Postoperative Complications in the Tube Versus Trabeculectomy (TVT) Study During Five Years of Follow-up




Purpose


To describe postoperative complications encountered in the Tube Versus Trabeculectomy (TVT) Study during 5 years of follow-up.


Design


Multicenter randomized clinical trial.


Methods


settings: Seventeen clinical centers. study population: Patients 18 to 85 years of age who had previous trabeculectomy and/or cataract extraction with intraocular lens implantation and uncontrolled glaucoma with intraocular pressure (IOP) ≥18 mm Hg and ≤40 mm Hg on maximum tolerated medical therapy. interventions: Tube shunt (350-mm 2 Baerveldt glaucoma implant) or trabeculectomy with mitomycin C (MMC 0.4 mg/mL for 4 minutes). main outcome measures: Surgical complications, reoperations for complications, visual acuity, and cataract progression.


Results


Early postoperative complications occurred in 22 patients (21%) in the tube group and 39 patients (37%) in the trabeculectomy group ( P = .012). Late postoperative complications developed in 36 patients (34%) in the tube group and 38 patients (36%) in the trabeculectomy group during 5 years of follow-up ( P = .81). The rate of reoperation for complications was 22% in the tube group and 18% in the trabeculectomy group ( P = .29). Cataract extraction was performed in 13 phakic eyes (54%) in the tube group and 9 phakic eyes (43%) in the trabeculectomy group ( P = .43).


Conclusions


A large number of surgical complications were observed in the TVT Study, but most were transient and self-limited. The incidence of early postoperative complications was higher following trabeculectomy with MMC than tube shunt surgery. The rates of late postoperative complications, reoperation for complications, and cataract extraction were similar with both surgical procedures after 5 years of follow-up.


The Tube Versus Trabeculectomy (TVT) Study is a multicenter randomized clinical trial comparing the safety and efficacy of tube shunt surgery and trabeculectomy with mitomycin C (MMC). Our companion article reviews the outcomes of treatment in the TVT Study during 5 years of follow-up. Tube shunt surgery had a higher success rate than trabeculectomy with MMC during the first 5 years of the study. A higher rate of reoperation for glaucoma was observed after trabeculectomy with MMC compared with tube shunt surgery. Both surgical procedures had similar intraocular pressure (IOP) reduction and use of supplemental medical therapy at 5 years. Vision loss occurred at a similar rate following placement of a tube shunt and trabeculectomy with MMC.


A comparison of surgical procedures requires not only an assessment of efficacy, but also an evaluation of the incidence and severity of associated complications. Tube shunt surgery and trabeculectomy with MMC each has its own set of complications that may occur in the early or late postoperative periods. This article describes the postoperative complications encountered during 5 years of follow-up in the TVT Study and the management of these complications.


Methods


Study Design


The study protocol is described in detail in a previous publication. In brief, patients 18 to 85 years of age who had previous cataract extraction with intraocular lens implantation and/or trabeculectomy with IOP ≥18 mm Hg and ≤40 mm Hg on maximum tolerated medical therapy were enrolled in the study. Baseline demographic and clinical information were collected for each patient. One eye of each eligible patient was randomized to placement of a 350-mm 2 Baerveldt glaucoma implant (Abbott Medical Optics, Santa Ana, California, USA) or trabeculectomy with MMC (0.4 mg/mL for 4 minutes). Follow-up visits were scheduled at 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, 18 months, 2 years, 3 years, 4 years, and 5 years postoperatively. Each examination included measurement of Snellen visual acuity (VA), IOP, slit-lamp biomicroscopy, Seidel testing, and ophthalmoscopy. Humphrey perimetry, Early Treatment Diabetic Retinopathy Study (ETDRS) VA, and quality of life using the National Eye Institute Visual Function Questionnaire were evaluated at baseline and at the annual follow-up visits. Investigators provided an explanation for loss of 2 or more lines of Snellen VA at follow-up visits after 3 months. Failure was prospectively defined as IOP >21 mm Hg or less than 20% reduction below baseline on 2 consecutive follow-up visits after 3 months, IOP ≤5 mm Hg on 2 consecutive follow-up visits after 3 months, additional glaucoma surgery, or loss of light perception vision. Patients who underwent additional glaucoma surgery were censored from analysis of complications after the reoperation for glaucoma. The study was monitored by an independent Safety and Data Monitoring Committee.


Investigators in the TVT Study recorded postoperative interventions and complications on standardized forms at each follow-up visit. The data forms listed several complications that were required to be designated as present or absent, and blank spaces were also included for recording complications that did not appear on the list. Investigators were asked to report any complications that were present at the scheduled follow-up visit or between study visits. The definition of a complication was not standardized, and documentation of a complication was left to the discretion of the surgeon. Early postoperative complications were defined as surgical complications developing within the first month after randomized surgical treatment, and late postoperative complications were complications that occurred at least 1 month following glaucoma surgery. Surgical complications that developed during the first postoperative month and persisted with longer follow-up were counted only as early postoperative complications. The date and type of surgical treatment for any complications were recorded. Reoperation for a complication was defined as additional surgery requiring a return to the operating room to manage a surgical complication, such as a pars plana vitrectomy or penetrating keratoplasty. A vitreous tap with injection of intravitreal antibiotics for endophthalmitis was also counted as a reoperation for a complication. Interventions performed at the slit lamp, such as bleb needling for an encapsulated bleb or reformation of a shallow anterior chamber, were not considered reoperations. Persistent diplopia, persistent corneal edema, and dysesthesia were defined as the postoperative development of these complications and their presence at the 6-month follow-up visit or thereafter. Eyes that were Seidel positive within the first month of follow-up were classified as having wound leaks, and those that were Seidel positive after 1 month were categorized as having bleb leaks. Serious complications were defined as surgical complications that produced loss of 2 or more lines of Snellen VA and/or required reoperation to manage the complication. Cataracts were considered to have progressed if there was loss of 2 or more Snellen lines that was attributed to cataract at the 6-month follow-up visit or thereafter, or if cataract surgery was performed.


Statistical Analysis


Univariate comparisons between treatment groups were made using the 2-sided Student t test, χ 2 test, or Fisher exact test. The associations of surgical complications with treatment outcome, vision loss, and cataract progression were assessed for statistical significance with the χ 2 test or Fisher exact test. A P value of .05 or less was considered statistically significant.




Results


Recruitment and Surgical Treatment


A total of 212 eyes of 212 patients were enrolled in the TVT Study, including 107 patients who underwent placement of a tube shunt and 105 patients who had a trabeculectomy with MMC. All patients received their assigned treatment. Additional details on operative data and intraoperative complications were provided in a previous publication.


Postoperative Interventions


Table 1 lists postoperative interventions. Most interventions occurred in the early postoperative period and were previously reported. The frequency of postoperative interventions was significantly higher in the trabeculectomy group than in the tube group. A total of 34 interventions were performed in 27 patients (25%) in the tube group, and 105 interventions were made in 74 patients (70%) in the trabeculectomy group ( P < .001, χ 2 test). The most common postoperative intervention was laser suture lysis in 58 patients (55%) in the trabeculectomy group and rip cord removal in 19 patients (18%) in the tube group.



TABLE 1

Postoperative Interventions in the Tube Versus Trabeculectomy Study
























































Tube Group a (n = 107) Trabeculectomy Group a (n = 105)
Laser suture lysis 6 (6) 58 (55)
Removal of rip cord 19 (18)
5-FU injection 1 (1) 26 (25)
Needling 3 (3) 14 (13)
Anterior chamber reformation 4 (4) 0 (0)
Injection of intracameral tPA 1 (1) 2 (2)
Suture wound leak 0 1 (1)
Autologous blood injection 0 1 (1)
Selective laser trabeculoplasty 0 1 (1)
YAG to internal ostium 1 (1)
YAG vitreolysis 0 1 (1)
Total number of patients with postoperative interventions b 27 (25) 74 (70)

5-FU = 5-fluorouracil; tPA = tissue plasminogen activator; YAG = yttrium-aluminum-garnet.

a Data are presented as number (percentage).


b P < .001 for the difference in total number of patients with postoperative interventions between treatment groups (χ 2 test).



Some interventions occurred in the late postoperative period. There were 2 patients in the tube group who had interventions at least 1 year after surgery, 1 requiring injection of intracameral tissue plasminogen activator for tube obstruction following a penetrating keratoplasty and 1 patient with elevated IOP requiring bleb needling. Interventions were performed after the first postoperative year in 11 patients in the trabeculectomy group; interventions included laser suture lysis in 1 patient for elevated IOP, an autologous blood injection in 1 patient for a late-onset bleb leak, yttrium-aluminum-garnet (YAG) vitreolysis in 1 patient with vitreous incarceration in the internal ostium, selective laser trabeculoplasty in 1 patient for elevated IOP, and YAG laser treatment to the internal ostium in 1 patient with a failing bleb. There were 6 additional patients who underwent needling procedures, including 1 patient for an encapsulated bleb and 5 patients for a flat bleb. A subconjunctival 5-fluorouracil (5-FU) injection was administered in conjunction with the needling procedure in 3 patients. In the trabeculectomy group, placement of a tube shunt was ultimately performed as a reoperation for glaucoma in 2 patients who had needling procedures and in the patient who underwent YAG laser treatment to the internal ostium. The patient who received an autologous blood injection subsequently had a bleb revision for a persistent bleb leak.


Early Postoperative Complications


Table 2 shows early postoperative complications developing within the first month after surgery. Early postoperative complications occurred with significantly greater frequency in the trabeculectomy group compared with the tube group. A total of 35 early postoperative complications were reported in 22 patients (21%) in the tube group, and 51 complications were noted in 39 patients (37%) in the trabeculectomy group ( P = .012, χ 2 test). Among the 21 patients with a shallow or flat anterior chamber, 10 patients had associated choroidal effusions, 4 patients had aqueous misdirection, and 3 patients had suprachoroidal hemorrhages. There were 37 patients who had only 1 early postoperative complication. Several patients developed multiple early postoperative complications, including 23 patients with 2 complications and 1 patient with 3 complications.



TABLE 2

Early Postoperative Complications a in the Tube Versus Trabeculectomy Study
















































Tube Group b (n = 107) Trabeculectomy Group b (n = 105)
Choroidal effusion 15 (14) 14 (13)
Shallow or flat anterior chamber 11 (10) 10 (10)
Wound leak 1 (1) 12 (11)
Hyphema 2 (2) 8 (8)
Aqueous misdirection 3 (3) 1 (1)
Suprachoroidal hemorrhage 2 (2) 3 (3)
Vitreous hemorrhage 1 (1) 1 (1)
Decompression retinopathy 0 1 (1)
Cystoid macular edema 0 1 (1)
Total number of patients with early postoperative complications c d 22 (21) 39 (37)

a Onset ≤1 month.


b Data presented as number of patients (percentage).


c Some patients had more than 1 complication.


d P = .012 for the difference in total number of patients with early postoperative complications between treatment groups (χ 2 test).



Wound leak was the only early postoperative complication that was significantly more common in the trabeculectomy group compared with the tube group ( P = .004, χ 2 test). No early postoperative complications occurred with significantly greater frequency in the tube group than in the trabeculectomy group. A tendency toward a higher incidence of hyphema in the trabeculectomy group relative to the tube group was observed, but the difference was not statistically significant ( P = .058, Fisher exact test).


Late Postoperative Complications


Table 3 reviews late postoperative complications occurring more than 1 month after surgery. The overall incidence of late postoperative complications was similar between treatment groups. A total of 47 late postoperative complications were seen in 36 patients (34%) in the tube group, and 50 complications were observed in 38 patients (36%) in the trabeculectomy group ( P = .81, χ 2 test). A single late postoperative complication developed in 56 patients. Other patients experienced multiple late postoperative complications, including 14 patients with 2 complications, 3 patients with 3 complications, and 1 patient with 4 complications.



TABLE 3

Late Postoperative Complications a in the Tube Versus Trabeculectomy Study








































































Tube Group b c (n = 107) Trabeculectomy Group b c (n = 105)
Persistent corneal edema 17 (16) 9 (9)
Dysesthesia 1 (1) 8 (8)
Persistent diplopia 6 (6) 2 (2)
Encapsulated bleb 2 (2) 6 (6)
Bleb leak 0 6 (6)
Choroidal effusion 2 (2) 4 (4)
Cystoid macular edema 5 (5) 2 (2)
Hypotony maculopathy 1 (1) 5 (5)
Tube erosion 5 (5)
Endophthalmitis/blebitis 1 (1) 5 (5)
Chronic or recurrent iritis 2 (2) 1 (1)
Tube obstruction 3 (3)
Retinal detachment 1 (1) 1 (1)
Corneal ulcer 0 1 (1)
Shallow or flat anterior chamber 1 (1) 0
Total number of patients with late postoperative complications d e 36 (34) 38 (36)

a Onset >1 month.


b Data censored after a reoperation for glaucoma.


c Data presented as number of patients (percentage).


d Some patients had more than 1 complication.


e P = .81 for the difference in total number of patients with late postoperative complications between treatment groups (χ 2 test).



Several patients in each treatment group developed both early and late postoperative complications. The overall rate of postoperative complications was significantly higher in the trabeculectomy group compared with the tube group. During 5 years of follow-up, 46 patients (43%) in the tube group and 66 patients (63%) in the trabeculectomy group experienced 1 or more surgical complications postoperatively ( P = .006, χ 2 test).


Bleb leak ( P = .014, Fisher exact test) and dysesthesia ( P = .018, Fisher exact test) were late postoperative complications that occurred with significantly greater frequency in the trabeculectomy group than in the tube group. No late postoperative complications were significantly more common in the tube group compared with the trabeculectomy group.


Reoperation for Complications


Table 4 presents the reoperations that were performed for complications. A total of 20 patients in the tube group and 15 patients in the trabeculectomy group underwent additional surgery to manage postoperative complications. The 5-year cumulative reoperation rate for complications from Kaplan-Meier survival analysis was 22% in the tube group and 18% in the trabeculectomy group, a difference that was not statistically significant ( P = .29, log-rank test adjusted for stratum). There were 6 patients in the tube group and 5 patients in the trabeculectomy group who had persistent corneal edema requiring a penetrating keratoplasty. One of these patients in the tube group underwent a repeat penetrating keratoplasty and, later, a pars plana vitrectomy for vitreous obstruction of the tube in the study eye. An additional patient in the tube group had a penetrating keratoplasty in conjunction with repositioning of the tube. A pars plana vitrectomy was performed in 6 patients in the tube group, including 2 patients for aqueous misdirection, 2 patients for tube obstruction by vitreous, 1 patient for endophthalmitis, and 1 patient for a retinal detachment. Revision of the tube shunt with placement of a new patch graft was performed in 5 patients in the tube group for tube erosion, which included 1 patient who initially had this procedure in conjunction with cataract extraction. The patient who had a tube shunt revision and cataract surgery developed a recurrent erosion requiring a second tube revision with patch graft. Another patient needed a repeat tube shunt revision, followed by removal of the tube shunt for repeated exposure. There were 5 patients in the trabeculectomy group who underwent a bleb revision, including 4 patients for bleb leaks and 1 patient for hypotony maculopathy. The patient with hypotony maculopathy subsequently had a trabeculectomy revision and placement of a 350-mm 2 Baerveldt glaucoma implant. Drainage of a choroidal effusion was performed in 2 patients in the tube group and 1 patient in the trabeculectomy group. The 2 patients in the tube group who had choroidal drainage later had additional surgery for other complications, including a penetrating keratoplasty for corneal edema in 1 patient and a pars plana vitrectomy to repair a retinal detachment in the other patient. There were 2 patients in the tube group and 1 patient in the trabeculectomy group who underwent a Descemet stripping automated endothelial keratoplasty (DSAEK) for persistent corneal edema. Tube repositioning was performed in 1 patient in the tube group for corneal edema, and a DSAEK was subsequently done for persistent corneal edema. Bleb-related endophthalmitis was treated with a vitreous tap with injection of intravitreal antibiotics in 2 patients in the trabeculectomy group. Drainage of a suprachoroidal hemorrhage was performed in 1 patient in the trabeculectomy group, and 1 patient in the tube group had lysis of iris adhesions obstructing the tube combined with cataract extraction.



TABLE 4

Reoperations for Complications in the Tube Versus Trabeculectomy Study




































































Tube Group a (n = 107) Trabeculectomy Group a (n = 105)
Penetrating keratoplasty 6
Pars plana vitrectomy 6 0
Tube shunt revision with patch graft 5
Bleb revision 0 5
Drainage of choroidal effusion 2 1
DSAEK 2 1
Vitreous tap with injection of intravitreal antibiotics 0 2
Penetrating keratoplasty and tube repositioning 1
Tube repositioning 1
Drainage of suprachoroidal hemorrhage 0 1
Lysis of iris adhesions to tube and cataract extraction 1
Tube revision with patch graft and cataract extraction 1
Removal of tube shunt 1
Trabeculectomy revision and tube shunt 0 1
Total number of patients (cumulative percentage) with reoperations for complications b c 20 (22) 15 (18)

DSAEK = Descemet stripping automated endothelial keratoplasty.

a Data censored after a reoperation for glaucoma.


b Some patients had more than 1 type of reoperation for complications.


c P = .29 for the difference in 5-year cumulative reoperation rates for complications between treatment groups from Kaplan-Meier analysis (log-rank test adjusted for stratum).



Serious Complications


Table 5 shows serious complications resulting in reoperation and/or vision loss. The incidence of serious complications was similar between treatment groups. Serious complications were observed in 24 patients (22%) in the tube group and 21 patients (20%) in the trabeculectomy group ( P = .79, χ 2 test). Persistent corneal edema was the most common cause for both reoperation for a complication and loss of 2 or more lines of Snellen VA in the tube and trabeculectomy groups. Reoperations for 2 different complications were performed in 3 patients in the tube group, including 1 patient who had a pars plana vitrectomy for tube obstruction by vitreous and a subsequent penetrating keratoplasty for corneal edema, 1 patient who underwent drainage of a choroidal effusion followed by a penetrating keratoplasty for corneal edema, and 1 patient who had drainage of a choroidal effusion and later a pars plana vitrectomy for a retinal detachment. One patient in each treatment group experienced loss of 2 or more Snellen lines from 2 postoperative complications, including a patient in the tube group who had a suprachoroidal hemorrhage and retinal detachment and a patient in the trabeculectomy group who had endophthalmitis and cystoid macular edema. A total of 11 patients in the tube group and 7 patients in the trabeculectomy group underwent a reoperation to manage a complication and also suffered vision loss.



TABLE 5

Serious Complications Associated With Reoperation and/or Vision Loss in the Tube Versus Trabeculectomy Study




















































































Tube Group a (n = 107) Trabeculectomy Group a (n = 105)
Reoperation for complications, n (%) 20 b (19) 15 (14)
Persistent corneal edema 9 6
Tube erosion 5
Bleb leak 0 4
Choroidal effusion 2 1
Endophthalmitis 1 2
Tube obstruction 3
Aqueous misdirection 2 0
Hypotony maculopathy 0 1
Suprachoroidal hemorrhage 0 1
Retinal detachment 1 0
Vision loss of ≥2 Snellen lines, n (%) 15 c (14) 13 c (12)
Persistent corneal edema 13 7
Suprachoroidal hemorrhage 1 2
Endophthalmitis 1 1
Hypotony maculopathy 0 2
Retinal detachment 1 1
Cystoid macular edema 0 1
Total number (%) of patients with serious complications d e 24 (22) 21 (20)

a Data censored after a reoperation for glaucoma.


b Three patients had reoperations for 2 different complications.


c One patient had 2 different complications producing vision loss.


d Some patients had both a reoperation for a complication and vision loss.


e P = .79 for the difference in serious complication rates between treatment groups (χ 2 test).



Vision Loss Associated With Postoperative Complications


Table 6 shows visual acuity results in patients with and without postoperative complications. A significant decrease in Snellen and ETDRS VA was observed in patients who did and did not experience postoperative complications. ETDRS and Snellen VA were similar between patients with and without complications at 5 years, and no significant difference in the rate of loss of 2 or more Snellen lines was seen between these groups after 5 years of follow-up.



TABLE 6

Visual Acuity Results in the Tube Versus Trabeculectomy Study

















































































Patients With Complications Patients Without Complications
Tube Group Trabeculectomy Group Overall Group Tube Group Trabeculectomy Group Overall Group P Value a
ETDRS VA, mean ± SD (n)
Baseline 61 ± 24 (46) 65 ± 18 (66) 63 ± 21 (112) 64 ± 24 (61) 64 ± 22 (39) 64 ± 23 (100) .89 b
5 years 33 ± 31 (18) 56 ± 26 (30) 47 ± 30 (48) 46 ± 36 (19) 44 ± 30 (11) 46 ± 33 (30) .80 b
Snellen VA, logMAR mean ± SD (n)
Baseline .46 ± 54 (46) .36 ± .36 (66) .40 ± .44 (112) .39 ± .55 (61) .38 ± .41 (39) .39 ± .50 (100) .80 b
5 years .96 ± 1.00 (34) .70 ± .79 (49) .81 ± .88 (83) .74 ± .94 (33) .54 ± .61 (27) .65 ± .81 (60) .29 b
Loss of ≥2 Snellen lines, n (%) 18 d (51%) 22 (45%) 40 (48%) 13 (39%) 11 (41%) 24 (40%) .46 c

ETDRS = Early Treatment Diabetic Retinopathy Study; SD = standard deviation; VA = visual acuity.

a P value comparing the overall groups with and without complications.


b Student t test.


c χ 2 test.


d One patient who did not have Snellen VA measured at 5 years was determined to have lost >2 Snellen lines based on change in ETDRS VA.



The relationship between postoperative complications and vision loss was explored, and the results are presented in Table 7 . The presence of any postoperative complication did not significantly increase the rate of loss of 2 or more Snellen lines ( P = .46, χ 2 test), and the number of complications was not significantly associated with vision loss. Examination of the individual complications listed in Tables 2 and 3 revealed that only persistent corneal edema significantly predicted vision loss in univariate ( P = .001, χ 2 test) and multivariate ( P < .001, logistic regression) analyses. Vision was reduced in 17 of 21 patients (81%) with corneal edema and in 47 of 123 patients (38%) without corneal edema.



TABLE 7

Association of Surgical Complications With Treatment Outcome, Vision Loss, and Cataract Progression in the Tube Versus Trabeculectomy Study























































































































Treatment Outcome a Vision Loss b Cataract Progression c
Success d (n = 91) Failure d (n = 66) P Value Stable Vision d (n = 80) Loss of ≥2 Snellen Lines d (n = 64) P Value Stable d (n = 8) Progressed d (n = 31) P Value
Any postoperative complication
No 39 (43) 28 (42) >.99 e 36 (45) 24 (38) .46 e 7 (88) 15 (48) .11 g
Yes 52 (57) 38 (58) 44 (55) 40 (63) 1 (13) 16 (52)
Number of postoperative complications
0 39 (43) 28 (42) >.99 f 36 (45) 24 (38) .092 f 7 (88) 15 (48) .15 f
1 29 (32) 19 (29) 27 (34) 20 (31) 0 8 (26)
2 14 (15) 14 (21) 13 (16) 11 (17) 1 (13) 4 (13)
3 5 (5) 4 (6) 3 (4) 6 (9) 0 1 (3)
4 4 (4) 1 (2) 1 (1) 3 (5) 0 3 (10)

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Jan 12, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Postoperative Complications in the Tube Versus Trabeculectomy (TVT) Study During Five Years of Follow-up
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