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New Orleans—Patients with refractory glaucoma may be candidates for transscleral or endoscopic cyclophotocoagulation (CPC) to lower IOP (Figure 1), although there is no direct evidence comparing the two approaches, explained Neeru Gupta, MD, PhD.
The transscleral CPC technique approved by the FDA in 1994 uses a 810-nm continuous-wave diode laser. It has been shown in numerous published studies to lower IOP and allow patients to retain vision in about two-thirds of cases with intermediate follow-up. This approach may require multiple re-treatments, said Dr. Gupta, director of the Glaucoma Unit, St. Michael's Hospital, Department of Ophthalmology and Vision Sciences, University of Toronto, who spoke during the glaucoma subspecialty day at the American Academy of Ophthalmology annual meeting.
"The transscleral approach using a diode laser has been shown prospectively in a randomized trial to be equivalent to the Nd:YAG technique," she noted.
Bloom and colleagues in 1997 published a report in Ophthalmology that showed an overall success rate (IOP <22 mm Hg) was achieved in 66% of 210 eyes at a mean follow-up of 10 months in 195 patients who underwent transscleral CPC with a diode laser for advanced refractory glaucoma. Pediatric patients with this condition have not fared as well with transscleral CPC utilizing a diode laser, with an overall success rate of 50% at 6 months follow-up, according to a 1997 report by Bock et al. in the Journal of Pediatric Ophthalmology and Strabismus.
Only a few retrospective studies have been published concerning endoscopic laser surgery for refractory glaucoma. The largest of these, by Chen and colleagues in 1997 (AJO), reported performing endoscopic laser therapy on 68 eyes. Ninety percent of the eyes (61 eyes) achieved an IOP of <21 mm Hg. "They found a success rate of 94% at 1 year and 84% at 2 years, and 6% (four eyes) had vision loss of 2 or more lines of Snellen acuity," Dr. Gupta noted.
Again, the pediatric population did not do as well with endoscopic CPC, similar to the transscleral CPC results, she said. At 3-year follow-up, Plager and Neely reported in the Journal of the American Association for Pediatric Ophthalmology and Strabismus in 1999 that 50% of 10 eyes (eight patients) that received a single treatment of endoscopic CPC had an IOP of <22 mm Hg with or without glaucoma medications. In 2001, they reported that the success rate had dropped to 34% at 6-year follow-up in 36 eyes of 29 pediatric patients treated with this procedure.
Of interest, endoscopic CPC has been compared with the Ahmed drainage implant in refractory glaucoma in a report by Lima and colleagues and published in the Journal of Glaucoma in 2004. At 24 months, 71% of patients achieved success with the drainage device and 74% with the endoscopic procedure, Dr. Gupta noted.