- Email: [email protected]
Long-term Complications Associated with Glaucoma Drainage Devices and Boston Keratoprosthesis
We thank the authors for bringing out the effect of data clustering that can happen with the Mann–Whitney U test. Rosner and associates used extension of the signed-rank test for clustered data. They proposed a corrected variance formula of the Wilcoxon signed-rank test.5 Kitaya and associates used the Mann–Whitney U test to compare choroidal blood flow in eyes with central serous chorioretinopathy and their fellow eyes.3 Choroidal blood flow measurements were obtained in 22 eyes of 11 patients with central serous chorioretinopathy and were compared with fellow eyes.3 Contreras and associates reported the comparison of unaffected and affected eyes with nonarteritic anterior ischemic optic neuropathy using the Mann–Whitney U test.4 They compared the optic nerve head changes, namely, the disc area and cup-to-disc ratio, at various time points, such as the acute phase, 3 months, and 6 months,4 in affected eyes and fellow eyes. We admit that the clustering effect can occur in data comparisons like this involving fellow eye comparisons in nonparametric tests. However, both the Wilcoxon and Mann–Whitney U tests can be used with debatable adjustments for clustered data in ophthalmology. DHIVYA ASHOK KUMAR AMAR AGARWAL GAURAV PRAKASH SOUNDARI SIVANGANAM SOOSAN JACOB ATHIYA AGARWAL
Chennai, India
CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article1 for any disclosures of the authors.
REFERENCES
1. Kumar DA, Agarwal A, Prakash G, et al. Viscocannulaassisted reinversion of implantable collamer lens: comparison of postoperative outcomes with the fellow eyes. Am J Ophthalmol 2012;153(1):62– 67. 2. Rosner B, Glynn RJ, Lee ML. The Wilcoxon signed rank test for paired comparisons of clustered data. Biometrics 2006; 62(1):185–192. 3. Kitaya N, Nagaoka T, Hikichi T, et al. Features of abnormal choroidal circulation in central serous chorioretinopathy. Br J Ophthalmol 2003;87(6):709 –712. 4. Contreras I, Rebolleda G, Noval S, Muñoz-Negrete FJ. Optic disc evaluation by optical coherence tomography in nonarteritic anterior ischemic optic neuropathy. Invest Ophthalmol Vis Sci 2007;48(9):4087– 4092. 5. Rosner B, Glynn RJ, Lee ML. Extension of the rank sum test for clustered data: two-group comparisons with group membership defined at the subunit level. Biometrics 2006;62(4): 1251–1259.
VOL. 154, NO. 1
Long-term Complications Associated with Glaucoma Drainage Devices and Boston Keratoprosthesis EDITOR: WE READ WITH INTEREST THE ARTICLE BY LI AND ASSOCI-
ates that comments on the incidence of tube erosion in eyes with a Boston keratoprosthesis (KPro) and a glaucoma drainage device (GDD), covered by a soft contact lens. They found 10 conjunctival erosions over the tube among 25 eyes with a GDD. In 2 of these eyes, endophthalmitis developed, and among all 10 eyes, 6 devices were removed. The authors ascribed the erosions to rubbing by the edge of the soft lens.1 Chew and associates also reported 1 case of tube erosion from among 31 eyes.2 Moussally and HarissiDagher subsequently described 8 cases with a KPro plus a GDD, followed up for a mean of 24 months, without any tube erosion.3 We would like to comment on our experience at the Massachusetts Eye and Ear Infirmary with tube erosion and endophthalmitis (presented as a poster at the American Glaucoma Society Meeting, March 4 –7, 2011, Dana Point, California). We reviewed approximately 130 charts of patients with both a KPro and a GDD performed in the last 5 years. Nineteen erosions were found: 7 (37%) of 19 resolved without surgical intervention on change of contact lens. Five (26%) of 19 underwent tube revision. Four (21%) of 19 underwent tube explantation. Three (16%) of 19 have stable erosions to date with no leaks or hypotony. In none of these patients did endophthalmitis developed. Daily prophylactic drops with at least some efficacy against both gram-positive and gram-negative bacteria were used, for example, polymyxin B/trimethoprim or vancomycin (14 mg/mL) plus a fourth-generation fluoroquinolone. We agree with Li and associates that the mechanical trauma from the edge of the soft contact lens (usually a Kontur lens [Konkur Kontact Lens Co Inc, Hercules, California, USA] with a 16-mm diameter) is the main cause of tube erosions.1 In support of this theory, changing the diameter of the contact lens resolved the erosion in one third of our cases. Moussally and Harissi-Dagher raised the question whether vancomycin toxicity to the conjunctiva could be a factor—Li and associates used a high concentration (50 mg/mL vs the more commonly chosen concentration of 14 mg/mL) twice daily for prophylaxis.2 However, this possibility still does not explain the resolution of the erosion with change in the contact lens diameter with continuation of vancomycin. We do not advocate the cessation of vancomycin use in high-risk patients because its use has for us dramatically reduced the rate of bacterial endophthalmitis from 12% in the decade 1990 through 1999 to 1% in the following decade, in similar patient populations (unpublished). Given that endophthalmitis did not develop in any of our patients with an exposed tube, we propose that tube
CORRESPONDENCE
207
erosions in patients with a KPro may not need to be managed very aggressively with surgical interventions unless clear hypotony or discomfort exists. Theoretically, with prophylactic antibiotics, an exposed tube through the conjunctiva should provide no more risk of endophthalmitis than the presence of a KPro, which is similarly exposed above the tissue surface. In addition, tube revision may not be an entirely harmless procedure—1 of the 2 endophthalmitis cases reported by Li and associates occurred after repair of the tube erosion. Therefore, with the continued prophylactic use of a low-dose, broad-spectrum combination of antibiotics and changing the contact lens diameter, these patients may be given a chance to avoid further surgery with minimal risk of endophthalmitis and considerable likelihood of spontaneous recovery.
of their patients with both a Boston keratoprosthesis and a GDD over the past 5 years (n ⫽ 130). This is not an insignificant complication rate in these patients. Before the publication of our findings at the University of California, Davis, the literature has been quite sparse regarding this particular complication of keratoprosthesis surgery, with only one other report of conjunctival erosions over tube shunts.2 Given our findings and this subsequent report by Patel and associates, we speculate that this is an underreported complication of Boston keratoprosthesis surgery. Their suggestion of changing the diameter of the contact lens in cases where mechanical trauma from the contact lens may be contributing to the GDD erosion is a valuable one. Their resolution rate of 37% with this simple adjustment is encouraging. Cortina and associates also suggested placing a more posterior pars plana tube with a lamellar corneal patch graft to decrease and eliminate friction between the contact lens edge and the tube and to prevent such erosions from occurring entirely.3 One reservation we have regarding the suggestion by Patel and associates to observe stable erosions in patients without leaks, hypotony, or discomfort is the continued concern for potential ocular infections. We certainly agree that daily prophylaxis with a combination of topical vancomycin and another broad-spectrum commercially available topical antibiotic decreases the risk of bacterial endophthalmitis. However, it does not address the increasing concern of potential fungal infections in these patients. Fungal infections have increased since the use of broad-spectrum antibiotic prophylaxis, and therapeutic contact lenses have been recommended.4,5 Although low, the risk of a devastating complication associated with fungal colonization of an eroded GDD is not negligible. Ultimately, the key for management of these patients is a multidisciplinary approach to their care. Close coordination between the corneal surgeon and the glaucoma specialist involved in the follow-up of these patients will determine whether observation or surgical intervention is most appropriate in each individual case.
SHUCHI PATEL
Maywood, Illinois HANA TAKUSAGAWA LUCY SHEN CLAES DOHLMAN CYNTHIA GROSSKREUTZ
Boston, Massachusetts CONFLICT OF INTEREST DISCLOSURES: ALL AUTHORS have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and the following were reported. Dr Shen is a consultant to Allergan. Dr Dohlman’s institution receives grants for the KPro.
REFERENCES
1. Li JY, Greiner MA, Brandt MC, Lim MC, Mannis MJ. Long-term complications associated with glaucoma drainage devices and Boston keratoprosthesis. Am J Ophthalmol 2011; 152(2):209 –218. 2. Chew HF, Ayers BD, Hammersmith KM et al. Boston keratoprosthesis outcomes and complications. Cornea 2009;28(9): 989 –996. 3. Moussally K, Harissi-Dagher M. Long-term complications associated with glaucoma drainage devices and Boston keratoprosthesis [letter]. Am J Ophthalmol 2011;152(5):883– 884; author reply 884 – 885.
JENNIFER Y. LI JAMES D. BRANDT MICHELE C. LIM MARK J. MANNIS
Sacramento, California
REPLY
MARK A. GREINER
Portland, Oregon
WE WERE EXTREMELY INTERESTED TO READ THE COM-
ments from Patel and associates in response to our article, “Long-term Complications Associated with Glaucoma Drainage Devices and Boston Keratoprosthesis.”1 We appreciate the insight they provide regarding their experiences at the Massachusetts Eye and Ear Infirmary with glaucoma drainage device (GDD) erosions and Boston keratoprosthesis surgery. It is of particular interest that they observed 19 cases of conjunctival erosion over GDDs. This accounts for 14.6% 208
AMERICAN JOURNAL
CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article1 for any disclosures of the authors.
REFERENCES
1. Li JY, Greiner MA, Brandt MC, Lim MC, Mannis MJ. Long-term complications associated with glaucoma drainage OF
OPHTHALMOLOGY
JULY
2012
Chennai, India
CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article1 for any disclosures of the authors.
REFERENCES
1. Kumar DA, Agarwal A, Prakash G, et al. Viscocannulaassisted reinversion of implantable collamer lens: comparison of postoperative outcomes with the fellow eyes. Am J Ophthalmol 2012;153(1):62– 67. 2. Rosner B, Glynn RJ, Lee ML. The Wilcoxon signed rank test for paired comparisons of clustered data. Biometrics 2006; 62(1):185–192. 3. Kitaya N, Nagaoka T, Hikichi T, et al. Features of abnormal choroidal circulation in central serous chorioretinopathy. Br J Ophthalmol 2003;87(6):709 –712. 4. Contreras I, Rebolleda G, Noval S, Muñoz-Negrete FJ. Optic disc evaluation by optical coherence tomography in nonarteritic anterior ischemic optic neuropathy. Invest Ophthalmol Vis Sci 2007;48(9):4087– 4092. 5. Rosner B, Glynn RJ, Lee ML. Extension of the rank sum test for clustered data: two-group comparisons with group membership defined at the subunit level. Biometrics 2006;62(4): 1251–1259.
VOL. 154, NO. 1
Long-term Complications Associated with Glaucoma Drainage Devices and Boston Keratoprosthesis EDITOR: WE READ WITH INTEREST THE ARTICLE BY LI AND ASSOCI-
ates that comments on the incidence of tube erosion in eyes with a Boston keratoprosthesis (KPro) and a glaucoma drainage device (GDD), covered by a soft contact lens. They found 10 conjunctival erosions over the tube among 25 eyes with a GDD. In 2 of these eyes, endophthalmitis developed, and among all 10 eyes, 6 devices were removed. The authors ascribed the erosions to rubbing by the edge of the soft lens.1 Chew and associates also reported 1 case of tube erosion from among 31 eyes.2 Moussally and HarissiDagher subsequently described 8 cases with a KPro plus a GDD, followed up for a mean of 24 months, without any tube erosion.3 We would like to comment on our experience at the Massachusetts Eye and Ear Infirmary with tube erosion and endophthalmitis (presented as a poster at the American Glaucoma Society Meeting, March 4 –7, 2011, Dana Point, California). We reviewed approximately 130 charts of patients with both a KPro and a GDD performed in the last 5 years. Nineteen erosions were found: 7 (37%) of 19 resolved without surgical intervention on change of contact lens. Five (26%) of 19 underwent tube revision. Four (21%) of 19 underwent tube explantation. Three (16%) of 19 have stable erosions to date with no leaks or hypotony. In none of these patients did endophthalmitis developed. Daily prophylactic drops with at least some efficacy against both gram-positive and gram-negative bacteria were used, for example, polymyxin B/trimethoprim or vancomycin (14 mg/mL) plus a fourth-generation fluoroquinolone. We agree with Li and associates that the mechanical trauma from the edge of the soft contact lens (usually a Kontur lens [Konkur Kontact Lens Co Inc, Hercules, California, USA] with a 16-mm diameter) is the main cause of tube erosions.1 In support of this theory, changing the diameter of the contact lens resolved the erosion in one third of our cases. Moussally and Harissi-Dagher raised the question whether vancomycin toxicity to the conjunctiva could be a factor—Li and associates used a high concentration (50 mg/mL vs the more commonly chosen concentration of 14 mg/mL) twice daily for prophylaxis.2 However, this possibility still does not explain the resolution of the erosion with change in the contact lens diameter with continuation of vancomycin. We do not advocate the cessation of vancomycin use in high-risk patients because its use has for us dramatically reduced the rate of bacterial endophthalmitis from 12% in the decade 1990 through 1999 to 1% in the following decade, in similar patient populations (unpublished). Given that endophthalmitis did not develop in any of our patients with an exposed tube, we propose that tube
CORRESPONDENCE
207
erosions in patients with a KPro may not need to be managed very aggressively with surgical interventions unless clear hypotony or discomfort exists. Theoretically, with prophylactic antibiotics, an exposed tube through the conjunctiva should provide no more risk of endophthalmitis than the presence of a KPro, which is similarly exposed above the tissue surface. In addition, tube revision may not be an entirely harmless procedure—1 of the 2 endophthalmitis cases reported by Li and associates occurred after repair of the tube erosion. Therefore, with the continued prophylactic use of a low-dose, broad-spectrum combination of antibiotics and changing the contact lens diameter, these patients may be given a chance to avoid further surgery with minimal risk of endophthalmitis and considerable likelihood of spontaneous recovery.
of their patients with both a Boston keratoprosthesis and a GDD over the past 5 years (n ⫽ 130). This is not an insignificant complication rate in these patients. Before the publication of our findings at the University of California, Davis, the literature has been quite sparse regarding this particular complication of keratoprosthesis surgery, with only one other report of conjunctival erosions over tube shunts.2 Given our findings and this subsequent report by Patel and associates, we speculate that this is an underreported complication of Boston keratoprosthesis surgery. Their suggestion of changing the diameter of the contact lens in cases where mechanical trauma from the contact lens may be contributing to the GDD erosion is a valuable one. Their resolution rate of 37% with this simple adjustment is encouraging. Cortina and associates also suggested placing a more posterior pars plana tube with a lamellar corneal patch graft to decrease and eliminate friction between the contact lens edge and the tube and to prevent such erosions from occurring entirely.3 One reservation we have regarding the suggestion by Patel and associates to observe stable erosions in patients without leaks, hypotony, or discomfort is the continued concern for potential ocular infections. We certainly agree that daily prophylaxis with a combination of topical vancomycin and another broad-spectrum commercially available topical antibiotic decreases the risk of bacterial endophthalmitis. However, it does not address the increasing concern of potential fungal infections in these patients. Fungal infections have increased since the use of broad-spectrum antibiotic prophylaxis, and therapeutic contact lenses have been recommended.4,5 Although low, the risk of a devastating complication associated with fungal colonization of an eroded GDD is not negligible. Ultimately, the key for management of these patients is a multidisciplinary approach to their care. Close coordination between the corneal surgeon and the glaucoma specialist involved in the follow-up of these patients will determine whether observation or surgical intervention is most appropriate in each individual case.
SHUCHI PATEL
Maywood, Illinois HANA TAKUSAGAWA LUCY SHEN CLAES DOHLMAN CYNTHIA GROSSKREUTZ
Boston, Massachusetts CONFLICT OF INTEREST DISCLOSURES: ALL AUTHORS have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and the following were reported. Dr Shen is a consultant to Allergan. Dr Dohlman’s institution receives grants for the KPro.
REFERENCES
1. Li JY, Greiner MA, Brandt MC, Lim MC, Mannis MJ. Long-term complications associated with glaucoma drainage devices and Boston keratoprosthesis. Am J Ophthalmol 2011; 152(2):209 –218. 2. Chew HF, Ayers BD, Hammersmith KM et al. Boston keratoprosthesis outcomes and complications. Cornea 2009;28(9): 989 –996. 3. Moussally K, Harissi-Dagher M. Long-term complications associated with glaucoma drainage devices and Boston keratoprosthesis [letter]. Am J Ophthalmol 2011;152(5):883– 884; author reply 884 – 885.
JENNIFER Y. LI JAMES D. BRANDT MICHELE C. LIM MARK J. MANNIS
Sacramento, California
REPLY
MARK A. GREINER
Portland, Oregon
WE WERE EXTREMELY INTERESTED TO READ THE COM-
ments from Patel and associates in response to our article, “Long-term Complications Associated with Glaucoma Drainage Devices and Boston Keratoprosthesis.”1 We appreciate the insight they provide regarding their experiences at the Massachusetts Eye and Ear Infirmary with glaucoma drainage device (GDD) erosions and Boston keratoprosthesis surgery. It is of particular interest that they observed 19 cases of conjunctival erosion over GDDs. This accounts for 14.6% 208
AMERICAN JOURNAL
CONFLICT OF INTEREST DISCLOSURES: SEE THE ORIGINAL article1 for any disclosures of the authors.
REFERENCES
1. Li JY, Greiner MA, Brandt MC, Lim MC, Mannis MJ. Long-term complications associated with glaucoma drainage OF
OPHTHALMOLOGY
JULY
2012