Cyclophotocoagulation for glaucoma after penetrating keratoplasty

Abstract

We read with great interest the article regarding intractable glaucoma after penetrating keratoplasty reported by Ayyala et al (Ophthalmology 1998;105:1550–6). The authors did not find differences among three procedures (mitomycin C trabeculectomy, glaucoma drainage device implantation, and laser Nd:YAG cyclophotocoagulation) with respect to controlling intraocular pressure (IOP) and graft failure. However, they believe that cyclophotocoagulation is less preferable as the initial treatment of choice because it may be associated with a greater incidence of visual loss and hypotony.1Ayyala R.S. Pieroth L. Vinals A.F. et al.Comparison of mitomycin C trabeculectomy, glaucoma drainage device implantation, and laser neodymium:YAG cyclophotocoagulation in the management of intractable glaucoma after penetrating keratoplasty.Ophthalmology. 1998; 105: 1550-1556Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar We want to emphasize, however, that this thinking would be applicable only to Nd:YAG cyclophotocoagulation. Data about diode laser cyclophotocoagulation are absent. In the contact mode with strong pressure onto the sclera, the Nd:YAG laser should require 2.8 times more energy than the diode laser.2Vogel A. Dlugos C. Nuffer R. Birngruber R. Optical properties of human sclera, and their consequences for transscleral laser applications.Laser Surg Med. 1991; 11: 331-340Crossref PubMed Scopus (146) Google Scholar With less energy delivered, the rate of complications could be reduced. We have prospectively evaluated five eyes of five consecutive patients with uncontrolled glaucoma after penetrating keratoplasty for 18 to 28 months (mean, 22 months) after contact trans-scleral diode laser cyclophototocoagulation (unpublished data). The mean pretreatment IOP was 41.8 ± 8.7 mmHg. At final follow-up, the mean IOP was 13.6 ± 3.7 mmHg (P < 0.05). The mean percentage reduction in IOP was 66.7%. Visual acuity improved in four patients and remained stable in the other eye. No patient showed hypotony, graft failure, or phthisis. Retreatment was necessary in four patients. Ayyala et al retreated 2 of 11 patients.1Ayyala R.S. Pieroth L. Vinals A.F. et al.Comparison of mitomycin C trabeculectomy, glaucoma drainage device implantation, and laser neodymium:YAG cyclophotocoagulation in the management of intractable glaucoma after penetrating keratoplasty.Ophthalmology. 1998; 105: 1550-1556Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar The rate of retreatment for contact Nd:YAG cyclophotocoagulation in refractory glaucoma reported in the literature is higher (range, 27%–54%).3Schuman J.S. Bellows A.R. Shingleton B.J. et al.Contact transscleral Nd:YAG laser cyclophotocoagulation. Midterm results.Ophthalmology. 1992; 99: 1089-1095Abstract Full Text PDF PubMed Scopus (107) Google Scholar, 4Brancato R. Giovanni L. Trabucchi G. Pietroni C. Contact transscleral cyclophotocoagulation with Nd:YAG laser in uncontrolled glaucoma.Ophthalmic Surg. 1989; 20: 547-551PubMed Google Scholar This fact could explain the lesser rate of successful IOP control compared with the other two surgical modalities, although repeated treatment could also induce a greater rate of complications. The low incidence rate of hypotony is an advantage of cyclodiode treatment over other cyclodestructive procedures.5Bloom P.A. Tsai J.C. Sharma K. et al.“Cyclodiode”. Trans-scleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma.Ophthalmology. 1997; 104: 1508-1520Abstract Full Text PDF PubMed Google Scholar Bloom et al5Bloom P.A. Tsai J.C. Sharma K. et al.“Cyclodiode”. Trans-scleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma.Ophthalmology. 1997; 104: 1508-1520Abstract Full Text PDF PubMed Google Scholar did not report any case of hypotony in 173 eyes receiving diode laser cyclophotocoagulation as the primary cycloablation modality. Only one of these 173 eyes developed hypotony after a repeat cyclodiode treatment (0.6%). No patient who previously had glaucoma after penetrating keratoplasty had this complication. They reported that visual acuity decreased in 28% of the patients, but the etiologies more common were neovascular glaucoma and glaucoma after retinal detachment and/or silicone oil surgery. They found graft failure in 2 of 21 patients (9.1%) after laser application.5Bloom P.A. Tsai J.C. Sharma K. et al.“Cyclodiode”. Trans-scleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma.Ophthalmology. 1997; 104: 1508-1520Abstract Full Text PDF PubMed Google Scholar Taking into account these findings and our clinical impression, the risk of hypotony and visual loss associated with diode laser is lower than that previously reported with Nd:YAG laser. At this moment, we cannot get adequate conclusions about the efficacy and safety of cyclodiode in patients with glaucoma after penetrating keratoplasty, but the lesser energy delivered and these preliminary data suggest that diode laser could be a good alternative for these patients. Larger prospective studies are needed to clarify the role of cyclodiode in glaucoma after penetrating keratoplasty. Cyclophotocoagulation for glaucoma after penetrating keratoplasty: Author’s replyOphthalmologyVol. 106Issue 4Preview Full-Text PDF