|In one small study involving the EYEOP1 system, which uses ultrasound to ablate the ciliary body, two different lengths of exposure both lowered IOP significantly. The first group (green line) received three seconds of ultrasound; the second group (red line) received four seconds.|
This is not the first time ultrasound has been tried as a means to lower IOP. In 2000, a Swedish ophthalmologist, Bjorn Svedbergh, MD, created a device designed to use non-focused ultrasound to shake loose particles from the trabecular meshwork; and Jackson Coleman, MD, has used ultrasound to ablate the ciliary body as a means to lower IOP.1
Reducing Aqueous Production
An instrument that has already received the CE mark for treating refractory glaucoma, developed by EyeTechCare in Rillieux-la-Pape, France, uses high-intensity focused ultrasound to trigger hyperthermia in tiny line-segment-shaped focal areas in the ciliary body, causing coagulation that reduces the production of aqueous, resulting in lowered IOP. The device, called EYEOP1, includes a command module for setting parameters and a disposable therapy device that’s placed on the eye following local anesthesia. The therapy device consists of a cone for positioning and fixation and a probe that generates the ultrasound beam. No speculum is necessary, and the procedure can be performed on an outpatient basis in an exam room.
One innovative aspect of this treatment is that the EYEOP1 system treats the entire circumference of the eye in about a minute. This eliminates the need for multiple manual applications, which invite error and limit reproducibility. Furthermore, in contrast to laser cyclodestruction, this treatment has produced no noticeable inflammation or transient increases in pressure in clinical studies, according to the company.
|The EYEOP1 therapy device consists of a cone for positioning and a probe that generates the ultrasound beam.|
EyeTechCare has begun a follow-up study designed to collect data from a larger number of patients at 20 international centers throughout Europe, to confirm the treatment’s efficacy and lack of resulting inflammation. Currently, treatment is indicated only for patients with refractory glaucoma; the company plans to extend the indications once data from a larger number of cases has been published. A spokesman for the company says that results of the new trial should be available early in second quarter 2012; the company plans to bring the technology to market shortly thereafter.
Another ultrasound instrument, designed to reduce IOP by increasing outflow, is under development at Eye Sonix in Long Beach, Calif. The device is the brainchild of longtime cataract surgeon Donald Schwartz, MD.
“Right now, many surgeons believe IOP decreases following cataract surgery because of the increase in the angle,” says Dr. Schwartz. “That’s certainly true with narrow angles. But in the past, when we did intracapsular cataract extraction and extracaps, studies didn’t find that effect.2 Furthermore, two studies—one published3 and one presented at ASCRS in 2009 by Shilpi Pradhan, MD—found that the increase in angle after cataract surgery doesn’t correlate with the decrease in IOP. On the other hand, both studies found a very strong correlation with preoperative IOP.”
Dr. Schwartz’s instrument is designed to increase outflow by creating localized hyperthermia at the trabecular meshwork and in the angle. He’s been developing it since 2006. “The current model of the device is applied to the outside of the eye adjacent to the limbus after a topical anesthetic,” he explains. “Ultrasound is applied circumferentially around the limbus at all 12 clock hours for several seconds. The device produces a temperature at the target area high enough to trigger a cytokine cascade, but low enough to avoid causing pain or cell necrosis.”
Dr. Schwartz says his studies (not yet published) have shown that the device causes a decrease in IOP comparable to selective laser trabeculoplasty. “The procedure is repeatable, and the majority of subjects treated have maintained lowered pressure for at least a year,” he says. “It also causes a pressure decrease in the fellow eye, as has been observed in SLT.”
Dr. Schwartz notes that it’s widely accepted that SLT works by triggering a cytokine cascade, leading to the production of enzymes and macrophage induction. “The enzymes break down trabecular meshwork debris and the macrophages clear it away, thus increasing outflow,” he says. “At the same time, a study done by Joel Schuman, MD, has demonstrated that cataract surgery using ultrasound leads to certain very specific inflammatory cytokines being present after surgery.4 The similarities between my results and SLT, and the knowledge that phacoemulsification can trigger cytokines, leads me to believe that a cytokine cascade is the mechanism of action that explains our results.”
Could this treatment be affecting the ciliary body as well, mimicking the effect produced by the French device? Dr. Schwartz agrees that some of the focused ultrasound could be reaching the ciliary body. However, he notes that the energy level used in his treatment is far below the level that would result in tissue ablation. “A lack of effect on the ciliary body in treated rabbit eyes was confirmed by histopathology,” he adds. “And the fact that this treatment causes a drop in IOP in the fellow eye also supports the idea that the mechanism is similar to SLT rather than ciliary ablation.”
Dr. Schwartz notes that using the Eye Sonix device has many of the same advantages as SLT. “However, this procedure should be a little easier to perform than SLT,” he says. “The device will be battery-powered and about the size of a laptop computer. Because it doesn’t require a slit lamp, microscope or contact lens to deliver the treatment, it should be possible to treat glaucoma in parts of the world where treatment has been nearly impossible up to now.” Dr. Schwartz is currently doing the work required to obtain a CE mark.
1. Valtor F, Kopel J, Haut J. Treatment of glaucoma with high intensity focused ultrasound. Internat Ophth 1989;13:167-170.
2. Radius RL, Schultz K, Sobocinski K, Schultz RO, Easom H. Pseudophakia and intraocular pressure. Am J Ophthalmol 1984;97:738–42.
3. Doganay S, Bozgul Firat P, Emre S, Yologlu S. Evaluation of anterior segment parameter changes using the Pentacam after un-
eventful phacoemulsification. Acta Ophthalmol 2010;88:5:601-6.
4. Wang N, Chintala SK, Fini ME, Schuman JS. Ultrasound activates the TM ELAM-1/IL-1/NF-kappaB response: A poten-tial mechanism for intraocular pressure reduction after phaco-emulsification. Invest Ophthalmol Vis Sci 2003;44:5:1977-81.