SEP 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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64 EW CORNEA September 2013 Pharmaceutical focus ABCs of OTC artificial tears by Maxine Lipner EyeWorld Senior Contributing Writer Lissamine green staining in a patient with Sjogren's syndrome. Such patients often rely on artificial tears to help alleviate symptoms. Fingertip with a drop of lubricant about to be placed on the nasal canthus, in the region of the caruncle Source: Minas Coroneo, MD Source: Stephen C. Pflugfelder, MD A foray into the over-thecounter (OTC) artificial tear aisle of any major drugstore can be a daunting experience for dry eye patients going it alone. With what must seem like a jumble of ingredients, there's no telling what distinguishes these. Or is there? Several leading practitioners told EyeWorld what to look for here. Having a roadmap is important for patients because a hit-or-miss trial can be pricey, said Stephen C. Pflugfelder, MD, professor of ophthalmology, Baylor College of Medicine, Houston. "Especially if they're using preservative-free drops, it's going to cost them a minimum of $15, if not $30," Dr. Pflugfelder said, adding that is just for one bottle. Key ingredients At the base level, Dr. Pflugfelder said, artificial tears are regulated by an FDA monograph that allows manufacturers to use a number of different ingredients. Some of these approved agents include polyvinyl alcohol, carboxymethylcellulose, and hydroxypropyl methylcellulose. These have a range of viscosities, with patients having differing points of view on comfort. "For instance, polyvinyl alcohol, which has been around for a long time, is pretty thin and non-viscous, and a lot of patients like that," Dr. Pflugfelder said. "If given a choice between a viscous artificial tear and a non-viscous polyvinyl alcohol tear, probably 50% of my patients would go with the polyvinyl alcohol." He observed that the first preservative-free artificial tears, which came out in the 1980s, the popular Refresh Tears (Allergan, Irvine, Calif.), were polyvinyl alcohol. Today, Refresh Lubricant Eye Drops (Allergan) continue to include this. Still, Dr. Pflugfelder has other patients who prefer Celluvisc Tracking continued from page 61 Cytomegalovirus-positive corneal stromal edema with keratic precipitates after penetrating keratoplasty: A case control study. Cornea. 2013;32:1094-1098. 3. Anshu A, Chee SP, Mehta JS, Tan DT. Cytomegalovirus endotheliitis in Descemet's stripping endothelial keratoplasty. Ophthalmology. 2009;116:624-630. 4. Koizumi N, Suzuki T, Uno T, et al. Cytomegalovirus as an etiologic factor in corneal endotheliitis. Ophthalmology. 2008;115:292-297. Editors' note: The physicians have no financial interests related to this article. Contact information Hannush: 215-752-8564, sbhannush@gmail.com Chee: 65-6227-7255, chee.soon.phaik@snec.com.sg Tan: 65-9818-1962, Donald.tan.t.h@snec.com.sg (Allergan), which contains 1% carboxymethylcellulose and that, he noted, could be the most viscous tear. "Patients think that it hangs around in their eye, and it makes them feel better," he said. Unfortunately, he added, there's usually no telling which patient will prefer which drop. Likewise, the Refresh Optive (Allergan) line also uses carboxymethylcellulose but in addition has osmoprotectants such as L-carnitine and erythritol. "They help to blunt the effect of high osmolarity on cells by preventing them from shrinking and getting inflamed," he explained. As Michael A. Lemp, MD, clinical professor of ophthalmology, Georgetown University, and George Washington University, Washington, D.C., explained it, the approach taken with these osmoprotectants was to mimic the protective mechanisms found in animals who reside in adverse osmolar environments. "They found that some animals absorb certain solutes that go into the cells, attract water, and retain it inside the cells," Dr. Lemp said. Another tactic tried is to combine other artificial tear ingredients with a lipid that would retard evaporative tear loss, Dr. Lemp added. One product incorporating this technique is Soothe (Bausch + Lomb, Rochester, N.Y.). "[The company) believes that when they put a lipid in the eye, the formulation will divide into layers in the tears of the tear film, augment whatever remains of the oil gland secretion there, and form a thicker lipid layer on the tear film and retard evaporation," Dr. Lemp said. Likewise, Dr. Pflugfelder noted that Systane Balance (Alcon, Fort Worth, Texas) contains mineral oil. Meanwhile, the rest of the Systane line, he noted, contains an HP-guar additive. "It's a bean protein that increases the viscosity and binds to the cornea," Dr. Pflugfelder said. Tamping down tear film osmolarity, thought to have a better effect on the ocular surface, is another approach taken to relieve dryness. "Tears containing hyaluronic acid will lower the tear film osmolarity," Dr. Lemp explained. "If you use the drop on a regular basis over several months and then you measure the osmolarity a day after you put any drops in at all, it will still be down." He said that hyaluronic acid is also a very hygroscopic molecule. "It has water molecules hanging on to it," he said. "So for every molecule of hyaluronic acid you're bringing a lot of molecules of water to the surface of the eye." Blink Tears (Abbott Medical Optics, Santa Ana, Calif.) for a long time was the only one to contain hyaluronic acid, Dr. Pflugfelder said, adding that now Oasis Tears (Oasis Medical, Glendora, Calif.) does as well. Another property of hyaluronic acid is that it thins when patients blink, so even though a hyaluronic acid containing tear may be viscous, patients tend not to mind. How big a difference do such ingredients make? Minas T. Coroneo, MD, professor and chairman, Department of Ophthalmology, University of New South Wales, Sydney, Australia, recently conducted a small in-house study comparing various tears. "We used one that was hypotonic, one that had hyaluronic acid, and the third was an ordinary one," Dr. Coroneo said. "We didn't show much difference in staining of the cornea or the tear breakup time." Dr. Coroneo terms this disappointing, but not surprising. "One of the reasons I think there are so many products out there is that the ideal lubricant has yet to be developed, and there isn't one that has beaten the rest of the market," he said. He points to autologous tears as

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