Ahmed Glaucoma Valve and Single-Plate Molteno Implants in Treatment of Refractory Glaucoma: A Comparative Study

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Ahmed Glaucoma Valve and Single-Plate Molteno Implants in Treatment of Refractory Glaucoma: A Comparative Study
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  Ahmed Glaucoma Valve and Single-Plate MoltenoImplants in Treatment of Refractory Glaucoma: AComparative Study NADER NASSIRI, GHAZAL KAMALI, MOHAMMAD RAHNAVARDI, BABAK MOHAMMADI, SAMAN NASSIRI,LALEH RAHMANI, AND NARIMAN NASSIRI ●  PURPOSE:  Toreport2-yearfollow-updataafterAhmedvalve implantation (New World Medical, Inc) and Mol-teno single-plate implantation surgical treatment of re-fractory glaucoma. ●  DESIGN:  Prospective, randomized, comparative study. ●  METHODS:  Patients with refractory glaucoma, definedas uncontrolled intraocular pressure (IOP) of more than21 mm Hg despite maximal antiglaucoma medication,previously failed nonseton surgical treatment, or a com-binationthereofwereincluded.Ninety-twopatientswereallocated randomly to each of the study groups andunderwent implantation of either the Ahmed valve im-plant (model FP7; 184 mm 2 surface area) or Moltenosingle-plate implant (134 mm 2 surface area) and werefollowed up for 24 months. Main outcome measures wereIOP and surgical success rate. Other outcome measureswere changes in visual acuity, number of ant-glaucomamedications, mean deviation of visual field, and rate ofintraoperative and postoperative complications. ●  RESULTS:  Those who successfully completed the trial(28 in the Molteno group and 29 in the Ahmed group)achieved significantly less IOP and fewer glaucoma med-ications, but worse visual acuity 24 months after surgery.The Molteno group, compared with the Ahmed group,achieved significantly lower IOPs after the early postop-erative period until the end of the study. Both groupsreasonably maintained visual field during the follow-up.The rate of surgical failure was comparable in bothgroups. Median survival time was 24 months for bothgroups. There were no devastating intraoperative orpostoperative complications in either group. ●  CONCLUSIONS:  Both Ahmed and Molteno implantssuccessfully preserved visual field, although IOP controlwas more pronounced in the Molteno implant group.(Am J Ophthalmol 2010;149:893–902. © 2010 byElsevier Inc. All rights reserved.) H ISTORICALLY, GLAUCOMA DRAINAGE IMPLANTS have been reserved for cases of refractory glau-coma deemed at high risk of failure (e.g., eyeswith a previous history of failed trabeculectomy 1,2 and withneovascular and uveitic glaucoma) with standard filtrationsurgery. Despite the high-risk profile of these patients,moderately good levels of success with various types of glaucoma drainage implants have been observed. Conse-quently, the use of these implants has increased in recentyears, and they have become the preferred surgical proce-dure for complex cases. 3,4 For more than 2 decades, various types of glaucomadrainage implants have been developed. These implantsmay be subdivided into valved and nonvalved designs.Those with a nonvalved structure act as an open tube,which may result in immediate postoperative hypotony 5,6 and its attendant complications (e.g., flat anterior cham-ber, suprachoroidal effusion, and suprachoroidal hemor-rhage). Hypotony during the immediate postoperativeperiod is less common with valved drainages, although itmay still occur. 7–10 We investigated the success of theAhmed valve implant (New World Medical, Inc, RanchoCucamonga, California, USA) and the Molteno single-plate implant (Molteno Ophthalmic Limited, Dunedin, New Zealand) in treating eyes with refractory glaucomaduring a follow-up period of 24 months. METHODS ●  STUDY SUBJECTS:  A prospective, randomized trial wasperformed from January 2003 through August 2005 at 3medical centers, namely, Imam Hossein Medical Center, Negah Eye Hospital, and Vanak Eye Surgery Center, all inTehran, Iran. The eligibility criteria were refractory glau-coma, defined as uncontrolled intraocular pressure (IOP)despite maximal antiglaucoma medication, previously failednonseton surgical treatment, or a combination thereof. Theexclusion criteria included age younger than 40 years, a visualacuity of no light perception, lens opacity, elevated IOPassociated with silicone oil, previous glaucoma drainagedevice implantation in the same eye, previous cyclodestruc-tive treatment, increased risk of endophthalmitis (e.g., activeadnexal and ocular surface infection, immunosuppression, or See Accompanying Editorial on page 875.Accepted for publication Jan 14, 2010.From the Department of Ophthalmology, Imam Hossein MedicalCenter, Shaheed Beheshti University of Medical Sciences, Tehran, Iran(Nad.N., G.K.); and Vanak Eye Surgery Center, Tehran, Iran (M.R.,B.M., S.N., L.R., Nar.N.).Inquiries to Nariman Nassiri, Vanak Eye Surgery Center, No. 41,Haghani Highway, Vanak, Tehran, Iran; e-mail: drnassirin@sbmu.ac.ir ©  2010 BY  E LSEVIER  I NC . A LL RIGHTS RESERVED . 0002-9394/$36.00  893 doi:10.1016/j.ajo.2010.01.025  immunodeficiency, including the use of systemic steroids),posterior segment disorders, or pre-existing ocular comorbidi-ties (e.g., pterygium, phacodonesis, corneal opacity, or cor-neal endothelial dystrophies). Only 1 eye per patient wasincluded in this trial.An estimation of sample size was performed considering astudy power of at least 0.8 with an  error of 0.05 aiming todetect a difference of 1 mm Hg in mean IOP in thepostoperative month 24 between the 2 groups. Mean IOP inthepostoperativemonth24wasestimatedtobe15mmHginthe Ahmed group based on the results of the previousstudies. 11,12 Based on this estimation, a total of 64 studysubjects was deemed adequate, and considering a total of 30%assumed dropout and failure rate during the follow-up, re-cruitment of at least 92 study subjects was targeted.Of 101 eligible patients, 92 (91.0%) agreed to partici-pate. Study subjects were assigned randomly to either theAhmed or Molteno groups. Randomization was performedusing a random permuted block design with a block size of 2, stratified for age, sex, and hosting medical center. Neither patients nor investigators were masked to studygroups. Figure 1 shows a flow chart of the trial. Operationswere all performed by the same senior right-handed sur-geon (Nad.N.). To reduce the risk of potentially perma-nent visual loss, all patients underwent surgery within 4weeks of enrolling in the trial. Before operation, theexclusion criteria again were reviewed by the surgeon. ●  PREOPERATIVE AND POSTOPERATIVE ASSESSMENTS: Presurgical assessments included slit-lamp biomicroscopicexamination, funduscopy, Snellen visual acuity (VA), base-line IOP, number of antiglaucoma medications, and Hum-phrey perimetry results. Follow-up visits were scheduled atday 1, week 1, and months 1, 3, 6, 9, 12, 18, and 24, and moreoften when necessary. Postoperative evaluations includedassessment of visual acuity, IOP (in millimeters of mercury),number of antiglaucoma medications, lens opacity, and post-operative complications. Humphrey perimetry was performedat postoperative months 3 and thereafter. A formal motilityevaluationwasperformedinallpatientsatbaselineandatthe1-year and 2-year follow-up visits, as well as during any visitsafter 3 months if the patient reported diplopia.The best-corrected visual acuity was measured using aSnellen chart (CP-690; Nidek Co, Ltd, Gamagori Aichi, Japan) calibrated for a 20-foot (approximately 6 m) dis-tance by the line assignment method within the monthbefore the surgery; the figures were converted to logarithmof the minimal angle of resolution notation by the standardconversion table. IOP was measured using a Goldmanapplanation tonometer (AT-900; Haag-Streit AG, Koniz,Switzerland) mounted on a slit lamp; if required, gonios-copy (Haag-Streit AG) also was performed. The preoper-ative IOP for each eye was considered as the last measurebefore operation.24–2 threshold visual field assessment was performed withthe Humphrey Field Analyzer (Allergan-Humphrey Instru-ments, San Leandro, California, USA). The mean devia-tion—a visual field index provided by Statpac-2 (Allergan-HumphreyInstruments) 13 anddeterminedfromacomparisonwith an age-matched normal population—was available as aglobal assessment of visual field damage. We considered thephenomenon of learning effect in our analysis of meandeviation; this is a phenomenon whereby the baseline visualfield is worse than in subsequent tests, 14,15 so using baselinetests may result in a false-positive defect being compared withactual glaucomatous progression or the development of acataract, and not stable fields. To avoid this, we included onlyresults where consecutive field tests did not show an improve-mentof2dBormoreinthemeandeviationoverthebaselinereading.  FIGURE 1. Trial flow chart, the Ahmed valve and Moltenoimplant groups. A    analyzed; CS    complete success; F   intervention failure; L    lost to follow-up; QS    qualifiedsuccess. A MERICAN  J OURNAL OF  O PHTHALMOLOGY 894  J UNE 2010  ●  OUTCOME MEASURES:  IOP (primary outcome mea-sure), number of antiglaucoma medications, visual acuity,visual field, and surgical failure were considered as mea-sures assessing efficacy; intraoperative and postoperativecomplications were considered as measures assessing safety.Surgical failure was defined as persistent IOP of more than21 mm Hg on maximally tolerated medications or IOP lessthan 6 mm Hg on 2 consecutive visits, phthisis bulbi,reduction of vision to no light perception, removal of theshunt implant, reoperation for glaucoma, or any devastat-ing intraoperative or postoperative complication. 11,16 Re-operation was defined as additional glaucoma surgeryrequiring a return to the operating room, such as place-ment of a tube shunt. Interventions performed at the slitlamp, such as needling procedures, were not consideredreoperations. Surgical revision of the glaucoma shuntimplants for other postoperative reasons (e.g., tube repo-sitioning or repair of conjunctival wound dehiscence) wererecorded, but were not considered surgical failures. Devas-tating complications included suprachoroidal hemorrhagethat threatened visual fixation, was likely to develop akissing appearance, or both; malignant glaucoma; endoph-thalmitis; retinal detachment; chronic hypotony; or serouschoroidal effusions necessitating surgical drainage or thathad a kissing appearance.Treatment success was subdivided into complete andqualified. A complete success was defined as IOP between6 and 21 mm Hg without any antiglaucoma medication,and qualified success was defined as IOP between 6 and 21mm Hg with 1 medication or more. Hypotony was definedas an IOP of less than 6 mm Hg on 2 consecutivevisits; 10,12,16 a hypertensive phase was defined as an IOP of more than 21 mm Hg during the first 3 postoperativemonths (with or without medications) after a reduction inIOP to less than 22 mm Hg during the first postoperativeweek and not caused by tube obstruction, retraction, orvalve malfunction. 17 Resolution of this phase was IOP of less than 22 mm Hg along with a reduction of the IOP by3 mm Hg or more with the same or fewer number of medications, or reduction of at least 1 medication with achange in of IOP less than 3 mm Hg. 17 ●  PROCEDURE:  The tube shunts used were either thevalved 184-mm 2 surface area Ahmed Glaucoma Valve(AGV Model FP7) or the 134-mm 2 surface area single-plateMolteno implant. Before the trial, the surgeon made atransition from the polypropylene (model S2) to the silicone(model FP7) Ahmed valve. Recent studies have reportedsignificantly lower failure rates with silicone valves. 18–21 General anesthesia was given in most cases; in some cases, aperibulbar block consisting of lidocaine 2% (Xylocaine;AstraZeneca, Cheshire, United Kingdom) with hyaluron-idase (Hyalase; Wockhardt Ltd, Wrexham, United King-dom) was used. Immediately before surgery in the operatingroom, povidone–iodine 5% was applied to the skin of theeyelids of the operative eye, nose, and forehead. The opera-tive eye was draped in the usual manner for ophthalmicsurgery.Inbothtypesofshunts,aclearcornealtractionsuturewas placed with silk 7-0, and the fornix-based conjunctivalflap and Tenon capsule were fashioned supratemporally. Toprime the valve, the tube of the shunt was irrigated with abalanced saline solution (BSS; Alcon, Fort Worth, Texas, TABLE 1.  Demographic and Baseline Characteristics ofStudy Subjects from the Ahmed Valve Implant andMolteno Single-Plate Implant Groups Characteristics Ahmed ValveImplant(n  46)MoltenoSingle-PlateImplant(n  46) P  Value Demographic characteristicsMean age (SEM), yrs 59.4 (1.51) 63.3 (1.62) .08Male/female, n 25/21 22/24 .67Background conditions, n(%)Diabetes mellitus 11 (23.9) 11 (23.9) 1.00Hypertension 13 (28.3) 13 (28.3) 1.00Family history ofglaucoma 11 (23.9) 10 (21.7) 1.00Bilateral glaucoma 12 (26.1) 14 (30.4) .82Previous glaucomatreatments, n (%)Penetrating iridectomy 8 (17.4) 9 (19.6) 1.00Trabeculectomy 17 (37.0) 18 (39.1) 1.00No. of trabeculectomyprocedures .981 1 (2.2) 1 (2.2)2 14 (30.4) 14 (30.4)3 2 (4.3) 3 (6.5)Enrolled eye baselinefeaturesSide, right/left, n 24/22 20/26 .53Lens group, n (%) .69Phakic 31 (67.4) 33 (71.7) Aphakic 6 (13.0) 7 (15.2)Pseudophakic 9 (19.6) 6 (13.0)Subtypes of glaucoma, n(%) .82Failed filtration 17 (37.0) 19 (41.3)Pseudoaphakia 9 (19.6) 6 (13.0)Neovascular 9 (19.6) 12 (26.1) Aphakia 6 (13.0) 6 (13.0)Uveitic 5 (10.9) 3 (6.5)Mean IOP (SEM), mm Hg 32.11 (1.32) 32.41 (1.27) .87Mean BCVA (SEM), logMARunits 0.64 (0.09) 0.61 (0.09) .86 Visual field mean deviation(SEM), dB –18.57 (0.82) –19.11 (0.79) .64Mean no. of glaucomamedications (SEM) 2.7 (0.08) 2.7 (0.09) .72BCVA     best-corrected visual acuity; dB    decibels; IOP   intraocular pressure; logMAR    logarithm of the minimal angleof resolution; SEM  standard error of mean. A HMED  V ALVE VS  M OLTENO  I MPLANT V OL .  149 , N O .  6  895  USA). The plate was secured 8 to 9 mm posterior to thesurgical limbus with interrupted 7-0 nylon sutures usingtapered cutting needles.In the Molteno implant group, the anterior chamberdrainage tube was occluded by tying a 7-0 Vicryl suture(Ethicon, Norderstedt, Germany) around its exterior, whereit joined the plate of the implant, to restrict the flow throughthe device temporarily until encapsulation of the plate oc-curred. Fenestrations were placed anterior to the suture usinga 28-gauge needle to allow leakage of the aqueous, providinginitial IOP control. Next, in both groups, the tube wastrimmed to extend approximately 2 to 3 mm beyond thesurgical limbus with the bevel facing up; it then was enteredintotheanteriorchamberbya23-gaugeneedleparalleltotheiris plane. If a peripheral iridectomy was present from aprevious surgery, the needle tract was placed slightly to oneside of the iridectomy. Sodium hyaluronate (Healon, 10mg/mL; Advanced Medical Optics, Santa Ana, California,USA) was injected to prevent sudden collapse of theanterior chamber. The tube was inserted with smoothforceps through the needle tract, ensuring that no iris orcorneal touch occurred. In patients with aphakic andpseudophakic glaucoma who had vitreous in the anteriorchamber, an anterior vitrectomy was performed before theplacement of the tube. The tube then was anchored to thesclera using a 10-0 nylon suture and was covered with arectangular piece of donor scleral patch graft. The con-junctiva was closed using 10-0 interrupted nylon sutures. Aclear cornea paracentesis then was created to remove theHealon as much as was possible, and the anterior chamberthen was reformed with BSS. At the end of surgery,subconjunctival injections of antibiotics and corticoste-roids were administered away from the surgical site. Noadjunctive antimetabolite was used in any of the cases.Postoperative management consisted of combination top-ical antibiotic and steroid eye drops, which were taperedover the course of 6 to 8 weeks. Antiglaucoma medicationswere removed or added as needed, depending on the IOPand clinical status of the operated eye. ●  STATISTICAL ANALYSIS:  Preoperative and postopera-tive measures were compared within and between studygroups. Quantitative variables were compared using non-parametric tests, that is, the Mann–Whitney  U  test orWilcoxon signed-rank test, whichever appropriate. The  FIGURE 2. Graph showing the mean preoperative and postop-erative intraocular pressures in the Ahmed valve and Moltenoimplant groups. * P  <  0.001, ** P    0.001, *** P  <  0.01,Mann–Whitney  U   test comparisons of the figures at thedifferent time points between 2 groups. TABLE 2.  Preoperative and Postoperative Month 24 Figures in Those Study Subjects from the Ahmed Valve Implant andMolteno Single-Plate Implant Groups Who Successfully Completed the Trial  Ahmed Valve Implant (n  29) Molteno Single-Plate Implant (n  28)Preoperative Month 24  P  Value  a Preoperative Month 24  P  Value  a Mean IOP (SEM), mm Hg  b 30.81 (1.67) 17.00 (0.23)   0.001 33.06 (1.66) 15.36 (0.33)   .001Mean BCVA (SEM), logMAR units 0.66 (0.12) 0.78 (0.12) 0.001 0.59 (0.12) 0.70 (0.11)   .001 Visual field mean deviation (SEM), dB c  19.70 (0.96)   19.67 (0.95) 0.09   18.45 (1.11)   19.49 (1.17)   .001Mean no. of glaucoma medications (SEM) 2.8 (0.11) 1.03 (0.27)   0.001 2.7 (0.11) 1.41 (0.19)   .001BCVA   best-corrected visual acuity; dB  decibels; IOP  intraocular pressure; logMAR  logarithm of the minimal angle of resolution;SEM  standard error of the mean.  a Wilcoxon signed-rank test comparisons of postoperative month 24 and preoperative figures in each study group, post hoc study powersfor all significant comparisons were  80% (based on an  error of 0.05).  b P  .001, Mann–Whitney  U   test comparison of postoperative month 24 figures between the 2 study groups. c Three subjects in the Ahmed group and 5 in the Molteno group were excluded from visual field calculations because of the learning effect,reducing total number to 26 in the Ahmed group and 23 in the Molteno group. A MERICAN  J OURNAL OF  O PHTHALMOLOGY 896  J UNE 2010  chi-square and Fisher exact tests were used for qualitativevariables. To determine factors independently associatedwith IOP in postoperative month 24, multivariate analysiswas performed using a stepwise linear regression model of several variables. The cumulative probability of success wasanalyzed by Kaplan-Meier life-table analysis. As soon as aneye reached a failure end point, it was censored from furtheranalysis. Cox proportional hazards analysis was used to iden-tify independent predictors of surgical failures. Post hoc studypower for significant comparisons was calculated usingG*Power 3, a power analysis software. 22 P values less than .05were considered statistically significant.  FIGURE 3. Graph showing the preoperative and postoperative mean number of glaucoma medications in the Ahmed valve andMolteno implant groups. Note that comparisons at all time points between 2 groups were insignificant. FIGURE 4. Graph showing visual acuity in the Ahmed valve and Molteno implant groups. Note that comparisons at all time pointsbetween 2 groups were insignificant. logMAR  logarithm of the minimal angle of resolution. A HMED  V ALVE VS  M OLTENO  I MPLANT V OL .  149 , N O .  6  897
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