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Failed Ahmed glaucoma valves: trabeculectomy versus repeat shunt surgery

BMC Ophthalmology volume 24, Article number: 367 (2024) Cite this article

Abstract

Introduction

To investigate the outcomes of trabeculectomy (TRAB) versus repeat Ahmed glaucoma valve (re-AGV) implantation in eyes with Ahmed glaucoma valve (AGV) failure.

Methods

This quasi-experimental study includes patients with failed AGV implants requiring additional surgical intervention between 2018 and 2022. Patients in the TRAB group underwent a fornix-based procedure with mitomycin C 0.01% injection (0.1 mL). Eyes in the re-AGV group underwent repeat shunt surgery. The choice of the procedure was based on conjunctival condition. The primary outcome measure was surgical success rate based on various intraocular pressure (IOP) targets and percentages of IOP reduction from baseline: IOP ≤ 21 mmHg and 20% reduction (conventional criteria), IOP ≤ 18 and > 20% reduction (criterion A), IOP ≤ 15 and > 25% reduction (criterion B), and IOP ≤ 12 and > 30% reduction (criterion C).

Results

Forty-eight eyes of 48 patients were operated and reported herein, consisting of 22 eyes of 22 patients undergoing TRAB and 26 eyes of 26 subjects undergoing re-AGV. No significant difference was observed between the study groups in terms of initial diagnoses, baseline IOP or the number of prior surgeries. The cumulative probability of survival at one year was significantly higher in the trabeculectomy group using the three stricter success definitions. In both study groups, IOP was significantly reduced from baseline at all postoperative visits, and was significantly lower in the TRAB group at all time points beyond one month. At 12 months, 5% of TRAB versus 48% of re-AGV eyes required glaucoma medications (P < 0.001). The rate of complications was comparable between the study groups (P = 0.76) but there was a trend toward a greater need for repeat surgery in the re-AGV group (4 eyes versus nil, P = 0.07).

Conclusions

Trabeculectomy can be considered a safe and effective surgical option in eyes with failed AGV leading to significantly lower IOP levels and more favorable success rates than re-AGV in selected patients.

Key message

AbstractSection What is known:

•Patients with acceptable conjunctival quality and mobility, both trabeculectomy and re-AGV are effective in reducing IOP after a failed AGV implant.

•Repeat GDD implantation, as the most commonly adopted strategy, carries a significant risk of complications including ocular dysmotility, cosmetic issues and corneal decompensation.

AbstractSection What is new:

•Trabeculectomy could be a viable option if the conjunctiva has not been violated extensively during primary shunt implantation or prior procedures.

•Trabeculectomy might be superior to re-AGV in terms of level of IOP and number of glaucoma medications in selected patients.

Peer Review reports

Introduction

Glaucoma is a major cause of irreversible blindness and requires life-long management. The Ahmed glaucoma valve (AGV) is one of the most commonly used glaucoma drainage devices (GDDs) in current practice [1], mostly reserved for intractable cases with advanced glaucoma and history of multiple procedures including prior failed glaucoma operations. The cumulative probability of failure for AGV has been about 40% at five years according to the ABC study [2].

It has been estimated that the majority of glaucoma patients need repeat surgery within 20 years of the first operation [3]. In patients with initial GDD failure, conventional surgical options include capsulectomy shunt revision [4], repeat GDD implantation, or cyclodestructive procedures; however the choice among these options may pose a challenge for glaucoma surgeons. Among the mentioned modalities, repeat GDD implantation is the most commonly adopted strategy [5,6,7,8], however it carries a significant risk of corneal decompensation in the long term [9,10,11]. Considering the drawbacks to the mentioned conventional options, over the past few years our group has performed trabeculectomy in selected cases after initial AGV failure.

In the present study, we report the outcomes of trabeculectomy in eyes with AGV failure in which the procedure was technically feasible and compare it with the more conventional approach of performing repeat AGV implantation.

Methods

This quasi-experimental study includes patients with a failed AGV (Model FP7; New World Medical, Rancho Cucamonga, LA, USA) at least six months after device implantation. We recruited patients referred to Labbafinejad University Hospital (a tertiary center affiliated with Shahid Beheshti University of Medical Sciences, Tehran, Iran) within a four-year timeframe – January 2018 to July 2022. AGV failure was defined as unacceptable intraocular pressure (IOP) on two consecutive visits (one to two weeks apart) despite using maximum tolerable glaucoma medications. All initial AGVs had been implanted in the superotemporal quadrant. Exclusion criteria consisted of lack of adequate conjunctiva in the superior quadrants, active neovascular glaucoma, and glaucoma associated with iridocorneal endothelial syndrome and fibrous or epithelial down growth. The current study follows the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board at Shahid Beheshti University of Medical Sciences (Ethics code: IR.SBMU.ORC.REC.1402.003). Written informed consent for surgery was obtained from all study participants or their legal guardians.

Patients were scheduled for trabeculectomy or re-AGV based on conjunctival appearance and mobility in the superonasal quadrant. If the conjunctiva was mobile with no significant scars or sub-conjunctiva fibrosis, the ocular surface condition was favorable, the angle was open on gonioscopy, the eye was quiescent and had no history of vitroretinal surgery, trabeculectomy was considered; otherwise the patient would be scheduled for re-AGV.

Surgical technique

All procedures were performed by experienced glaucoma surgeons in the same standardized fashion. Trabeculectomy was performed employing a fornix-based approach: Mitomycin C (MMC, 0.01% concentration, 0.1mL,) was injected into the subtenon space in at the beginning of surgery taking care to diffuse the injected volume at and posterior to the surgical site [12,13,14]. Peritomy was performed in the superonasal quadrant. The conjunctiva and Tenon were dissected and undermined. A 4 mm-based half-thickness trapezoidal scleral flap was fashioned at the limbus, a 1.0 × 1.5 mm inner block was removed followed by peripheral iridectomy. The scleral flap was closed with two releasable 10 − 0 nylon sutures and after titrating filtration, the conjunctiva was sutured to the limbus on both sides using 10 − 0 nylon sutures. The releasable sutures were removed after the operation according to IOP and bleb morphology. In the re-AGV group, an incision was made through the superonasal conjunctiva and tenon’s capsule, 4 mm posterior to the limbus. Tenon’s capsule was dissected from the sclera using Westcott scissors to provide space for plate insertion. The AGV (model FP7, New World Medical, Rancho Cucamonga, LA, USA) was primed with 2 mL of balanced saline solution and gently passed through the incision into the subtenon space. The plate was sutured to the sclera 8–10 mm posterior to the limbus using 7 − 0 silk sutures. Triamcinolone acetonide (10 mg) was injected in the sub-tenon space around the AGV plate [15]. The tube was trimmed bevel-up with an estimated intracameral length of 2 mm and inserted into the anterior chamber 1 mm posterior to the limbus. The tube was fixed to the sclera and covered with donor sclera [16]. Tenon and conjunctiva were repaired using 10 − 0 nylon sutures.

The postoperative regimen consisted of chloramphenicol 0.5% eye drops (Sina Darou Laboratories Co, Tehran, Iran) four times daily for one week and betamethasone (Sina Darou Laboratories Co, Tehran, Iran) 6 times per day, tapered off over 3 months.

Data collection

Patients were followed on days 1 and 3, weeks 1, 2 and 4, monthly up to three months after surgery and then at 3 month intervals. Additional visits were scheduled based on clinical conditions. IOP measurement, slit lamp biomicroscopy and funduscopy were performed at each follow-up and data including IOP, number of medications and complications were recorded.

The primary outcome measure was qualified success rates (with or without medications), based on different IOP targets and percentages of reduction. IOP ≤ 21 mmHg and 20% IOP reduction was adopted as the conventional success definition as in other glaucoma studies. In addition, three other success criteria were used: IOP ≤ 18 and > 20% reduction (criterion A), IOP ≤ 15 and > 25% reduction (criterion B), and IOP ≤ 12 and > 30% reduction (criterion C) (Table 1) [17]. Loss of light perception and need for further glaucoma surgery were also considered as failure criteria.

Table 1 Criteria used to define success for trabeculectomy versus repeat AGV implantation
Full size table

Statistical analysis

To describe data, mean, frequency and standard deviation were used. The normality of data was tested using Shapiro-Wilk test. IOP was compared between groups using Mann-Whitney and within groups using linear mixed models corrected by Bonferroni for multiple comparisons. In the trabeculectomy group, the association between previous failed trabeculectomy and the success of re-trabeculectomy after AGV failure was assessed using Fisher’s exact test. All analyses were performed using SPSS software (Version 25.0, IBM Corp, Armonk, NY, USA).

Results

Baseline characteristics

A total of 48 eyes of 48 patients were included in the study: twenty-two eyes of 22 patients underwent trabeculectomy (TRAB) and 26 eyes of 26 other subjects underwent repeat AGV implantation (re-AGV). The two groups were comparable (Table 2) regarding age, glaucoma diagnoses, baseline IOP levels and number of prior procedures (1.3 ± 0.6 in the TRAB vs. 1.4 ± 0.6 in the re-AGV groups, P = 0.67). However, prior vitreoretinal surgery and lensectomy were more common in the re-AGV group. (Table 2). Ten subjects in the TRAB group and 14 patients in the re-AGV group had been diagnosed with primary congenital or juvenile glaucoma. (P = 0.22) All of them had history of trabeculotomy, trabeculectomy or a combination thereof in childhood.

Table 2 Baseline characteristics of the study groups
Full size table

Success rates

The cumulative probability of survival at year 1 was higher in the trabeculectomy group using all four success definitions. Significant differences were observed only using the stricter criteria A, B and C. History of trabeculotomy or trabeculectomy in childhood had no association with trabeculectomy success. Success rates and outcomes are summarized in Table 3 and demonstrated in Fig. 1.

Table 3 Cumulative probability of survival and mean duration of survival (days) in the study groups based on different success definitions
Full size table
Fig. 1
figure 1

A: Kaplan-Meier curve based on conventional criterion for success B: Kaplan-Meier curve based on success criterion A C: Kaplan-Meier curve based on success criterion B D: Kaplan-Meier curve based on success criterion C

Full size image

IOP outcome

In the TRAB group, mean IOP was 30.5 ± 7.5 at baseline and reached 8.5 ± 2 mmHg at one year. (P < 0.001). Corresponding values in the re-AGV group were 32.6 ± 7.1 and 14.4 ± 4.3 mmHg, respectively. (P < 0.001) IOP was significantly lower in the TRAB group as compared to the re-AGV group at 3, 6, 9 and 12 months. (Table 4,).

Table 4 Intraocular pressure in the study groups during the follow-up period
Full size table

Glaucoma medications

At baseline, the average number (median) of glaucoma medications was 4.18 ± 0.79 (4.0) versus 3.5 ± 0.64 (3.0) in the trabeculectomy and re-AGV groups, respectively (P = 0.95). The mean number of glaucoma medication was 0.05 ± 0.22 and 1.3 ± 1.5 after 12 months in TRAB and re-AGV group, respectively. (P = 0.86). 5% (2/26) versus 48% (11/23) of patients in the trabeculectomy and re-AGV groups required glaucoma medications at 12 months, respectively (P < 0.001).

Complications

There was no significant difference in the total rate of complications between the study groups (P = 0.92). In the trabeculectomy group, early leakage developed in two patients which resolved with conservative measures. Avascular blebs were observed in two other patients. One eye developed a significant hyphema and underwent AC washing. In the re-AGV group, tube exposure occurred in two eyes requiring donor scleral patch grafts and conjunctival repair, and two eyes underwent DSAEK due to corneal decompensation (Table 5). No patient experienced visually devastating complications including persistent hypotony, suprachoroidal hemorrhage, endophthalmitis, or phthisis bulbi. Repeat glaucoma surgery was required in no patient in the trabeculectomy group versus 4 patients in the re-AGV group (P = 0.07). A third AGV was implanted in three of these patients, while CPC was performed for another patient.

Table 5 Complications in the study groups
Full size table

Discussion

The results of the current study showed that in patients with acceptable conjunctival quality and mobility [2] both TRAB and re-AGV are effective in reducing IOP after a failed AGV implant. However, TRAB was superior to re-AGV in terms of IOP control and glaucoma medications at all time points. Stricter success criteria also revealed the superior outcome of trabeculectomy over re-AGV. Lower IOP is definitely advantageous in eyes with advanced glaucomatous damage and a failed AGV.

After AGV failure, conventional options include repeat shunt implantation [5, 6, 9], capsulectomy shunt revision [4, 11, 18], and cyclodestructive procedures [19]. Among these, second shunt procedures have shown promising results in various short-term reports [7, 8], however, corneal decompensation has been reported frequently in adult cases following sequential tubes in long-term [11, 20]. Furthermore, the success rates of second shunts has been modest in childhood glaucoma with common tube-related complications [21]. Capsulectomy shunt revision, although an option in selected cases with poor conjunctiva, has a lower efficacy compared to repeat shunt implantation [11, 18]. Cyclodestructive procedures are a less attractive choice due to risks of postoperative inflammation, cystoid macular edema and vision loss [22].

Although trabeculectomy appears to be decreasing in frequency in favor of newer procedures, from a cost and public health standpoint, it still remains a standard procedure when low target pressure is required [23]. Trabeculectomy has passed the test of time for glaucoma surgeons and its efficacy has been improved by ongoing modifications and reduced complication rates [24]. A successful trabeculectomy could be a lasting solution for challenging cases glaucoma with failed prior surgeries.

The rationale behind this study was to determine the procedure of choice (trabeculectomy versus repeat AGV) based on several factors. To select trabeculectomy after a failed AGV, factors such as initial glaucoma diagnosis, conjunctival condition, ocular surface status, an open-angle on gonioscopy, quiescent eye, availability for follow-up and surgeon experience and skill should be considered. One of the largest drawbacks to implantation of a second tube shunt, besides ongoing endothelial cell loss, is that implantation of another GDD in the superonasal quadrant precludes the chance of future trabeculectomy.

Conventionally, GDD implantation is performed after trabeculectomy failure or as initial surgery in eyes at high risk of trabeculectomy failure. Nevertheless, with the results reported from the Tube Versus Trabeculectomy (TVT) Study endorsing “the sooner, the better” approach for implanting GDDs, and the fact that GDD implantation calls for less finesse than trabeculectomy and requires less vigilant postoperative care, a change in practice patterns and a growth in the number of GDDs is being observed [25, 26]. Trabeculectomy however could be a viable option if the conjunctiva was not violated extensively during primary shunt implantation. In countries with limited health resources and barriers to timely glaucoma detection [27, 28], a low-cost procedure that provides single-digit IOP would be sight-saving for patients with advanced disease.

Our success rates with repeat AGV after a failed shunt are similar to previous studies [6,7,8,9]. The results of the current study in the TRAB arm are also in line with a report by Alizadeh et al. [17]. They retrospectively reported the outcomes of trabeculectomy after a failed glaucoma shunt in 20 eyes for an average period of 3.7 years and showed that trabeculectomy was a viable option for uncontrolled IOP after GDD implantation. Mean IOP had been 19.3 ± 4.2 mm Hg in the mentioned report which was decreased to 9.8 ± 2.2 mm Hg in the first year. In the TRAB group in our study, mean preoperative IOP was 30.5 ± 7.5 mm Hg which was decreased to 8.5 ± 2 after 1 year.

In the TRAB group of the current series, we had 7 patients with history of failed trabeculectomy before initial AGV surgery who satisfied all success criteria at the end of follow-up. This finding is different from results from previously published studies reporting lower success with repeat trabeculectomy [29,30,31]. Such differences may be attributed to technical differences such as new site trabeculectomy in our study versus same-site repeat trabeculectomy by Hirunpatravong et al. [29], and method of MMC application [30]. Furthermore, the favorable success of trabeculectomy in our study could also be attributed to better conjunctival quality, as there was no history of prior vitreoretinal surgery in this group. Therefore, one should be cautious in generalizing these observations.

Trabeculotomy, trabeculectomy or a combination of both had been performed in childhood in patients with primary congenital [4] or juvenile glaucoma who made up close to 50% of the study population in our series. Based on our results however, these diagnoses and the mentioned procedures did not seem to affect the success of post-AGV trabeculectomy. The vigorous healing process in childhood contributes to the notoriously high risk of failure of trabeculectomy in childhood. One may speculate that the healing process might be less robust after trabeculectomy in adulthood and thus justify the outcomes we have observed.

No devastating complications were observed in our study. The most common complication following trabeculectomy after a failed shunt was hypotony maculopathy in the study by Alizadeh et al. [17], however we had no case of persistent hypotony, defined as IOP ≤ 5mmHg more than 4 weeks after surgery-in our patients. This might be explained by differences in the concentration and method of MMC application and also higher rate of primary GDD implantation in the mentioned study as compared to the current report (90% versus 54.55%).

The current study is limited by its non-randomized design. However, one should keep in mind that patients with failed GDDs represent a heterogeneous group of patients often with advanced glaucomatous damage and history of several operations including glaucoma surgery in whom the decision to perform another procedure is challenging and needs to be individualized. Keeping all of these factors in mind, devising a randomized clinical trial for such subjects may be impractical or unethical.

The patient population in this study reflects a real-world situation for glaucoma surgeons. The results might encourage opting for trabeculectomy over re-AGV in selected patients which seems to offer lower IOP levels and fewer medications. This is advantageous in patients with typically advanced damage, poor ocular surface conditions and limited tolerance to topical glaucoma medications. The success of trabeculectomy in such a setting is highly dependent on proper patient selection.

Data availability

The data is available upon the request from the corresponding author.

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Authors and Affiliations

  1. Ophthalmic Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran

    Neda Einollahi, Azadeh Doozandeh, Farideh Sharifipour, Kiana Hassanpour, Javad Rezaei, Hamed Radmehr & Shahin Yazdani

  2. Department of Ophthalmology, Labbafinejad Medical Center, Shahid Beheshti University of Medical Sciences, Paydarfard St. Boostan 9 St., Pasdaran Ave., Tehran, 16666-94516, Iran

    Neda Einollahi, Azadeh Doozandeh, Farideh Sharifipour, Kiana Hassanpour, Javad Rezaei, Hamed Radmehr & Shahin Yazdani

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Contributions

NE gathered the data, and wrote the main manuscript text; AD, FS, and SH generated the idea, performed the surgeries, gathered the data, and revised the manuscript. KH analyzed the data and drafted the manuscript. HR and JR helped with data gathering, analysis, and revision of the manuscript.

Corresponding author

Correspondence to Shahin Yazdani.

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Ethics approval and consent to participate

The study protocol was approved by the Institutional Review Board affiliated with the Shahid Beheshti University of Medical Sciences in Tehran, Iran. The protocol of the study adhered to the declaration of Helsinki, and an informed consent was obtained from all patients.

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Not Applicable.

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The authors declare no competing interests.

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Einollahi, N., Doozandeh, A., Sharifipour, F. et al. Failed Ahmed glaucoma valves: trabeculectomy versus repeat shunt surgery. BMC Ophthalmol 24, 367 (2024). https://doi.org/10.1186/s12886-024-03610-7

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