Outcome of Ahmed glaucoma valve implant in congenital fibrovascular pupillary membrane with secondary glaucoma

Abstract

Background

Congenital fibrovascular pupillary membranes in secondary glaucoma (CFPMSG) is kind of refractory childhood glaucoma. The aim of the study is to evaluate the efficacy and safety of Ahmed glaucoma valve (AGV) implants in CFPMSG.

Methods

Twelve patients with CFPMSG who underwent anterior chamber reconstruction (ASR) with a stable anterior chamber but uncontrolled intraocular pressure (IOP) underwent AGV implantation. Patients with a follow-up period of > 12 months were enrolled. Demographic data were collected. All patients underwent comprehensive ophthalmic examinations before and after surgeries, including IOP measurement, A- and B-scan ultrasonography, and ultrasound biomicroscopy (UBM), etc. Success was defined as postoperative intraocular pressure (IOP) ≤ 21 mmHg with (qualified success) or without (complete success) the use of glaucoma drugs.

Results

The median age of enrolled patients was 15.1 ± 12.5 months old (range 4.5–46) and 58.3% of them were female. At last follow-up (32.0 ± 16.0 months), the average IOP was declined (postoperative: 18.7 ± 4.5 mmHg vs. preoperative: 29.0 ± 4.0 mmHg, p < 0.001). The number of glaucoma drugs decreased from 3 (range 2–3) to 1.5 (range 0–3) (P < 0.001), while the anterior chamber depth (ACD) remained stable (3.21 ± 0.70 mm and 3.40 ± 0.82 mm, respectively) (p = 0.57) after AGV implantation. The complete success rate was 25% (3/12) and the qualified success rate was 58.3% (7/12). The total success rate was 83.8%. No severe complications were noted.

Conclusions

This study demonstrated that AGV implants could be safe and effective for CFPMSG with uncontrolled IOP. AGV implantation is a feasible option for the treatment of CFPMSG.

Background

Congenital fibrovascular pupillary membrane (CFPM) is a rare anterior segment disorder (ASD), with distinctive features of white pupillary fibrovascular membranes adhering to the iris and anterior capsule of the lens in the unilateral eye [1, 2]. CFPM with secondary glaucoma (CFPMSG) is a more serious ASD caused by pupillary block by the CFPM, resulting in uncontrolled and progressively increased intraocular pressure (IOP) that can lead to severe and sometimes irreversible vision loss [3, 4]. However, previous studies have not used ultrasound biomicroscopy (UBM) as a routine examination, making the choice of treatment difficult. Various approaches to treat CFPMSG, including peripheral iridectomy, anterior segment reconstruction, membrane dissection, trabeculectomy, lens extraction, vitrectomy, and multiple surgeries, have been reported, but with unsatisfactory outcome [5,6,7].

According to a previous study [8], CFPMSG can be classified into three types based on UBM images: types I, II, and III, with gradual progression of severity. As demonstrated in our previous study [9], anterior segment reconstruction (ASR) is a feasible initial surgical treatment for most CFPMSG, especially type I, which can achieve a stable IOP in early stage patients with long-term follow-up. However, most patients with type II and III glaucoma require a secondary glaucoma surgery.

Anterior segment reconstruction (ASR) is a feasible initial surgical treatment for most CFPMSG cases. However, even though the anterior chamber was formed and deepened, most late-stage patients required secondary glaucoma surgery due to uncontrolled IOP. This study aimed to summarize the clinical outcomes of Ahmed glaucoma valve (AGV) implantation for CFPMSG in patients with uncontrolled IOP after ASR.

Methods

Patients

This was an retrospective study of all children with CFPMSG observed at the Zhongshan Ophthalmic Center, Sun Yat-sen University, between January 2014 and October 2023. The inclusion criteria were as follows: (1) age < 16 years, (2) definite diagnosis of CFPMSG, (3) deepened and stable anterior chamber after ASR, but IOP > 21 mmHg with glaucoma drugs; and (4) follow-up for at least 12 months after AGV. The exclusion criteria were as follows: (1) patients diagnosed with other types of glaucoma and (2) patients who could not tolerate anesthesia owing to systemic conditions. Demographic data, including sex, eye laterality, and age at glaucoma onset, were collected. After surgery, we checked the patients on the day after surgery, and per week in the first month, per month in the following two months, and every 3 months after 6 months post operatively. Final follow-up (FFU) was defined as the last follow-up visit available to patients. This study was reviewed and approved by the Zhongshan Ophthalmic Center Institutional Review and Ethics Board (2020KYPJ121). The study is performed in accordance with the principles of the Declaration of Helsinki. All parents provided informed consent to participate.

Ophthalmic Examination

Consent was obtained for further examination and subsequent surgical intervention. Comprehensive examinations were performed under topical and general anesthesia, including handheld slit-lamp biomicroscopy (Keeler, Bucks, England), slit-lamp photography (BX900; Haag-Streit AG, Koniz, Switzerland), anterior chamber configuration using UBM (50 MHz resolution, model SW-3200 L; Tianjin Suowei Electronic Technology Co., Tianjin, China), IOP by rebound tonometry (iCare PRO; iCare Finland Oy, Helsinki, Finland), axial length (AL), and posterior segment of the eye by A- and B-scan ultrasonography (Quantel Medical, CF, France; Nidek US-1800, Japan). Corneal opacity in CFPMSG patients was classified as mild if iris details were clearly visible, moderate if iris details were partially visible, or severe if no iris details were visible. When we use iCare to measure the IOP, we will avoid cloudy areas of the cornea to eliminate the measurement error.

Ultrasound biomicroscopy

All patients underwent UBM evaluation before and after surgery. The UBM examination procedures were the same as those described in our previous study [8]. The perpendicular distance from the corneal endothelium to the anterior lens surface was defined as the anterior chamber depth (ACD).

Ahmed glaucoma valve implant

The procedures were as follow: (1) 6 − 0 nylon suture was inserted into the superotemporal or inferotemporal limbal cornea; (2) after subconjunctival injection of 0.04 mg/0.1 ml Mitomycin-C(MMC), a fornix-based conjunctival flap was created in the superotemporal or inferotemporal quadrant by blunt dissection until 10 mm from the limbus; (3) the AGV (FP-7/8, New World Medical, Inc., Rancho Cucamonga, CA) implant was primed with BSS; (4) using 8 − 0 silk sutures, the AGV plate was anchored to the superficial sclera 8–9 mm from the limbus between the superior/inferior rectus and lateral rectus muscle; (5) a 5 × 5 mm scleral flap was made 1/2 depth of the sclera 1 mm from the limbus and a 2 × 1 mm scleral tunnel was made posterior from the flap; (6) through a limbal paracentesis, viscoelastic as injected into the anterior chamber to maintain ACD; (7) a bent 23-gauge needle was used to tunnel forward and entered the AC under the flap; (8) passing through the scleral tunnel, the tube was trimmed to the appropriate length and inserted bevel-up into the AC, permitting 2–3 mm insertion in the AC; (9) the tube was placed parallel to the iris plane, with the bevel facing away from the cornea and iris; (10) the tube was sutured to the deep scleral layer and covered by the scleral flap with 10 − 0 nylon sutures; (11) the conjunctiva and Tenon’s capsule was pulled over the plate and sutured at the limbus with 8 − 0 absorbable sutures. (12) At the conclusion of the case, all patients received steroid and antibiotic injections. Postoperatively, tobramycin and dexamethasone drops were prescribed 4 times a day and ointment once before sleep for 1 month. The AGV implantation was performed by a single surgeon (XL) after general anesthesia.

Success criteria

Surgery was considered a complete success when IOP was controlled to ≤ 21 mmHg without glaucoma medication. Qualified success was defined as IOP ≤ 21 mmHg with glaucoma medications. Failure was defined as IOP > 21 mmHg with maximum medications, requirement of an additional operation to lower IOP, and occurrence of severe complications, such as corneal decompensation, severe hyphema, retinal detachment, or endophthalmitis.

Statistical analysis

SPSS (version 22.0, Inc., Chicago, IL, USA) software was used for statistical analysis. Descriptive statistics are presented as means and standard deviations (SD), medians and ranges, or numbers and percentages, as appropriate. The normality of the continuous variable distribution was examined using the Kolmogorov-Smirnov test. For comparison between postoperative and preoperative parameters, Student’s paired t-test or Kruskal-Wallis H test was used, as appropriate. Statistical significance was set at p < 0.05.

Results

Baseline characteristics

Twelve eyes of 12 patients (seven girls and five boys) were included in the study, involving 7 girls and 5 boys. All patients had unilateral CFPMSG, with eight in the right eye and four in the left eye. The patients had an median age of 0.3 (range 0–8) months at onset, and no family history of pupillary abnormalities or glaucoma was recorded. The patients underwent AGV implantation at median age of 11.0 (range 4.5–46) months old and were followed up for 32.0 ± 16.0 months (range 12–58) after AGV implantation. The mean time interval between AGV implant and ASR was 10.0 ± 11.4 months (range 4–37).

Clinical outcomes.

Preoperative and postoperative clinical data, including IOP, medication numbers, and success rates of the enrolled patients, are summarized in Table 1. Of these 12 patients, the classification based on UBM image is as follows: 3 are classified as Type I, 7 are Type II, and 2 are Type III.

Table 1 Preoperative and postoperative comparisons in CFPMSG patients

Before AGV implant, the mean IOP was 29.0 ± 4.0 (range 22–35) mmHg and ACD was 3.21 ± 0.70 mm. After AGV implant, the mean IOP decreased to 18.7 ± 4.5 (range 15–31, p < 0.001) mmHg using less drugs (median:1.5; range 0–3; p < 0.001). The ACD remained almost the same (3.40 ± 0.82 mm, p = 0.57), and tubes were in good position at FFU. One patient developed hyphema after surgery, which resolved within one week. The anterior chamber of another patient became shallow one week after AGV implantation and recovered after three days using atropine ointment. No severe tube-related complications were observed in this study. Figure 1 shows the changes in IOP in the patients before and after AGV implantation during follow-up. The complete success rate for AGV implants was 25% (3/12) and the qualified success rate was 58.3% (7/12). The total success rate was 83.8%.

Fig. 1

Intraocular pressure of patients before and after AGV implantation. Data are presented as the mean ± standard error of the mean. Numbers of patients in each time point were n = 12(before surgery), n = 9(1w), n = 9(1 m), n = 9(3 m), n = 9(6 m), n = 9(9 m), n = 12(12 m), n = 7(1.5y), n = 8(2y), n = 6(2.5y), n = 5(3y) IOP, intraocular pressure; AGV, Ahmed glaucoma valve

Two cases were considered to be failures. One patient had uncontrolled IOP (31 mmHg) at the FFU (58 months) and underwent ciliary photocoagulation as an additional surgery. The IOP was 22.4 mmHg with three types of glaucoma drugs 1.5 years after ciliary photocoagulation. The other case with increased IOP (21.7 mmHg) under 3 kinds of drugs at FFU (50 months) is still being followed up. None of the eyes developed corneal decompensation, RD or endophthalmitis.

Figure 2 shows photographs and UBM images of a representative case from pre-operation to follow-up after AGV implantation. A 3-month-old boy (Patient No.4) was found with corneal opacity in his right eye. His right eye presented with corneal edema, iris stretching to the fibrotic membrane, and severe circumferential iris bombé with anterior synechiae. Pre-operative IOP was 37.2 mmHg and ACD were 1.04 mm. After ASR, the ACD recovered to 2.86 mm and the IOP was normal; however, his anterior chamber angle remained closed. Thirty months later, his IOP increased to 22 mmHg, and the AL increased abnormally, even with the three glaucoma drugs. Hence, AGV implantation was performed, and his IOP was 17.5 mmHg with one type of glaucoma drug at the final 32-months follow-up, with stable ACD and a relatively clear visual axis.

Fig. 2

Representative anterior segment photographs and UBM images of the CFPMSG before ASR (A, B), after ASR (C, D) and after AGV implant (E, F). This is a 3 months old boy who diagnosis with type II CFPMSG. He underwent ASR as initial surgery at 3 moths old and maitained controlled IOP until 30 months later. Then, he received AGV implant for secondary surgery and maitained deep ACD and controlled IOP under 1 glaucoma drops. UBM, ultrasound biomicroscopy; CFPMSG, congenital fibrovascular pupillary membrane-induced secondary glaucoma; ASR, anterior segment reconstruction; AGV, Ahmed glaucoma valve

Discussion

This study indicates that, even though the anterior chamber was deepened and stable after the initial ASR, some CFPMSG patients required secondary glaucoma surgery due to uncontrolled IOP with drugs. Therefore, an additional AGV implant could be an effective and safe option management for them.

Owing to the diversity and complexity of CFPMSG [10,11,12], the outcomes of reported surgical procedures remain controversial. Some surgeons choose to combine ASR with trabeculectomy, trabeculotomy, or others as the initial approach [4, 13]. For instance, in Dr. Liang’s case series [4], one patient (case 1) received ASR combined with lensectomy, trabeculectomy, and anterior vitrectomy as initial treatment, but still suffered from uncontrolled IOP after secondary cyclocryotherapy. Ren et al. study [14] used the term “anterior-anterior type of persistent fetal vasculature (AAPFV)” to describe patients with CFPM, although, 6/11 patients in their cohort presented with manifestations of traditional (anterior type of persistent fetal vasculature) APFV or (posterior type of persistent fetal vasculature) PPFV. They performed dissection of the synechia, pupil formation with lensectomy if combined with cataract (10/11), and vitrectomy when combined with APFV (6/11). Two eyes developed surgical complications, including retinal detachment and hyphema. Three eyes experienced high IOP after the initial surgery, which was managed with glaucoma medication (2/11) or glaucoma surgery (1/11). However, details of the UBM of all enrolled patients were not available. The lack of UBM imaging reports, detailed descriptions of AC conditions, and surgical techniques in previous cases limit our understanding of how to achieve better outcomes.

Our previous studies [9] also indicated that, for some patients with severe CFPMSG, secondary glaucoma surgery is often necessary because of the malfunction of the anterior chamber angle, leading to uncontrolled IOP and the growth of the AL even with maximum glaucoma eye drops. Although the IOP could not be controlled by initial ASR, they achieved a stable anterior chamber because ASR could simplify the procedures in the AC and avoid structural damage of the anterior segment, allowing patients to maintain a quiet and deepened anterior chamber with a relatively clear cornea for a period of time after surgery. This can facilitate further glaucoma procedures if required.

In this study, our results also proved the efficacy and safety of AGV implants for CFPMSG after initial ASR with uncontrolled IOP. Trabeculotomy is not recommended because of closure of the anterior chamber angle and the possibility of recurrence of the fibrovascular membrane [13, 15]. Trabeculectomy is challenging to manage postoperatively in children [16] and has a lower success rate due to the increased risk of scarring in children. In previous studies, cyclocryotherapy or cyclophotocoagulation was used as a secondary surgery for patients with CFPMSG, but the outcome was unsatisfactory due to uncontrolled IOP or even phthisis bulbi [4, 17]. Combined surgery with the use of endodiathermy or bipolar radiofrequency diathermy to cut the membrane carries the risk of lens capsule breakage, inflammation, and destructive structural changes in the anterior chamber [12, 18]. As previously reported, AGV implants have been shown to be effective for refractory glaucoma, including secondary pediatric glaucoma, with a moderate proportion of patients [19,20,21,22] achieving long-term IOP control. In our study, although AGV implantation was relatively challenging, it was efficient and safe, with a complete success rate of 25% and a qualified success rate of 58.3% at a least 12-months follow-up. Three-fourths of our patients were followed up for more than two years, with the longest follow-up being nearly five years. There were two failed cases presenting with uncontrolled IOP, one of which was treated with three glaucoma drugs, and the other one underwent ciliary photocoagulation as an additional surgery. The clinical outcomes were comparable to those of other studies that have used this technique [19, 21].

This study has several limitations, including missing pre- and postoperative data, especially the endothelial cell density (ECD) due to noncompliance, a small sample size for statistical analysis due to the rarity of the condition, and biases inherent in the retrospective study design. In addition, we did not have Perkins tonometry which was more reliable, so we used Icare instead. Future studies should consider incorporating ECD measurements to better assess the long-term effects on corneal endothelium after AGV implation.

Conclusions

In conclusion, these data demonstrate the efficacy and safety of AGV for CFPMSG after ASR, with a stable anterior chamber and uncontrolled IOP. This also suggests that initial ASR and secondary AGV implants could be potential treatment options for CFPMSG.