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 Table of Contents  
Year : 2022  |  Volume : 2  |  Issue : 2  |  Page : 416-418

Pars plana relocation of existing glaucoma implant for tube exposure and corneal endothelial decompensation

1 Glaucoma Service, Prabha Eye Clinic and Research Centre, Bengaluru, Karnataka, India
2 Vitreoretinal Service, Prabha Eye Clinic and Research Centre, Bengaluru, Karnataka, India

Date of Submission24-Aug-2021
Date of Acceptance16-Dec-2021
Date of Web Publication13-Apr-2022

Correspondence Address:
Gowri J Murthy
Prabha Eye Clinic and Research Centre, 504, 40th cross, Jayanagar 8th Block, Bengaluru - 560 070, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijo.IJO_2183_21

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Glaucoma implant tube exposure and corneal endothelial decompensation are complications of implant surgeries in eyes with glaucoma. We describe a surgical method of managing these complications by relocation of the existing anterior chamber implant tube into the pars plana, after a three-port pars plana vitrectomy. We studied eight eyes of eight patients, four with perilimbal tube exposure and four with endothelial decompensation, who underwent the procedure. Four eyes of the four patients had resolution of tube exposure without recurrence and maintained stable intraocular pressure (IOP); visual acuity and IOP remained stable in the endothelial decompensation group.

Keywords: Ahmed Glaucoma Implant, Aurolab aqueous drainage implant, endothelial decompensation, tube exposure, tube repositioning

How to cite this article:
Murthy GJ, Murthy PR, Gowda SM, Prabhakar SP, Hiremath MR. Pars plana relocation of existing glaucoma implant for tube exposure and corneal endothelial decompensation. Indian J Ophthalmol Case Rep 2022;2:416-8

How to cite this URL:
Murthy GJ, Murthy PR, Gowda SM, Prabhakar SP, Hiremath MR. Pars plana relocation of existing glaucoma implant for tube exposure and corneal endothelial decompensation. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2023 Jun 9];2:416-8. Available from: https://www.ijoreports.in/text.asp?2022/2/2/416/342934

Glaucoma drainage devices are invaluable in the surgical management of refractory glaucomas. However, implants are also associated with sight-threatening complications.

The incidence of complications like tube exposure is 2.5%–8.9% in the first 5 years post-surgery.[1],[2] Management includes conjunctival repair, conjunctival or scleral grafts, and tube relocation.[3]

Corneal endothelial decompensation is another complication with a cumulative risk of up to 3.3%, 5 years post-surgery.[4] Management includes procedures to relieve the endothelial touch using sutures or valve explantation. Definitive management needs a total corneal or endothelial graft.

The management of the complications is not only challenging, but also associated with low success rates and a possible recurrence. We propose a novel method of surgical management for these two complications, whereby the existing tube is explanted from the anterior chamber and reinserted into the pars plana.

  Case Reports Top

This is a retrospective interventional case series done in a tertiary care hospital in Bangalore. The study included four eyes of four patients with tube exposure (anterior/perilimbal within 2.5 mm) and four eyes of four patients with corneal endothelial decompensation. Six patients had a standard AhmedTM Glaucoma Valve Model FP7 and two patients had Aravind aqueous drainage implant (AADI). Institutional ethics committee approval and patient consents were obtained prior to the surgical procedure.

Surgical Technique

A limited conjunctival peritomy was performed over the tube area. One of the superior pars plana ports was placed in line with the tube, 3.5 mm from the limbus, with the entry angled straight toward the center of the eye. A thorough 23G vitrectomy was done, with care taken to excise the vitreous base. After completion, the pars plana cannula near the tube was removed. The implant tube was removed from the anterior chamber, and without trimming, it was inserted into the pars p lana cannula entry site. The angled entry of the 23G cannula done earlier ensured that the tube enters at an obtuse angle to the globe wall and does not kink. The tube was anchored to the scleral with a 7-0 vicryl suture. Mattress sutures were applied to the prior corneal entry site using 10-0 nylon and secured with an additional scleral patch graft. Other ports and conjunctiva were closed.

For the eye with tube exposure, the outcome variables were resolution of exposure, pre-operative and post-operative comparison of intraocular pressure (IOP) and antiglaucoma (AGM) usage pre-operative vs post-operative.

In endothelial decompensation eyes, since endothelial counts were already very low, we used maintenance in best corrected visual acuity (BCVA) as a surrogate outcome measure. Pachymetry readings were not available.

The demographic details and pre-implant diagnosis are given in [Table 1].
Table 1: Details of eyes with tube exposure and corneal endothelial decompensation

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Seven eyes underwent pars plana relocation of the tube combined with a pars plana vitrectomy, and Patient 4 underwent tube relocation alone as it was a previously vitrectomized eye.

Tube Exposure Group

All four eyes had resolution of tube exposure with no recurrence or complications during the follow-up period (1.5 months–5 years). [Table 2] shows the comparison of IOP and the use of AGM and BCVA. [Figure 1] shows preoperative and post-operative photos of patient 2.
Figure 1: Top: Preoperative photographs of Patient 2, with perilimbal exposure and Seidel test. Bottom: Postoperative photographs of Patient 2 after tube relocation into pars plana

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Table 2: Postoperative outcomes of relocation for tube exposure and corneal endothelial decompensation

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Endothelial Decompensation Group

All four eyes maintained IOP with no change in the number of AGM post-relocation. All eyes showed either an initial improvement or maintained BCVA [Table 2] and [Figure 2]. Patient 2 and Patient 3 initially showed improvement in BCVA, but later the condition deteriorated due to progression of diabetic retinopathy and myopic posterior pole degeneration, respectively.
Figure 2: Top: Preoperative photographs of Patient 5 showing tube cornea touch. Bottom: Postoperative photographs of Patient 5 after relocation into pars plana

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  Discussion Top

Tube exposure is a sight-threatening complication following implant surgery, predisposing to endophthalmitis.[5] The conventional management involving additional grafting has variable success rate with a possible re-exposure.[6]

The commonest site of exposure is near the limbus. Scarred conjunctiva following repeated surgeries and constant rubbing of lid margins against the conjunctiva overlying the tube act as contributing factors.[7],[8] Shifting the tube entry into the pars plana avoids the limbal area with thin overlying tenons and conjunctiva. There is lesser friction due to blinking and lesser conjunctival dissection compared to performing tube implantation at a new site.

Another advantage with our technique is most eyes with an implant are for uncontrolled secondary glaucomas, which may have invariably undergone or require vitrectomy for retinal conditions.

We did not use pars plana clip to change the direction of the tube. Aqueous egress through tube is not compromised as long as the entry is not acute angled. This is evidenced by the fact that IOP was maintained with no need for further AGM in all cases.

Corneal decompensation due to loss of endothelial cells is a well-documented complication of glaucoma implants.[4] The main aim is to reposition the tube away from the endothelium to prevent further damage. In our series, we opted to reposition the tubes into the pars plana as a first step. If need be, a possible corneal graft may be done later.

Patient 1 and Patient 4 have maintained vision with topical hypertonic saline and are on wait list for corneal graft. Patient 2 and Patient 3 have chosen not to undergo corneal grafting due to the poor prognosis associated with their retinal pathologies. In our patients, a subsequent graft has not yet been performed; however, the procedure may be needed for eyes with significant corneal edema.

Advantage of pars plana tube placement is that air bubble placement following a Descemet's membrane endothelial keratoplasty (DMEK) can be done without compromising the tube drainage.

Good IOP control was observed following our intervention without the need for further AGM, indicating no alteration in the functioning of the tube following relocation.

Main limitation of the study is the small sample size. However, we have followed up the patients fairly for a long term. In the event of a retinal break during our method, the use of tamponading agents like gas or silicone oil may compromise the functioning of the implant, thereby posing a potential limitation. We have fortunately not encountered this in our series.

  Conclusion Top

Pars plana relocation of an existing glaucoma implant tube with a vitrectomy is a relatively simple and effective management for complications like tube exposure and endothelial decompensation.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Wishart PK, Choudhary A, Wong D. Ahmed glaucoma valves in refractory glaucoma: A 7-year audit. Br J Ophthalmol 2010;94:1174-9.  Back to cited text no. 1
Netland P, Chaku M, Ishida K, Rhee D. Risk factors for tube exposure as a late complication of glaucoma drainage implant surgery. Clin Ophthalmol 2016;10:547-53.  Back to cited text no. 2
Alawi A, AlBeshri A, Schargel K, Ahmad K, Malik R. Tube revision outcomes for exposure with different repair techniques. Clin Ophthalmol 2020;14:3001-8.  Back to cited text no. 3
Kim KN, Lee SB, Lee YH, Lee JJ, Lim HB, Kim CS. Changes in corneal endothelial cell density and the cumulative risk of corneal decompensation after Ahmed glaucoma valve implantation. Br J Ophthalmol 2016;100:933-8.  Back to cited text no. 4
Al-Torbak AA, Al-Shahwan S, Al-Jadaan I, Al-Hommadi A, Edward DP. Endophthalmitis associated with the Ahmed glaucoma valve implant. Br J Ophthalmol 2005;89:454-8.  Back to cited text no. 5
Oana S, Vila J. Tube exposure repair. J Curr Glaucoma Pract 2012;6:139-42.  Back to cited text no. 6
Lankaranian D, Reis R, Henderer JD, Choe S, Moster MR. Comparison of single thickness and double thickness processed pericardium patch graft in glaucoma drainage device surgery: A single surgeon comparison of outcome. J Glaucoma 2008;17:48-51.  Back to cited text no. 7
Minckler DS, Francis BA, Hodapp EA, Jampel HD, Lin SC, Samples JR, et al. Aqueous shunts in glaucoma: A report by the American Academy of Ophthalmology. Ophthalmology 2008;115:1089-98.  Back to cited text no. 8


  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


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