Due to the frequent coexistence of ocular surface disease and glaucoma in older patients, clinicians should take steps to reduce the potentially damaging effects on the ocular surface of long-term use of glaucoma medication. Reducing the number of medications when possible and choosing those that do not contain the preservative benzalkonium chloride is an approach that may be beneficial in some patients.
Denver-Numerous prevalence studies have shown that dry eye or ocular surface disease (OSD) affects a considerable number of adults. Although estimates vary widely, depending on how OSD is measured, most studies indicate that it affects at least 10% to 12% of the adult population.
Estimates of glaucoma prevalence also differ but seem to top out at about 5% of adults. Since the prevalence of glaucoma and dry eye disease increases with age and both are chronic conditions, a therapeutic approach that minimizes the impact of glaucoma therapy on the ocular surface is of great importance in everyday practice, said Malik Kahook, MD, assistant professor of ophthalmology and director of the glaucoma service at the University of Colorado Denver.
Dr. Kahook is among the physicians who have conducted studies evaluating the effects of BAK in animal models as well as in glaucoma patients. He recently reported on studies in an animal model indicating that medications preserved with BAK may lead to loss of goblet cells as well as loss of cell to cell adhesions, which may predispose patients to having ocular surface damage. Once-daily dosing of latanoprost with 0.02% BAK (Xalatan, Pfizer) produced more goblet cell loss compared with either travoprost (Travatan Z, Alcon Laboratories) with an ionic-buffered preservative system (sofZia, Alcon) or a preservative-free artificial tear. He cautioned that these data must be confirmed in human patients to understand better the significance of the findings.
Dr. Kahook also conducted a study on changes in TBUT and the Ocular Surface Disease Index (OSDI) after treatment was switched from latanoprost to travoprost with the preservative system.
"We found an improvement in TBUT from an average of around 2 seconds to an average of around 6 seconds," Dr. Kahook said. "What's more important is that we found a relationship between the improvement in TBUT and the improvement in OSDI score, so it wasn't just an objective result. Subjectively, the patients felt better."
The limitations of this study include its setting in Denver, a locale that has an arid climate, and in a tertiary care center where many patients had severe dry eye.
"Perhaps we were more likely to see a change just by switching one medication, whereas such a phenomenon might not be noticed if somebody were to do this study in Florida, where the humidity is higher," Dr. Kahook said. "In order to validate these results there would have to be a multicenter study, the investigators would have to be masked to the study medication, and you would need a control group."
Dr. Kahook said that when he sees patients who have significant OSD and are using one or more medications containing BAK, switching treatment to IOP-controlling drops that do not contain this preservative seems to improve their symptoms.
Because BAK is only one of many factors involved in OSD, however, a change in medication alone may make only a small difference in symptoms in some patients.
"You might have to help them out with other measures, including a mild steroid such as loteprednol etabonate ophthalmic suspension 0.5% [Lotemax, Bausch & Lomb] or fluorometholone or topical cyclosporine A [Restasis, Allergan], which we tend to use regularly in our dry climate, and we have noticed a significant improvement in our patients," Dr. Kahook said.