Eyeworld

The only negative side effect re- ported was a dimming effect noticed by some in the beginning. "But that tends to fade away as you get used to the drop," he said. Dr. Kim views this pharmaco- logic approach as having a host of advantages over surgical correction of presbyopia. "The reversibility as- pect is huge," he said. "If you don't want the effect, you just stop the drop." He also considers this to be of considerably lower risk than surgery because it is simply a drop. "We're not talking about any incision in the eye—no surgery at all," Dr. Kim said, adding that there's not even laser or thermal treatment involved. Most of the surgical treatments for presbyopia have side effects, includ- ing limited efficacy for this condi- tion, which progresses with age. With a treatment such as conductive keratoplasty, patients end up with regression. "You're not going to see those issues with a drop like this," Dr. Kim said. If all goes well in the ongoing Phase 2b clinical trials, he hopes PRX-100 will be available in about 2 years. Softening the lens Another drop, EV06 (lipoic acid choline ester, Novartis, Basel, Swit- zerland), uses a different approach, according to Richard Lindstrom, MD, adjunct professor emeritus, University of Minnesota, Minneap- olis. The idea with this drop is to soften the natural lens. "What hap- pens as the natural lens ages is that it crosslinks," Dr. Lindstrom said, adding that alpha-lipoic acid in the drop functions as an anti-crosslinker. It uncrosslinks collagen and makes the tissue more elastic, he explained. The idea with this is to restore natural accommodation. "We've known for years that even in a 70- or 80-year-old, when someone looks at a near target, the ciliary muscles are still working," Dr. Lindstrom said. "Those muscles are still attached to the lens, it's just that the lens has become inelastic, so it doesn't change shape." from refractive surgery, Dr. Kim said. "There are so many times a patient with a visual defect will say, 'I can see through that pinhole and that's the vision that I want,'" he said, adding that the drop produces such effects for patients with pathology. PRX-100 acts within 30 min- utes and has a duration of more than 5 hours. Preliminary clinical data from a pilot study performed by David Castillejos, MD, Tijuana, Mexico, on those with presbyopia was promising. In the trial of about 20 presbyopic patients, investigators saw marked improvement in near vision, Dr. Kim noted. They looked at corrected near visual acuity at 14 inches and found that after instilling the drop, there was one to five lines of improvement in patients' near visual acuity. "I was impressed with how much near vision these patients had. I've tried it myself and there is definitely a 'wow factor,'" Dr. Kim said. North Carolina. "It has a propri- etary mixture of two components, the combination of which results in miosis of the pupil without the accommodative effect," he said, add- ing that agents such as pilocarpine also affect the ciliary muscle, but with a downside of blurred distance vision and other side effects such as brow ache. "The difference with this drop is that it totally disassociates miosis from the accommodation," Dr. Kim said. "So you only get a true pinhole effect." The pinhole effect is a power- ful remedy for presbyopia. "In any miotic pupil, you have an increased depth of field," he explained, adding that near vision is markedly im- proved and sometimes even dis- tance vision is as well. Because the pinhole effect also has the potential to reduce light scatter and glare, this makes PRX-100 a viable possibility for therapeutic use as well, including in patients who have corneal scars or who have had complications What drops can do I t's one of the holy grails of ophthalmology: finding a way to restore near acuity to aging eyes without sacrificing distance vision. While many ophthal- mologists have looked strictly to the surgical route for answers, some are now investigating pharmacologic approaches, which they think could be key to more safely solving the problem of presbyopia. EyeWorld took a closer look at two different pharmacologic approaches on the cusp of potentially changing the world of presbyopia. True pinhole effect One of these two pharmacologic approaches, PRX-100 (Presbyopia Therapies, Coronado, California), employs the pinhole effect with a twist, according to Terry Kim, MD, professor of ophthalmology, Duke University Eye Center, Durham, continued on page 58 by Maxine Lipner EyeWorld Senior Contributing Writer Nonsurgical treatment of presbyopia Pharmaceutical focus June 2017 EW REFRACTIVE 56

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