Cauterized suture for complete tube occlusion of Ahmed glaucoma valve in hypotony maculopathy

Introduction

Historically, hypotony maculopathy (HM) is an uncommon condition typically characterized by low intraocular pressure (IOP), associated with reduced central vision, triggering optic nerve swelling, and folding of the retina and/or choroid^1,2 or other structural changes. ³ HM incidence increased to 20% after the introduction of glaucoma-filtering surgery,^4,5 and it is known that (1) male sex, (2) myopia, (3) primary filtering surgery with an antifibrotic agent, and (4) young age (less than 60 years) are all risk factors associated with this condition. ⁶ Early detection and resolution of HM is essential since permanent chorioretinal changes and poor visual outcome can occur without treatment.

The use of glaucoma drainage devices (GDD) is becoming more frequent in the treatment of both refractory glaucoma and in first filtration procedures and leads to some common, but benign conjunctival complications. ⁷ Nevertheless, HM is a serious clinical problem that may present after GDD implantation. Ahmed glaucoma valve (AGV) (New World Medical, Inc., Rancho Cucamonga, LA, USA) has been shown to lower the incidence of postoperative hypotony than non-valved GDD^8–10 However, HM occurs despite valve design or fluid flow optimization^11,12 and its management is difficult because it does not completely resolve (IOP increase is enough to reverse the structural alterations) with medical treatments.^8,13,14 In addition, it has been reported that cyclophotocoagulation could lead to ciliary body inhibition, generating an additional hypotony added to the AGV overfiltration itself. ¹

This article presents our experience treating HM with a simple, minimally invasive, and removable ab interno tube AGV occlusion.

Methods

The surgery can be performed under topical anesthesia. A paracentesis was created at limbus 90 degrees away from the tube followed by viscoelastic (Hyaluronic acid; 10 mg/mL; Biolon^®, Tedec-Meiji Farma) injection into the anterior chamber. A 5–0 polypropylene suture (Prolene; Ethicon) was inserted into the AGV tube via a second paracentesis site created in the same meridian of the GDD. The length of the tube was measured, and an external suture cauterization was performed after trimming it to allow an easier and safer fixation in the tube, thus totally occluding the lumen. The suture was introduced into the tube itself with the viscoelastic 27-gauge cannula until the occlusion of the tube was concluded. VisionBlue (0.006% version of Trypan blue, DORC, Zuidland, The Netherlands) was used to visualize flow through the tube, thus being sure that it was totally occluded (see video as supplementary online material). In case of necessity, the suture could be removed with a 23G Grieshaber Revolution^® DSP (Alcon) vitreoretinal instrument.

The procedures adhered to the tenets of the Declaration of Helsinki, and patients signed a consent form for scientific purposes.

Results

This technique was performed in three cases of HM with a complex history of medical treatments.

Case 3

A 49-year-old man consulted due to progressive visual loss after a cyclophotocoagulation 2 weeks before. BCVA was 0.04 Snellen. His ocular history revealed a keratoplasty and posterior AGV insertion. Fundus examination and optical coherence tomography (OCT) showed retinal folds (Figure 1, left). Increased choroidal thickness was detected by echography. Tube occlusion with suture insertion was done, under topical anesthesia, without complications intra- or postoperatively. Maculopathy was resolved in a month and corroborated with OCT images (Figure 1, right). No reliable IOP measurements were taken pre- and post-suture insertion due to cornea condition.

OPEN IN VIEWER

Figure 1.

Retinal folds of case three (49-year-old male): (left) preoperative OCT image and (right) postoperative OCT image at 1 month after Ahmed glaucoma valve tube occlusion.

Conclusion

Tube occlusion with polypropylene had been first proposed in Baerveldt GDD to maintain anterior chamber during phacoemulsification ¹³ and was systematically applied during Baerveldt GDD implantation with variable results after removing the occlusion. ¹⁵

Other alternatives like tube or complete GDD removal to reverse hypotony may cause conjunctival and scleral damage due to the invasive nature of the intervention, ¹⁶ and the patient may again need additional medication and surgery to control IOP. Tube ligation is another alternative to reverse hypotony, but it has shown to have a relatively high rate of failure. Stein et al. ⁸ found a rate of failure in the procedure that varied according to the suture material used from 20% to 50% including primary and secondary revisions. These failures required additional surgery.

Comparing with the other alternatives discussed earlier, the surgical technique presented here is more easily removable under topical anesthesia; it does not require special materials, results in no damage to the conjunctiva, and thus allows future glaucoma surgery alternatives if needed. In addition, a resorbable suture could be used as an alternative to prevent removal maneuvers, albeit noted that this is not exempt from certain complications.

Nevertheless, the set of three complex cases described in this study is not large enough to comprehensively assess the beneficial effects of this procedure, warranting a larger clinical study with more patients.

In conclusion, intraluminal AGV occlusion with cauterized suture is a simple, relatively quick, reversible, and effective technique that may offer a minimally invasive way to resolve HM in complex cases and avoid severe loss of vision.