Outcomes of Ahmed glaucoma valve implantation in pediatric glaucoma

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BACKGROUND

Pediatric glaucoma is a known heterogeneous group of diseases with the potential to cause blindness, and most of them are refractory to drug therapy. It includes primary congenital glaucoma, glaucoma associated with systemic congenital diseases and anomalies of eyeball development (such as Sturge–Weber syndrome, Peters anomaly, and aniridia), and secondary glaucoma (such as uveal, steroid-induced glaucoma, glaucoma associated with retinopathy of prematurity, and aphakic and neovascular glaucoma [1–3]. Childhood glaucoma, considering its resistance to surgical and medical treatment, can be classified as refractory glaucoma [2, 4, 5]; however, more refractory forms of glaucoma can be distinguished within this refractivity.

Goniotomy and trabeculotomy are the surgeries of choice in the treatment of patients with primary congenital glaucoma. If “angular surgery” is ineffective, the surgeon proceeds to the next stages of surgical treatment, i.e., trabeculectomy and implantation of drainage devices [2–6]. As for the other types of pediatric glaucoma, no surgical algorithm has been established for many of them, and in such situations, the implantation of drainage devices often becomes the first antihypertensive surgery.

The anti-glaucoma drainage made by Antony Molteno was first implanted in a child in 1973 [7]. Since then, many studies have investigated the efficiency and complication rates of these interventions in pediatric patients [2–4, 8–16]. The drainage system Ahmed Glaucoma Valve (New World Medical, Inc., Rancho Cucamonga, CA, USA) became the most accessible for pediatric ophthalmologists. Thus, it is relevant to evaluate the efficiency of the implantation of this device in various forms of pediatric glaucoma.

The work aimed to evaluate the efficacy of Ahmed Glaucoma Valve drainage implantation in pediatric patients with refractory glaucoma.

MATERIALS AND METHODS

The results of the surgical treatment of 52 children (67 eyes), who underwent implantation of the Ahmed valve for refractory glaucoma in the Ophthalmology Department of St. Petersburg State Pediatric Medical University from 2011 to 2020, were evaluated.

All pediatric patients, depending on the form of glaucoma, were distributed into three groups, namely, primary congenital glaucoma (n = 8, 11 eyes); glaucoma associated with a congenital malformation of the eyeball (n = 17, 23 eyes), including aniridia syndrome (n = 8, 13 eyes), microspherophakia (n = 3, 4 eyes), Sturge–Weber syndrome (n = 1; 1 eye), Axenfeld–Rieger syndrome (n = 1; 1 eye), Peters anomaly (n = 1; 1 eye), and anterior segment dysgenesis with sclerocornea (n = 3; 3 eyes); and secondary glaucoma (n = 27, 33 eyes), including aphakic glaucoma (n = 10, 12 eyes), glaucoma due to retinopathy of prematurity (n = 7; 8 eyes), uveal glaucoma (n = 5; 8 eyes), glaucoma due to silicone tamponade (n = 1; 1 eye), glaucoma associated with familial exudative vitreoretinopathy (n = 1; 1 eye), and traumatic glaucoma (n = 3; 3 eyes).

Ophthalmological examination before and after surgery included visometry with maximum correction (if possible due to the child’s age), biomicroscopy, gonioscopy, goniography, indirect ophthalmoscopy, tonometry (according to Maklakov, and in case of unfeasibility, with an ICare tonometer), keratometry, and ultrasonography in A and B modes. If necessary, studies, especially in young children, were performed under drug-induced sleep using sevoflurane.

Patients were followed up every 3 months within a year after surgery and then every 6 months. Instillations of topical antihypertensive drugs were added as needed to achieve the target intraocular pressure (IOP) (P_o > 22 mm Hg, without an increase in the anteroposterior segment [APS]).

Surgical efficiency throughout the follow-up period was recorded when stable ophthalmotonus (P_o) was achieved (IOP = 6–22 mm Hg), in the absence of complications potentially leading to loss of visual functions (valve tube erosion, retinal detachment, hemorrhagic ciliochoroidal detachment, and endophthalmitis), and in the absence of the need for repeated hypotensive surgeries. Cases when revision and needling of the valve platform were required for encapsulation of the filtration bleb were not classified as having poor outcomes if the tube position remained stable and the IOP was compensated. In situations when valve replacement was required because of its dislocation or inefficiency, as well as implantation of a second drainage device, only the results of the first implantation were included in the study, and this case was also classified as a poor outcome.

The surgical technique in pediatric patients was standard and almost did not differ from the surgery in adult patients; however, some anatomical aspects of the children’s eyeball were considered. The valve platform was always sutured to the sclera 8 mm aside from the limbus to reduce fibrous changes in Tenon’s capsule. The length of the intraocular part of the tube was not less than 2 mm owing to the risk of its retraction with an increase in the size of the eyeball APS. In eyes with buphthalmos, a 25 G puncture was performed to avoid filtration of the intraocular fluid around the tube and to minimize postoperative hypotension. The outer part of the tube was covered with an alloplant graft to prevent tube erosion and development of infectious complications [2, 8–10]. In case of small sizes of the orbit, a canthotomy was performed for the correct position of the valve platform in two cases. The tube was inserted into the anterior chamber parallel to the iris surface in 64 eyes, to the ciliary sulcus in three eyes, and through the flat part of the ciliary body in two eyes.

The minimum follow-up period was 6 months, while 29 pediatric patients were followed up for more than 5 years (Table 1).

 

Table 1. Number of patients followed-up after valve implantation / Таблица 1. Количество пациентов, наблюдавшихся после имплантации клапана

Follow-up period, months	0	6	12	24	36	48	60	72	84
Number of patients	67	65	59	56	46	39	29	29	28

 

RESULTS

The study included 52 pediatric patients (67 eyes; 19 girls and 33 boys) aged 1 month to 17 years old. The children were examined before and after surgery (Table 2).

 

Table 2. Characteristics of examined patients / Таблица 2. Характеристика обследованных пациентов

Parameters	Total	Disease etiology
		primary congenital glaucoma	glaucoma associated with congenital anomalies	secondary glaucoma
Number of patients (eyes)	52 (67)	8 (11)	17 (23)	27 (33)
Boys: number of patients (eyes)	33 (41)	8 (11)	11 (13)	14 (17)
Girls: number of patients (eyes)	19 (26)	0	6 (10)	13 (16)
Age at implantation (range)	6.6 ± 0.6 (1 month to 17 years)	4.5 ± 1.2 (9 months to 14 years)	4.9 ± 1.2 (1 month to 16 years)	8.3 ± 0.8 (9 months to 17 years)
Average follow-up period (range), months	44.0 ± 4.9 (6–120)	59.5 ± 10.2 (30–90)	26.0 ± 6.3 (6–114)	51.7 ± 7.4 (6–120)
Average intraocular pressure (Ро) before surgery, mm Hg	32.1 ± 0.6	31.4 ± 1.3	32.5 ± 0.9	31.9 ± 0.9
Average intraocular pressure (Ро) at the last examination, mm Hg	18.5 ± 0.4	19.75 ± 0.9	17.1 ± 0.5	19.1 ± 0.5
Average anteroposterior eyeball size before surgery, mm	25.0 ± 0.3	27.8 ± 0.5	23.9 ± 0.6	24.9 ± 0.4
Average anteroposterior eyeball size at the last examination, mm	24.2 ± 0.6	28.0 ± 0.7	23.3 ± 0.6	23.9 ± 0.9
Previous hypotensive surgeries:	1.7 ± 0.2	2.9 ± 0.4	0.9 ± 0.3	1.8± 0.3
·                trabeculectomy	1.37 ± 1.0	2.36 ± 0.5	0.7 ± 0.9	1.3 ± 0.9
·                cyclophotocoagulation	0.7 ± 0.8	0.5 ± 0.6	0.42 ± 0.6	1.05 ± 1.0

 

The age of the patients at the time of surgery was 6.6 ± 0.6 years (1 month to 17 years), whereas pediatric patients in the group with secondary glaucoma were older (t = 2.36; p < 0.05). The mean follow-up period after valve implantation was 44.0 ± 4.9 (6–120) months. The mean IOP range before surgery was 21–42 mm Hg, and it was 12–22 mm Hg at the end of the follow-up (t = 18.8; p < 0.01). The IOP values before and after surgery were comparable in all three groups (t = 0.7–0.3, p > 0.05). The average anteroposterior size of the eyeball exceeded the age norm, at 25.0 ± 0.3 mm (19.0–29.97 mm) before surgery and did not change significantly after surgery (24.2 ± 0.6 mm), and the differences were not significant (t = 1.2, p > 0.05). In patients with congenital glaucoma, the eyeball size was larger than that in other groups (t = 4.9–4.5, p < 0.01).

In 67.2% of the cases, other anti-glaucoma surgeries were performed before implantation of the Ahmed valve (average 1.7 ± 0.2 surgeries per child). Half of the patients (35 of 67 eyes, 52.2%) underwent at least one filter-type surgery (sinus trabeculectomy). In 25 of 67 eyes (37.3%), cyclodestructive surgeries were performed before valve implantation. No patients had received implantation of drainage devices previously. The smallest number of hypotensive surgical interventions before valve implantation was performed in patients with glaucoma that developed in presence of congenital syndromes (39.1% of eyes, an average of 0.9 surgeries in each child), and the differences with other groups were significant (t = 4.1–2.2, p < 0.05). In 16 pediatric patients (22 eyes), Ahmed valve implantation was the first hypotensive surgery. These were patients with glaucoma, in which trabeculectomy is usually ineffective, associated with aniridia syndrome (n = 7, 11 eyes) (Fig. 1–3), with aphakic glaucoma (n = 4, 5 eyes), with anterior eye dysgenesis with sclerocornea (n = 3, 3 eyes), with glaucoma associated with familial hereditary exudative vitreoretinopathy (n = 1, 1 eye), and uveal glaucoma (n = 1, 2 eyes).

 

Fig. 1. The eye of a newborn child with glaucoma due to congenital aniridia / Рис. 1. Глаз новорождённого ребёнка с глаукомой на фоне врождённой аниридии

 

Fig. 2. The eye of a 16-year-old child with aniridic syndrome / Рис. 2. Глаз ребёнка 16 лет с аниридийным синдромом

 

Fig. 3. The eye of a 14-year-old child with aniridic syndrome, pseudophakia with an implanted valve / Рис. 3. Глаз ребёнка 14 лет с аниридийным синдромом, артифакией с имплантированным клапаном

 

According to our data, the hypotensive effect of the surgery persists for 6 months in 97% of the patients, which subsequently decreases [4, 10–14, 16]. Thus, the surgery efficiency was 91.8%, 82%, and 73.9% after 1, 2, and 3 years, respectively, and reached 42.8% after 7 years of follow-up (Fig. 4).

 

Fig. 4. Dynamics of the hypotensive effect of Ahmed valve implantation during the follow-up period / Рис. 4. Динамика гипотензивного эффекта операции имплантации клапана Ахмеда за период наблюдения

 

A comparative analysis of Ahmed valve implantation efficiency in pediatric patients was performed based on the literature data (Table 3).

 

Table 3. Comparative results of Ahmed valve implantation in pediatric glaucoma / Таблица 3. Сравнительные результаты имплантации клапана Ахмеда при детской глаукоме

Author	Number of patients (eyes)	Mean age (years)	Previous surgery, %	Follow-up period, months	Preservation of the hypotensive effect for 1–5 years, %
					1	2	3	4	5
O. Albis-Donado (2010) [11]	106 (128)	7.58	32.8	25.7	82	79	70	41	–
F. Al Mobarak (2009) [13]	36 (42)	0.98	100	24	74	63	–	–	–
Y. Ou (2009) [14]	19 (30)	1.8	93	57.6	63	50	50	41	33
H.K. Yang (2008) [17]	29 (34)	5.5	44.1	–	69	46	–	–	–
Y. Morad (2003) [3]	44 (60)	6	97	24.3	93	86	71	45	–
S. Balekudaru (2014) [18]	71 (71)	6.8	67	37.8	97	80	–	–	–
R. Autratta (2007) [19]	76 (76)	6.9	55.2	85.2	91	82	76	71	67
A. Chen (2015) [20]	100 (136)	7.1	30	75.6	88	–	–	–	55
K. Spiess (2021) [21]	23 (29)	2	–	85.4	68	64		54	54
M. Pakravan (2018) [16]	72 (95)	7.9	–	51.3	81	72	66	62	59
Study presented	52 (67)	6.6	67.2	44.0	92	82	74	67	55

 

No intraoperative complications occurred during valve implantation. Postoperative complications included the following:

• Encapsulation of the filtering bleb in 17 eyes (25.3%) (Fig. 5). In all cases, the valve platform was revised, a portion of the capsule above it was excised, while the tube position remained stable, and IOP was compensated after surgery.
• Retraction of the iris to the tube, with a change in the pupil shape in three eyes (4.5%) (Fig. 6).
• Retraction of the tube in one eye (1.5%), namely, displacement of the tube end to the limbus zone due to eyeball stretching. The valve platform was displaced anteriorly (Fig. 7).
• Ciliochoroidal detachment (Fig. 8) in the early postoperative period in three eyes (4.5%), which was stopped using conservative therapy with corticosteroids; one case required posterior scleral trepanation.
• Complicated cataract in 2 (3.0%) eyes associated with buphthalmos. Planned phacoaspiration was performed.

 

Fig. 5. Bleb encapsulation / Рис. 5. Инкапсуляция фильтрационной подушки

 

Fig. 6. Retraction of the iris to the tube (shown by the arrow) / Рис. 6. Ретракция радужки к трубке (показана стрелкой)

 

Fig. 7. Tube retraction / Рис. 7. Ретракция трубки

 

Fig. 8. Echogram of a patient with postoperative total ciliochoroidal detachment / Рис. 8. Эхограмма пациента с послеоперационной тотальной цилиохориоидальной отслойкой

 

Tube erosion was registered in 3 (4.5%) eyes. In one case (1.5%), this led to the development of endophthalmitis in a child who, 3 months after surgery, had acute conjunctivitis associated with chickenpox (Fig. 9). In other cases, the tube was additionally covered with alloplant, and the platform position remained stable throughout the follow-up. Retinal detachment was detected in 4 (6.0%) eyes. In all cases, it was diagnosed in the late postoperative period (i.e., after 6 months or longer) in eyes with buphthalmos, and its relationship with valve implantation was not significant.

 

Fig. 9. The eye of a 5-year-old patient with endophthalmitis due to tube erosion 3 months after implantation of the Ahmed valve / Рис. 9. Глаз пациента 5 лет с эндофтальмитом, возникшим вследствие эрозии трубки через 3 мес. после имплантации клапана Ахмеда

 

The amount and nature of complications of drainage device implantation in pediatric patients differ significantly in various literature sources. For example, their frequency ranged from 84.6% in the study by Chen et al. [12] (44/52 eyes) up to 28.9% according to Albis-Donado et al. [11]. Table 4 presents the comparison of the incidence of complications in our study and literature [2, 3, 4, 11–16].

 

Table 4. Postoperative complications of Ahmed valve implantation / Таблица 4. Послеоперационные осложнения имплантации клапана Ахмеда

Type of complication	Literature data, %	Study presented, %
Anterior displacement of the tube with its contact with the cornea	2–34	–
Tube retraction	3.9–8.3	1.5
Conjunctival erosion with tube eruption	1.6–7	4.6
Endophthalmitis	Single cases	2.3
Obstruction of the drainage tube by blood, fibrin, lens capsule, or vitreous body	4–13.5	–
Retraction of the iris to the tube, resulting in a change in the pupil shape	До 21	9.3
Bleb encapsulation	21–30	32.5
Mobility disorders, diplopia, and gaze limitation	1.9–7.3	–
Hypotension with Po <5 5 mm Hg	10–42	–
Ciliochoroidal detachment	2.1–4.2	6.8
Retinal detachment	2.2–7.1	9.3
Hemophthalmos	3.9–8	–
Cataract	Single cases	2.3
Hyphema	Single cases	–
Valve platform displacement	Single cases	2.3

 

We also analyzed risk factors for adverse outcomes after Ahmed valve implantation in pediatric patients (Table 5). Significant factors were an increase in the eyeball APS by ≥20% compared with the age norm, the IOP at the time of surgery was >32 mm Hg, and there was a history of anti-glaucoma-filtering surgeries.

 

Table 5. Risk factors for unfavorable outcome after Ahmed valve implantation / Таблица 5. Факторы риска развития неблагоприятного исхода после имплантации клапана Ахмеда

Risk factor	Х2	p
Age <1 year	0.01	>0.05
Anteroposterior segment exceeding the age norm by 20%	7.9	<0.05
Age <5 years	1.4	>0.05
Intraocular pressure >32 mm Hg	20.1	<0.05
Previous antihypertensive filter-type surgeries	7.8	<0.05
Previous non-glaucomatous surgeries	0.02	>0.05
Previous cyclodestructive surgeries	0.9	>0.05

 

CONCLUSION

The Ahmed Glaucoma Valve drainage device can be implanted in refractory pediatric glaucoma if previous surgeries were ineffective. In some cases, namely, with buphthalmos, aphakic, avitreal eyes, dysgenesis of the anterior segment of the eye with underdevelopment of the anterior chamber angle, this intervention is the only possible means of reducing IOP and preserving visual functions and the eyeball. In such cases, this intervention is advisable as the first surgery.

The decrease in the efficiency of the drainage device over time should be considered, as well as the possibility of complications in the late postoperative period; thus, long-term case follow-up of these patients is necessary.

ADDITIONAL INFORMATION

Author contributions: All authors confirm that their authorship complies with the ICMJE criteria. All authors have made significant contributions to the development of the concept, research and preparation of the article, read and approved the final version before its publication.

Funding: The study had no external funding.

Conflict of interest: The authors declare no conflict of interest.

Informed consent to publication: The authors obtained the written consent of the patient’s legal representatives for the publication of medical data and photographs.

About the authors

Natalia N. Sadovnikova

St. Petersburg State Pediatric Medical University

Email: natasha.sadov@mail.ru
ORCID iD: 0000-0002-8217-4594

Cand. Sci. (Med.), Head of Department of Ophthalmology

Russian Federation, 2, Litovsckaya st., Saint Petersburg, 194100

Vladimir V. Brzheskiy

St. Petersburg State Pediatric Medical University

Email: vvbrzh@yandex.ru
ORCID iD: 0000-0001-7361-0270

Dr. Sci. (Med.), Head of Department of Ophthalmology

Russian Federation, 2, Litovsckaya st., Saint Petersburg, 194100

Natalia V. Prisich

St. Petersburg State Pediatric Medical University

Email: prisichnv@rambler.ru
ORCID iD: 0000-0001-7749-7850

Ophthalmologist

Russian Federation, 2, Litovsckaya st., Saint Petersburg, 194100

Marina A. Zertsalova

St. Petersburg State Pediatric Medical University

Email: mazercalova@mail.ru
ORCID iD: 0000-0003-4559-0051

Assistant of Department of Ophthalmology

Russian Federation, 2, Litovsckaya st., Saint Petersburg, 194100

Andrei Yu. Baranov

St. Petersburg State Pediatric Medical University

Author for correspondence.
Email: homeandrey@rambler.ru
ORCID iD: 0000-0002-6024-4635

Assistant of Department of Ophthalmology

Russian Federation, 2, Litovsckaya st., Saint Petersburg, 194100

References

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