What's next?

The future of glaucoma medical therapy is contingent upon something we all have been concerned about for years, but have never fully addressed: the correlation of ocular surface disease (OSD) and glaucoma.

Due to the close proximity of structures, diseases often overlap - with symptoms of one disease often promulgating symptoms of another. An example of this circular issue is OSD and glaucoma. One condition invites the other, because some topical glaucoma treatments may cause or exacerbate OSD symptoms, yet alternatively, preexisting dry eye, which shares symptoms of OSD, can complicate glaucoma management.¹

Therefore, it is no surprise that studies have shown that up to 66% of subjects with severe OSD also have glaucoma, while other estimates note that nearly 60% of medically treated patients with glaucoma reported OSD symptoms.^2,3

For years, the debate has raged over whether to take the preservative, soft preserved, or non-preserved route, because we have all been concerned with the potential for worsening OSD in our patients, and have taken steps to minimize this if necessary. Unfortunately, we have far too often been focused on minimizing, rather than treating, the OSD.

Prolonged use of topical ocular medications preserved with benzalkonium chloride (BAK) may induce symptoms and signs associated with OSD and have damaging effects on the conjunctiva and cornea. The use of preservative-containing eye drops has been implicated in the development or worsening of OSD, both in vitro and in vivo.^4,5

Further, one study showed that BAK-containing eye drops were associated with approximately two times the likelihood of abnormal results on a lissamine green staining test.³

It has also been demonstrated that the severity of OSD symptoms is positively correlated with the number of IOP-lowering medications used.

A prospective observational study⁶ enrolled patients with primary open-angle glaucoma or ocular hypertension who were taking a regimen of topical IOP-lowering medication. More than 630 patients from 10 sites participated, and results showed that mean Ocular Surface Disease Index (OSDI) scores varied significantly with the number of topical IOP-lowering medications used, with higher OSDI scores in patients using multiple IOP-lowering medications.

In addition, one prospective, double-masked, randomized comparison study⁷ sought to determine the short-term comfort after a single dose of BAK-free travoprost compared with latanoprost in patients with primary open-angle glaucoma or ocular hypertension. Results showed that in 54 subjects who completed the study, no difference in comfort between latanoprost and BAK-free travoprost existed on the visual analog scale 5 seconds after dosing.

Therefore, a preservative-free or BAK-alternative is a great option for treating patients with glaucoma.

Thinking broadly

When glaucoma and OSD co-exist, we are faced with a tough treatment challenge. However, the time has come to stop focusing on localized problems of the eye, but to think broadly.

Eye-care practitioners must ask themselves, how often am I evaluating the patient's ocular surface, which may be of more immediate concern for the patient's comfort, before treating the more slowly progressive but potentially blinding condition, glaucoma?

Managing OSD in patients with glaucoma is not a short-term issue, and it requires a long-term focus on the overall health of the eye as well as a thorough and customized understanding of the individual patient's symptoms and medical history. OSD tests should be utilized prior to glaucoma treatment, if at all possible, because glaucoma screening and evaluation can prevent the physician from accurately assessing the overall picture.

In treating patients with glaucoma who are already taking medications, it is essential to find the best treatment for their OSD and to ensure that their regimen will encourage adherence. Adverse effects have been reported to be the third most common reason for poor compliance in patients with glaucoma.⁸

When evaluating patients, comfort and quality of life are of the utmost importance to a treatment regimen, because noncompliance can produce a host of problems, the most worrisome being glaucoma progression due to lack of treatment efficacy. Though BAK has proven to be a superior antimicrobial, drug contamination has been found most likely to come from patient behavior rather than from the formulations, regardless of whether they contain BAK.⁹ Use of a BAK-free product in single-dose containers can counteract the loss of a preservative while increasing allaround compliance due to less irritation and OSD symptoms.