{'fraction_non_alphanumeric': 0.023367065317387303, 'fraction_numerical': 0.01140754369825207, 'mean_word_length': 5.006629834254143, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 1, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Is it worthwhile to combine penetrating keratoplasty with glaucoma drainage implants?

In the October 2007 issue of Cornea, Ritterband and the Cornea Glaucoma Implant Study (COGIS) group reported on 83 eyes treated with combined penetrating keratoplasty (PK) and implantation of a glaucoma drainage device (GDD), with tube placement in the pars plana. Their graft survival rates are among the best reported for this combination of surgeries, with clear grafts in 93% of the treated eyes at 6 months, 87% at 1 year, and 59% at 2 years. However, no grafts remained clear in the small group of patients at 5-year follow-up. The previous report of Kwon et al of long-term results after PK combined with GDD implantation, with placement of the tube in the anterior chamber, also had no clear grafts at 5 years. Do these studies suggest that grafts and tubes do not mix or that these surgeries should not be combined? The COGIS report is important because it highlights many of the difficulties encountered in a complicated group of patients who have severe corneal and glaucoma problems. One could look at the gradually decreasing graft survival rate each year and decide that treating these eyes is hopeless. However, as the authors point out, they were able to improve vision in many eyes for several years. Without surgery, those patients would have continued to lose vision to glaucoma or deteriorating corneal disease. The key is to carefully evaluate studies, such as this, to figure out how we can improve graft survival in eyes with GDDs. A key question this study raises is: Does GDD tube placement affect PK survival? Most corneal surgeons would agree that a long tube in the anterior chamber could directly damage the cornea and cause chronic inflammation, just as a poorly positioned anterior-chamber lens can. However, is a short, properly positioned tube in the anterior chamber worse for graft survival than one placed in the pars plana? Ritterband et al rightly point out that direct comparison between different studies is difficult because of various patient demographics, surgical techniques, length of follow-up, and definitions of success. The graft survival results of Kwon et al at 5 years with anterior-chamber tubes were similar to those of Ritterband et al with pars plana tubes. Arroyave et al reported better PK survival rates with GDD tubes in the pars plana than with the anterior chamber; however, the patients were not randomized, and different demographics in the treatment groups may have influenced outcomes. If tube placement in the posterior segment truly causes less damage to the PK endothelium, why were no grafts clear at 5 years? What caused the grafts to fail? Interestingly, Ritterband et al reported only an 11% incidence of immunologic graft rejection. Although they did not specify the other reasons for graft failure, they probably included endothelial failure without documented immunologic reactions, ocular surface problems, or undocumented immunologic reactions. Other studies of GDD with PK have reported higher rates of immunologic rejection. We have previously reported that, for initial PKs, the use of preoperative glaucoma medications was the only risk factor that significantly increased the chance of graft failure by all 3 of the primary causes: immunologic graft rejection, endothelial failure without documented immunologic reactions, and ocular surface disease. Although we found that the risk of graft failure was significantly higher when glaucoma was treated with topical medications alone, this study and others suggest that the risk of graft failure is even greater in eyes that require a GDD to control pressure. Clearly, we need better methods of treating glaucoma that do not increase inflammation in the eye or on the ocular surface. One reason that GDDs are thought to increase the risk of graft failure is because the blood–aqueous barrier is breached, and inflammatory cells and debris can reflux into the eye. In 1989, we described suture ligation of tubes in the anterior chamber with subsequent use of an argon laser to open the tube, as needed to control intraocular pressure (IOP). A striking observation was the accumulation of cellular and inflammatory debris in the lumen of the tube above the suture ligature when the tube was totally closed off. This material stayed in the tube until the suture was opened with the laser, several weeks postoperatively. After the tube was opened, the inflammatory debris mixed with the anterior-chamber fluid. Cellular debris also accumulated around the plate and could also have contributed to intraocular inflammation. Some GDD designs attempt to minimize reflux of inflammatory material. For example, the Ahmed implants have a narrow lumen, which limits flow, and it was hoped that this would minimize backflow into the eye from the area of the bleb where the blood–aqueous barrier is breached. Ritterband et al did not find that their 14 eyes with Ahmed implants had better Received for publication July 16, 2007; revision received September 15, 2007; accepted September 19, 2007. From the *Price Vision Group, Indianapolis, IN; and the †Cornea Research Foundation of America, Indianapolis, IN. Drs. Price and Price are consultants for LUX Biosciences. Reprints: Marianne O. Price, 9002 N Meridian Street, Suite 212, Indianapolis, IN 46260 (e-mail: mprice@cornea.org). Copyright 2008 by Lippincott Williams & Wilkins