Comparative evaluation of the results of surgical treatment of open-angle glaucoma using an Ex-Press® P-200 filtration device and drainage device “anti-glaucoma implant A3”

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INTRODUCTION

Glaucoma still is one of the leading causes of irreversible vision loss worldwide [8]. Herewith, the share of primary open-angle glaucoma (POAG) is about 75% of cases [9]. As of 2015, the number of people suffering from this form of the disease reached about 58 million, with expected increase up to 65 million people by 2020, and up to 111 million by 2040 [10]. About 8.4 million people are bilaterally blind because of glaucoma [11].

Over the last years, in open-angle glaucoma (OAG) treatment, medical IOP-lowering therapy and different varieties of laser surgery got great development. Currently, a specific group of glaucoma procedures is highlighted – Minimally Invasive Glaucoma Surgery (MIGS).

Nevertheless, classic trabeculectomy and its multiple modifications still are the procedures of choice for moderate and advanced disease stages. This group of surgeries is designated as filtration surgeries, and aims to create additional aqueous humor (AH) outflow pathways, predominantly under the conjunctiva. With that, a so-called filtration bleb forms.

Unfortunately, it is not always possible to achieve a long-lasting optimal IOP-lowering effect after surgery. According to the data from different authors, a decrease of the IOP-lowering effect after filtration surgery is observed in 15–45% of cases [1] reaching up to 37–70% of cases [2]. The main cause of a recurrent intraocular pressure (IOP) rise is a development of proliferative process leading to the scarring of new aqueous humor outflow pathways. The severity of the proliferative process is directly correlated to the intensity of exudative and inflammatory manifestations arising in response to surgical trauma [3].

The filtration bleb scarring is a terminal stage of an aseptic inflammatory process, arising in affected tissues of the eye after surgery. On the average, scar reorganization begins in 10–14 days postoperatively, and ends to the 21 day [4].

In view of this, an important objective in glaucoma surgery is a slowdown of the regeneration process – to preserve the permeability of formed aqueous humor outflow pathways. For this purpose, in global ophthalmic practice, several methods are used to suspend ocular tissue regeneration in the operation area, and this is performed according to two main focus areas: therapeutic action on reparation processes in the scarring area (use of cytostatics, e.g. anti-metabolite 5-fluorouracil [5]), and use of drainage devices (implants, shunts, valves) [6].

Concerning the first area, the off-label use of anti-metabolites and cytostatics (widely used abroad in filtration surgical procedures) is not allowed in the Russian Federation.

Over the course of glaucoma surgery development, many authors proposed different variants of devices implanted into the anterior chamber and aiming to enhance the aqueous humor outflow. In foreign countries, a widespread use gained the implantation of a filtering device Ex-Press^® (Excessive Pressure Regulating Shunt System), manufactured in several modifications and believed to be an alternative to traditional trabeculectomy. In our country, Ex-Press^® filtration device did not get any wide use due to its relatively high cost.

However there is an alternative variant of the tube shunt – Russian-made “Anti-glaucoma implant A3” produced by OOO “Reper NN” (Nizhny Novgorod). According to design and to internal lumen diameter this device is similar to the P-200 model of filtration device Ex-Press^®.

In present article, we present a comparative evaluation of surgical treatment results of OAG patients using Ex-Press^® P-200 filtration device and drainage device “Anti-glaucoma implant A3”.

MATERIALS AND METHODS

52 patients (59 eyes) with different OAG stages were included into the study. They were divided into 2 groups using simple sequential sampling. Into the group I, 28 patients (32 eyes) were included, in whom Ex-Press^® P-200 filtration device was implanted. Group II consisted of 24 patients (27 eyes). They were subjects to surgery with “Antiglaucoma implant A3” implantation.

The diagnosis was established on the basis of history data and objective instrumental examination results.

Standard ophthalmic examination included automatic refractometry, visual acuity testing, biomicroscopy of the anterior segment, gonioscopy of the irido-corneal angle, indirect ophthalmoscopy.

For objective assessment of glaucoma stabilization, in all patients, we performed static (threshold) automated perimetry using Pericom perimeter, and optical coherence tomography (OCT) (Heidelberg Spectralis HRA-OCT) of the optic nerve heads to measure the thickness of the nerve fiber layer.

For IOP measurement, the ICare TA01i non-contact tonometer was used, having a high degree of result correlation with Goldman tonometer, which is an international clinical standard of intraocular pressure measurement.

Ex-Press^® filtration device is used from 2002 on. It represents a tube of medical stainless steel with 200 micron internal lumen diameter and 2.64 mm length. On the sharpened distal end, there is an additional port and a “beard” to fix the shunt in the anterior chamber. On the other end, there is a plate for fixation on the scleral bed. The device implantation is not a contraindication for magnetic resonance imaging.

Drainage device “Anti-glaucoma implant A3” in current modification is used from 2014 on. As described above, the device is produced in Nizhny Novgorod at the enterprise OOO “Reper NN”. The device was designed by Tambov branch of S. Fyodorov Eye Microsurgery Federal State Institution and the Ophthalmology Chair of the Privolzhsky Research Medical University. It represents a tube shunt from transparent acrylic polymer with square cross section, and has a 3.2 mm length. The shunt’s distal end is cut at an angle of 45° and has an auxiliary port of 0.1 mm diameter. On the proximal end, there is a support element for implant’s fixation under a scleral flap (Tabl. 1).

Techniques of surgical procedures using these types of filtration devices do not differ significantly from each other. Implantation was performed in upper parts of the eye on 12 hours or in areas free of previous procedures. After dissection of the conjunctiva and excision of the Tenon’s capsule, a superficial limbal-based scleral flap is formed up to so-called grey zone. Meridianal intrascleral canal is formed in intermediate scleral layers, which reached beyond the superficial flap. A paracentesis is done using 22G or 23G needle for “Anti-glaucoma implant A3” and Ex-Press^® P-200, respectively. Filtration device Ex-Press^® P-200 is implanted with disposable injector enclosed. The drainage of the Reper Company is positioned with special reusable forceps, jaws of which have notches repeating the form of the device’s supporting element [7].

The evaluation of surgical procedure results was done at discharge from the hospital, it is, on the 3^rd–5^th day after surgery, and further on every 6 months, with maximal follow-up of more than three years.

 

Table 1 / Таблица 1

Comparison of the main technical characteristics of Ex-Press^® P-200 shunt devices and drainage “Anti-glaucoma implant A3”

Сопоставление основных технических характеристик шунтирующих устройств Ex-Press^® P-200 и «Имплантат антиглаукомный А3»

Technical characteristics	Ex-Press® P-200 (Alcon, USA)	Anti-glaucoma implant A3 (OOO “Reper-NN”, Russia)
Material	Stainless medical steel	Hydrophobic acryl
Length	2.64 mm	3.20 mm
Cross section	Round, diameter 400 microns	Square, side length 400 microns
Lumen diameter	200 microns	200 microns
End bevel	45°	45°
Additional port	Present	Present, 100 microns
Fixation furrow	Present	Present
Fixation spur	Present	Not present
Installational features	Paracentesis with 22G needle. Implantation with an injector	Paracentesis with 23G needle. Implantation with a forceps

 

RESULTS

Despite the undertaken IOP-lowering therapy, at the time of admission, the average intraocular pressure’s level was above the normal level in both groups, and was 26.87 ± 6.11 and 25.85 ± 7.75 mm Hg, respectively. 17 (53.12%) of patients from the group I and 20 (74.07%) patients from the group II were had a maximum regimen of instillations (3 medications). In 20 (62.5%) patients from the group I and 18 (66.67%) patients from the group II, IOP-lowering procedures had been carried out, which did neither lead to glaucomatous process stabilization, nor to “target” pressure achievement.

The dynamic follow-up of the IOP level in the early post-op period showed that after 3–5 days after surgery in the group I in 27 (84.38%) patients, hypotony was present, normal IOP was found in 4 (12.5%) cases, and in one patient (3,13%), in the early post-op period, ophthalmic hypertension was revealed. In the group II, low IOP was found in 25 (92.59%) eyes, and normal IOP level in 2 (7.41%) cases. There were no ophthalmic hypertension cases.

6 months after surgery, in the group I in 26 (81.25%) patients out of 32 the IOP was normalized without any IOP-lowering medication. In 6 (18.75%) cases, the target IOP level was reached using one medication. In the group II, 20 (74.07%) patients did not need any IOP-lowering therapy, as target IOP level was reached. In 7 (25.93%) cases, to normalize the IOP level one medication was prescribed.

In one after surgery, in the group II, 15 (57.69%) patients did not need any therapy. In 8 (30.77%) cases, IOP was stabilized by instillation of 1 medication. To reach the target level, for 2 (7.69%) patients, two medications were prescribed. In 1 case (3.85%), IOP was normalized at a maximal instillation regimen (3 medications). In 1 case (3.85%), a diode-laser transscleral cyclocoagulation (TSCPC) was performed. In the group II, in 11 cases (44.0%), pressure was stabilized without drops, for 11 (44.0%) patients 1 IOP-lowering medication was prescribed, for 2 (8%) – 2 preparations to stabilize the IOP level were given, and 1 patient (4.0%) received 3 medications. In 1 case (4.0%), a diode-laser TSCPC was performed.

In 1.5 years after surgery, in the group I, in 5 patients (25.0%), a stable IOP normalization was preserved. In 13 cases (65.0%), one medication was prescribed. In 2 patients (10.0%), the IOP level was stabilized using two medications. In the group II, 8 patients (33.33%) stayed without any therapy. In 10 cases (41.67%), to stabilize the IOP level, one medication was prescribed. In 6 eyes (25.0%), the target IOP level was reached using two medications. In 1 case (4.17%), to stabilize intraocular pressure figures, a diode-laser TSCPC was performed.

In 2 years after the implantation of drainage devices, in the group I, pressure stayed normal without IOP-lowering medications in 3 cases (16.67%). One medication was prescribed in 12 cases (66.66%), 2 preparations – in 3 cases (16.67%). In 2 cases (11.11%), a diode-laser TSCPC was performed. In the group II, in 6 cases (26.09%), the IOP level stayed in the limits of target figures without prescription of IOP-lowering medications. One medication was prescribed to 11 patients (47.82%), in 6 cases (26.09%), – two medications. A diode-laser TSCPC to stabilize the IOP level was performed in one patient (4.34%).

After 2.5 years of follow-up, in group I, in 4 people (33.33%), IOP stayed normal without instillations of IOP-lowering medications. The target IOP level was reached with one medication in 4 cases (33.33%). 4 patients (33.33%) were in need of three medications. In the group II, 2 patients (14.28%) preserved stabilized IOP without therapy. In 4 cases (28.57%), to maintain target IOP, one medication was prescribed, in 6 (42.87%) – two, and in 2 cases (14.28%) – 3 medications. In two patients of the group, to stabilize IOP, a diode-laser TSCPC was performed.

In 3 years after surgery, in group I, 1 patient (14.28%) did not instill any IOP-lowering medication to maintain target IOP level. Two and three medications were prescribed to 3 (42.86%) and 3 (42.86%) patients, respectively. In the group II, 1 patient (14.28%) preserved the target IOP level without drop instillation. To five patients (71.44%), 2 medications were prescribed, and to one patient (14.28%) – 3 medications (Table. 2).

 

Table 2 / Таблица 2

Mean intraocular pressure values (mm Hg) depending on the follow-up time (M ± SD)

Средние значения внутриглазного давления (мм рт. ст.) в зависимости от срока наблюдения (M ± SD)

Group	Follow-up period
	Before surgery	3–5 days	6 months	1 year	1.5 years	2 years	2.5 years	3 years
Group I	26.87 ± 6.11	5.39 ± 2.91	12.68 ± 2.61	14.16 ± 2.57	13.97 ± 2.21	13.83 ± 1.6	15.00 ± 3.33	13.46 ± 2.21
Group II	25.85 ± 7.75	4.30 ± 2.88	13.11 ± 3.5	13.04 ± 4.34	13.00 ± 2.09	12.83 ± 2.42	14.29 ± 4.75	14.43 ± 4.79

 

Table 3 / Таблица 3

Intraocular pressure level depending on follow-up time, n

Зависимость уровня внутриглазного давления от срока наблюдения, n

Follow-up period	Intraocular pressure level (mm Hg)
	2–10		11–20		21–30		≥31
	I	II	I	II	I	II	I	II
At admission	–	–	5	3	20	21	6	3
			16.1%	11.1%	64.5%	77.8%	19.4%	11.1%
3–5 days	30	25	1	2	–	–	–	–
	96.8%	92.6%	3.2%	7.4%	–	–	–	–
6 months	6	7	25	18	0	2	–	–
	19.4%	25.9%	80.6%	66.7%	0.0%	7.4%	–	–
1 year	1	6	30	17	0	2	–	–
	3.2%	22.2%	96.8%	63.0%	0.0%	7.4%	–	–
1.5 years	2	2	28	22	1	0	–	–
	6.5%	7.4%	90.3%	81.5%	3.2%	0.0%	–	–
2 years	1	3	29	20	0	0	–	–
	3.2%	11.1%	93.5%	74.1%	0.0%	0.0%	–	–
2.5 years	0	2	26	10	1	2	–	–
	0.0%	7.4%	83.9%	37.0%	3.2%	7.4%	–	–
3 years	1	1	23	5	0	1	–	–
		3.7%	74.2%	18.5%	0.0%	3.7%	–	–
Note. n – number of patients.

 

Table 4 / Таблица 4

Mean best corrected visual acuity according to follow-up time (M ± SD)

Средняя максимально корригированная острота зрения в зависимости от срока наблюдения (M ± SD)

Group	Follow-up period
	Before surgery	3–5 days	6 months	1 year	1.5 years	2 years	2.5 years	3 years
Group I	0.48 ± 0.29	0.52 ± 0.3	0.5 ± 0.34	0.5 ± 0.35	0.5 ± 0.32	0.41 ± 0.28	0.37 ± 0.29	0.47 ± 0.32
Group II	0.44 ± 0.28	0.44 ± 0.29	0.47 ± 0.3	0.46 ± 0.3	0.43 ± 0.32	0.5 ± 0.37	0.26 ± 0.19	0.35 ± 0.26

 

Table 5 / Таблица 5

Optical coherence tomography data of patients, n

Значения данных оптической когерентной томографии пациентов, n

Follow-up period	Dynamics of the RNFL thickness								Total number of patients
	0 – negative dynamics		1 – no dynamics		2 – positive dynamics		3 – cannot be assessed
	Group I	Group II	Group I	Group II	Group I	Group II	Group I	Group II	Group I	Group II
6 months	–	–	29	23	0	2	3	2	32	27
	–	–	90.6%	85.2%	0.0%	7.4%	9.4%	7.4%	100.0%	100.0%
1 year	1	1	22	22	–	–	3	2	26	25
	3.8%	4.0%	84.6%	88.0%	–	–	11.5%	8.0%	100.0%	100.0%
1.5 years	0	2	19	20	–	–	1	2	20	24
	0.0%	8.3%	95.0%	83.3%	–	–	5.0%	8.3%	100.0%	100.0%
2 years	4	4	14	19	–	–			18	23
	22.2%	17.4%	77.8%	82.6%	–	–			100.0%	100.0%
2.5 years	0	1	11	12	–	–	1	1	12	14
	0.0%	7.1%	91.7%	85.7%	–	–	8.3%	7.1%	100.0%	100.0%
3 years	0	1	8	5	–	–	0	1	8	7
		14.3%	100.0%	71.4%	–	–	0.0%	14.3%	100.0%	100.0%
Note. n – number of patients. RNFL – retinal nerve fiber layer. Dynamics (Friedman’s criterion): for group I p = 0.221; for group II p = 0.543.

 

Table 6 / Таблица 6

Changes in patients’ visual fields by automated perimetry, n

Данные изменения компьютерной периметрии КПЗ пациентов, n

Follow-up period	Dynamics of automated perimetry data						Total number of patients
	0 – negative dynamics		1 – no dynamics		2 – positive dynamics
	I	II	I	II	I	II	I	II
6 months	–	–	32	25	0	2	32	27
	–	–	100.0%	92.6%	0.0%	7.4%	100.0%	100.0%
1 year	1	1	25	24	–	–	26	25
	3.8%	4.0%	96.2%	96.0%	–	–	100.0%	100.0%
1.5 years	0	2	20	22	–	–	20	24
	0.0%	8.3%	100.0%	91.7%	–	–	100.0%	100.0%
2 years	3	3	15	20	–	–	18	23
	16.7%	13.0%	83.3%	87.0%	–	–	100.0%	100.0%
2.5 years	0	2	12	12	–	–	12	14
	0.0%	14.3%	100.0%	85.7%	–	–	100.0%	100.0%
3 years	0	1	8	6	–	–	8	7
	0.0%	14.3%	100.0%	85.7%	–	–	100.0%	100.0%
Note. n – number of patients.

 

Table 7 / Таблица 7

Post-operative complications, n

Осложнения в послеоперационном периоде, n

Group	Post-operative complications								In total
	No complications	Cilio-choroidal detachment	Hyphema	Cataract	Shunt eruption	Corneal dystrophy	Fibrin	Hypotony
Group I	22	1	3	1	2	0	1	2	32
	68.8%	3.1%	9.4%	3.1%	6.3%	0.0%	3.1%	6.3%	100.0%
Group II	18	1	4	3	0	1	0	0	27
	66.7%	3.7%	14.8%	11.1%	0.0%	3.7%	0.0%	0.0%	100.0%
Note. n – number of patients.

 

At the time of admission, mean best corrected visual acuity in the group 1 was 0.48 ± 0.29, and in the second one – 0.44 ± 0.28. Data on visual acuity changes depending on follow-up terms are presented in the Tabl. 4.

CONCLUSIONS

1. Both variants of filtration devices have similar construction and implantation technique.
2. The target IOP level was reached in all patients, but much of them needed an additional prescription of therapy. In the present study with patients’ follow-up, within three years after implantation, there was no statistically significant difference in IOP level revealed.
3. Best corrected visual acuity within the 2 years follow-up time stayed on the level close to the initial one. But in 3 years, visual acuity was just above in patients, to whom filtration device Ex-Press^® Р-200 has been implanted
4. According to the OCT data, negative dynamics was registered only in one patient in the “Implant A3” group after a follow-up of more than two years. According to remaining dynamic indicators, during all the follow-up time, there was no statistically significant difference between groups revealed. A similar pattern was observed in functional visual field testing of patients. Statistically significant differences involved only the follow-up terms of more than two years, and negative dynamics was recorded only in a patient of the group II.

Thus, the clinical efficacy of both devices appeared comparable.

About the authors

Maria K. Grineva

Academican I.P. Pavlov First St. Petersburg State Medical University of the Ministry of Healthcare of the Russian Federation

Author for correspondence.
Email: mariagrineva83@gmail.com
ORCID iD: 0000-0003-1279-7996
SPIN-code: 4547-9835
ResearcherId: D-8824-2019

Postgraduate, Ophthalmology Department

Russian Federation, Saint Petersburg

Sergey Yu. Astakhov

Academican I.P. Pavlov First St. Petersburg State Medical University of the Ministry of Healthcare of the Russian Federation

Email: astakhov73@mail.ru
SPIN-code: 7732-1150
Scopus Author ID: 56660518500

MD, PhD, DMedSc, Professor, Head of the Ophthalmology Department

Russian Federation, Saint Petersburg

Vadim A. Turgel

I.P. Pavlov First St. Petersburg State Medical University

Email: Zanoza194@gmail.com

Resident, Department of Ophthalmology

Russian Federation, Saint Petersburg

References

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