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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 112  |  Issue : 1  |  Page : 9-13

Effect of Ex-PRESS glaucoma filtration device on corneal endothelium in primary open-angle glaucoma


Department of Ophthalmology, Faculty of Medicine, Mansoura University, Mansoura, Egypt

Date of Submission21-Dec-2018
Date of Acceptance10-Jan-2019
Date of Web Publication26-Apr-2019

Correspondence Address:
Sherif El-Saeed El-Kholy
Ophthalmology Center, Faculty of Medicine, Mansoura University, Mansoura 35516
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_69_18

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  Abstract 

Purpose The aim of this study is to compare the effect of Ex-PRESS minishunt versus standard trabeculectomy on corneal endothelial cell count (ECC) in cases of primary open-angle glaucoma.
Setting This comparative prospective nonrandomized study was conducted at Mansoura Ophthalmic Center, Mansoura University, Mansoura, Egypt.
Patients and methods The study included 36 eyes of 25 patients with uncontrolled primary open-angle glaucoma. Nineteen eyes had Ex-PRESS glaucoma minishunt and 17 eyes had trabeculectomy. Specular microscopy was used to measure ECC using TOMEY EM-3000. ECC was measured preoperatively and compared with postoperative values at 6 and 12 months.
Results The mean endothelial cell density was 2493.2±246.8 cells/mm2 before the surgery in the Ex-PRESS group and 2473.8±259.8 cells/mm2 in the trabeculectomy group (P=0.82). This value decreased significantly in both groups at 12 months postoperatively to 2348.1±309.5 in the Ex-PRESS group and 2276.1±342.4 in the trabeculectomy group. ECC loss at 1 year was less in the Ex-PRESS group at 5.7 versus 8% in the trabeculectomy group (P=0.051).
Conclusion Ex-PRESS minishunt is considered a safe procedure regarding corneal endothelium, showing less decrease in ECC than conventional trabeculectomy.

Keywords: Ex-PRESS, glaucoma, intraocular pressure, trabeculectomy


How to cite this article:
El Rehim DA, El-Hessy AAA, El-Saeed El-Kholy S, Nematalla EH, El-Saeed EM. Effect of Ex-PRESS glaucoma filtration device on corneal endothelium in primary open-angle glaucoma. J Egypt Ophthalmol Soc 2019;112:9-13

How to cite this URL:
El Rehim DA, El-Hessy AAA, El-Saeed El-Kholy S, Nematalla EH, El-Saeed EM. Effect of Ex-PRESS glaucoma filtration device on corneal endothelium in primary open-angle glaucoma. J Egypt Ophthalmol Soc [serial online] 2019 [cited 2019 Jun 26];112:9-13. Available from: http://www.jeos.eg.net/text.asp?2019/112/1/9/257216


  Introduction Top


Glaucoma is considered the most common cause of irreversible blindness in the world. In 2013, the number of patients with glaucoma worldwide was estimated to be 64.3 million and may reach 76 million in 2020, and this number may increase more to 111.8 million in 2040 [1]. Trabeculectomy is the main surgical procedure in managing patients with uncontrolled glaucoma. However, it may cause various complications such as hypotony, choroidal detachment, hyphema, malignant glaucoma, and infection [2]. To improve the outcomes, many modifications have been developed, such as using anti-metabolites. Ex-PRESS minishunt for standard fistulization is one of the alternatives [3].

The EX-PRESS glaucoma filtration device (Alcon Laboratories) is nonvalved minishunt. It is made of medical-grade stainless steel. It got the US Food and Drug Administration approval in 2002. Using this minishunt, the aqueous humor is diverted from the anterior chamber to a created intrascleral space [4]. Its length is 2.64 mm and has two different internal lumen sizes, either a 50 or 200 μm. In the original procedure, the Ex-PRESS was implanted directly under the conjunctiva. This old procedure had many complications such as extrusion, hypotony, conjunctival erosion, and others. Implantation under scleral flap started in 2005 [5].

In young adults, the corneal endothelial cell count (ECC) is approximately 3000 cells/mm2. This value decreases annually (0.5±0.6% every year) owing to aging. This loss can be increased in patients with glaucoma because of different risk factors such as argon laser iridotomy, surgery, and even glaucoma itself [6].

Glaucoma filtration surgery either conventional trabeculectomy or glaucoma drainage implant can cause corneal endothelial cell loss after the surgery [7]. Ahmed glaucoma valve, as it has long tube in the anterior chamber, leads to more loss in the corneal ECC than conventional trabeculectomy [8].

There are different hypotheses explaining ECC loss following glaucoma surgeries, especially regarding devices. Some of these may be inflammation in the anterior chamber, device corneal touch, changes in the composition of the aqueous humor, low preoperative endothelial cell density (ECD) [9], peripheral anterior synechiae, or combination of these factors [10].

The purpose of this study was to evaluate the safety of the Ex-PRESS mini glaucoma shunt on the corneal endothelium in comparison with the conventional trabeculectomy.


  Patients and methods Top


This was a comparative, prospective, nonrandomized study. The study protocol has been approved from medical research ethics committee, faculty of medicine, Mansoura University. It was performed in Mansoura Ophthalmic Center, Faculty of Medicine, Mansoura University, Egypt. Thirty-six eyes of 25 patients were included in the study. Seventeen eyes underwent subscleral trabeculectomy (group 1) and 19 eyes underwent Ex-PRESS (Alcon Laboratories. Fort Worth, Texas, USA) P 50 minishunt implantation (group 2). The study was carried out through 24 months in the period from November 2015 to November 2017.

Inclusion and exclusion criteria

The study included patients above the age of 18 years diagnosed as having primary open-angle glaucoma [by intraocular pressure (IOP) measurement, gonioscopy, optic nerve evaluation, and visual field assessment], with one of the following indications of surgery:
  1. Failure to control IOP in spite of maximum medical or laser therapy.
  2. Noncompliance with medications owing to financial or physical restrictions.
  3. Need to achieve lower target IOP in the presence of progressive optic nerve and visual field loss.
  4. Intolerance to medical therapy secondary to allergies.
  5. Advanced glaucomatous optic neuropathy.


In this study, we excluded patients with other types of glaucoma such as uveitic, pseudoexfoliation, pigmentary, and pseudophakic glaucoma. Moreover, patients with previous ocular surgery or trauma and patients with ocular diseases were excluded.

Endothelial cell count evaluation

Specular microscopy with a noncontact-type specular microscope (Tomey EM-3000, Nishi-ku, Nagoya, Japan) was performed before and 6 and 12 months after the surgery. All examinations were carried out on the central cornea. Several images were taken, and the image with the best clarity was used for the quantitative analyses.

Other documented parameters

Demographic data were recorded. Complete ophthalmic evaluation was done for all patients, including best-corrected visual acuity, slit-lamp biomicroscopy, gonioscopy, Goldmann applanation tonometry, and dilated fundus examination. Success rate, complications, and number of glaucoma medications were recorded postoperatively.

A written consent from all patients was taken after being informed of the risks, benefits, and alternatives of surgery.

Surgical technique

Following corneal traction suture with vicryl 7/0, a fornix-based conjunctival peritomy was done, and then a large 5×5 mm scleral flap with depth of approximately 50% was fashioned then dissection up to clear cornea. For entering the anterior chamber, a 25 G needle supplied by the manufacturer was used. The site of entry was in the center of the blue–gray transition zone just anterior to scleral spur. Holding the needle during entry had to be parallel to the iris plane toward the center of the pupil for proper positioning of the device. Before entering with the needle, release of traction helps to allow the eye to return to primary position and holding the scleral flap in a manner that allows visualization of the needle as it fully enters the anterior chamber.

Viscoelastic material was used to partially fill the anterior chamber. The implant was then inserted through the perforation site using its special injector, first the posterior slit opening of the device parallel to the limbus and then dialing it 90° to its final position perpendicular to the limbus. The scleral flap was then sutured securely using 5 10/0 nylon sutures to properly cover the flange of the implant. Finally, the conjunctiva was sutured with 2 10–0 nylon sutures.

Postoperatively, all eyes received the same medications, where topical steroid/antibiotic combination (dexamethasone/tobramycin) eye drops and ointment were used. Dose of drops was four times daily in the first week with gradual tapering along the following 4–6 weeks.

Statistical analysis

IBM’s statistical package for the social sciences statistics for Windows (version 24) was used for statistical analysis of the collected data. Shapiro–Wilk test was used to check the normality of the data distribution. Normally distributed continuous variables were expressed as mean±SD whereas categorical variables and the abnormally distributed continuous ones were expressed as number and percentage or median and interquartile range, respectively. Intergroup comparisons were conducted using Student’s t test and Mann–Whitney for normally and abnormally distributed continuous data, respectively, whereas intragroup comparisons were conducted using related samples Wilcoxon’s signed rank test (for nonparametric data) or paired Student t test (for parametric data). P value less than 0.05 was considered statistically significant.


  Results Top


Comparison between both groups revealed statistically insignificant difference regarding demographic and clinical data. Age range was 51.12±13.38 years in group 1 and 51.32±12.28 years in group 2 (P=0.963). Group 1 included 13 (76.5%) males and four (23.5%) females, and group 2 included 16 (84.2%) male and three (15.8%) female. Follow-up period was 15 months in group 1 and 13 months in group 2 (P=0.34). Both groups had similar glaucoma severity before operation in terms of mean cup-disc ratio and visual field mean deviation ([Table 1]).
Table 1 Demographic and clinical data of both groups

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The mean ECD was 2493.2±246.8 cells/mm2 before the surgery in the Ex-PRESS group and 2473.8±259.8 cells/mm2 in the trabeculectomy group (P=0.82). This value decreased significantly in both groups at 12 months postoperatively to 2348.1±309.5 in the Ex-PRESS group and 2276.1±342.4 in the trabeculectomy group. ECC loss at 1 year was less in the Ex-PRESS group at 5.7 versus 8% in the trabeculectomy group (P=0.051) ([Table 2], [Figure 1] and [Figure 2]).
Table 2 Preoperative and postoperative endothelial cell count

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Figure 1 Graph shows endothelial cell count preoperatively and 6 and 12 months postoperatively.

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Figure 2 Endothelial cell count distribution in both groups at 12 months.

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Complications encountered in this study were recorded. Early hypotony was slightly higher in trabeculectomy (29.4%) than Ex-PRESS (10.5%) but not statistically significant (P=0.153). Moreover, shallow anterior chamber was higher in trabeculectomy group at 23.5% versus 10.5% in the Ex-PRESS (P=0.296). Although these complications were transient and improved with conservative treatment, they may have an effect on corneal ECC.


  Discussion Top


Recently, as alternatives to standard trabeculectomy, many new IOP-lowering procedures have been developed. One of them is the Ex-PRESS minishunt, which is a new procedure for standardizing trabeculectomy. Advantages of using Ex-PRESS may include absence of sclerotomy and iridectomy and less anterior chamber inflammation [2]. In this study, the ECC loss at 1 year following Ex-PRESS was less than trabeculectomy (5.7 vs. 8%), though not significant statistically (P=0.051).

Similar to the results in this study, Omatsu and colleagues compared Ex-PRESS with trabeculectomy regarding the effect on ECC, and they concluded that Ex-PRESS device implantation appears to be a safer procedure with less endothelial cell loss. The mean ECC in the trabeculectomy group was 2505±280 cells/mm2 at baseline, whereas it was 2349±323 cells/mm2 (P<0.001) and 2277±385 cells/mm2 (P=0.003) at 12 and 24 months, respectively. However, the ECC in the Ex-PRESS group was 2377±389 cells/mm2 at baseline, and reduced to 2292±452 cells/mm2 (P=0.043) and 2317±449 cells/mm2 (P=0.274) at 12 and 24 months, respectively [7]. Moreover, Wagschal et al. [11] reported the corneal endothelial cells (CEC) loss by 3.5% at 1 year following Ex-PRESS device.

In the study by Omatsu et al. [7], the loss of ECC after Ex-PRESS was 5.0% at 1 year and 9.4% at 2 years. The change between the baseline and 1 year was not statistically significant (P=0.39); however, the change between the baseline and 2 years (P<0.001) and between 1 and 2 years (P=0.001) were both statistically significant [7]. Ishida et al. [12] reported that the ECD decreased significantly from 2529±327 cells/mm2 preoperatively to 2471±356 cells/mm2 (2.2%) at 1 year and to 2428±315 cells/mm2 (4.0%) at 2 years after the Ex-PRESS implantation.Lee et al. [13] also reported ECC loss higher in trabeculectomy group at 18.2±13.3% (P=0.021) compared with 10.0±7.0% (P=0.139) in the Ex-PRESS group.

Casini and colleagues compared ECC loss following trabeculectomy, Ex-PRESS implantation, and Ahmed glaucoma valve implantation for 3 months after surgery. They reported that the corneal endothelium (CE) did not change significantly after Ex-PRESS either at 1 month (0.2% decrease) or at 3 months (0.3% decrease), whereas trabeculectomy and Ahmed glaucoma valve implantation resulted in a significant loss of corneal ECD [14].

Against the previous results, the study by Arimura and colleagues noticed more reduction of corneal ECD after Ex-PRESS than after trabeculectomy. They explained this by possibility of damage caused by foreign body reaction or immune reactions cause by stainless material of the tube, turbulence of aqueous humor around the inner tip of the tube, or mechanical contact between the corneal endothelium and the tube [15].

In conclusion, Ex-PRESS minishunt is considered a safe procedure regarding corneal endothelium, showing less decrease in ECC than conventional trabeculectomy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Tham Y-C et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. Ophthalmology 2014; 121:2081–2090.  Back to cited text no. 1
    
2.
Wang W et al. Ex-PRESS implantation versus trabeculectomy in Chinese patients with POAG: fellow eye pilot study. Int J Ophthalmol 2017; 10:56.  Back to cited text no. 2
    
3.
Bhatt A et al. Comparison of Baerveldt 101-350 glaucoma implant (BGI) versus trabeculectomy with ExPress™ shunt for the treatment of primary open angle glaucoma. Vision 2017; 1:15.  Back to cited text no. 3
    
4.
Shaarawy T, Goldberg I, Fechtner R. EX-PRESS glaucoma filtration device: review of clinical experience and comparison with trabeculectomy. Surv Ophthalmol 2015; 60:327–345.  Back to cited text no. 4
    
5.
Salim S. Ex-PRESS glaucoma filtration device—surgical technique and outcomes. Int Ophthalmol Clin 2011; 51:83–94.  Back to cited text no. 5
    
6.
Gagnon M-M et al. Corneal endothelial cell density in glaucoma. Cornea 1997; 16:314–318.  Back to cited text no. 6
    
7.
Omatsu S et al. Changes in corneal endothelial cells after trabeculectomy and EX-PRESS shunt: 2-year follow-up. BMC Ophthalmol 2018; 18:243.  Back to cited text no. 7
    
8.
Koo EB et al. Effect of glaucoma tube shunt parameters on cornea endothelial cells in patients with Ahmed valve implants. Cornea 2015; 34:37–41.  Back to cited text no. 8
    
9.
Kim CS et al. Changes in corneal endothelial cell density and morphology after Ahmed glaucoma valve implantation during the first year of follow up. Clin Exp Ophthalmol 2008; 36:142–147.  Back to cited text no. 9
    
10.
Hau S et al. Corneal endothelial morphology in eyes implanted with anterior chamber aqueous shunts. Cornea 2011; 30:50–55.  Back to cited text no. 10
    
11.
Wagschal LD et al. Prospective randomized study comparing Ex-PRESS to trabeculectomy: 1-year results. J Glaucoma 2015; 24:624–629.  Back to cited text no. 11
    
12.
Ishida K et al. Effect of glaucoma implant surgery on intraocular pressure reduction, flare count, anterior chamber depth, and corneal endothelium in primary open-angle glaucoma. Jpn J Ophthalmol 2017; 61:334–346.  Back to cited text no. 12
    
13.
Lee GY et al. Long-term efficacy and safety of ExPress implantation for treatment of open angle glaucoma. Int J Ophthalmol 2017; 10:1379.  Back to cited text no. 13
    
14.
Casini G et al. Trabeculectomy versus EX-PRESS shunt versus Ahmed valve implant: short-term effects on corneal endothelial cells. Am J Ophthalmol 2015; 160:1185–1190.  Back to cited text no. 14
    
15.
Arimura S et al. Randomised clinical trial for postoperative complications after Ex-PRESS implantation versus trabeculectomy with 2-year follow-up. Sci Rep 2018; 8:16168.  Back to cited text no. 15
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

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