eyeWatch™ System Combined with Non-plated Intraorbital Tube Insertion for the Management of Refractory Glaucoma: A Case Series

INTRODUCTION

The eyeWatch™ system (Rheon Medical, Switzerland)¹ is a novel device designed to control the outflow of aqueous following aqueous shunt procedures. The device includes a rotating magnetic plate, which can compress or decompress a silicone tube thus enabling controlled increase or decrease resistance in aqueous outflow.¹ According to its original concept, the eyeWatch™ device is connected to a non-valved aqueous shunt plate (eyePlate) positioned intraorbitally as a standard seton system and the amount of tube compression can be adjusted both intraoperatively and postoperatively through a purpose-designed magnet.¹ Through the combined function of the eyeWatch™ and a non-valved plate, aqueous outflow can be adjusted so that the conditions, such as postoperative hypotony or hypertony, may be adequately addressed without the need for commonly required measures, such as anti-glaucomatous medications (for the management of hypertony) or, more importantly, ligating or tube-obstructing sutures for the management of hypotony.² However, such a surgical approach includes both the preparation and intraorbital implantation of the non-valved plate as well as the insertion of the eyeWatch™ device, thus increasing the complexity and duration of the procedure.

Taking into account that in such a system the element controlling aqueous outflow is the eyeWatch™ device, the whole procedure could be modified so that the element of non-valved plate (i.e., the direction of the aqueous in the intraorbital space) becomes quicker and easier to perform. Accordingly, we propose a modification of the procedure in which, instead of implanting a non-valved plate, a single perforated tube is inserted into the orbital space through a purpose-designed injector. In this case series, we present results from this approach in three cases as a quicker and less invasive option to the standard eyeWatch™ implantation surgery.

MATERIALS AND METHODS

This study was conducted at the University Hospital of Heraklion, Crete, Greece as part of a multicentric study on the effectiveness of the eyeWatch™ system. The study was in accordance with the Tenets of Helsinki Declaration and informed consent was obtained from all patients before enrollment to the study, following a detailed explanation on the nature, features, and risks of the protocol. Adult patients suffering from primary open angle glaucoma resulting in complete vision loss in the affected eyes (absolute glaucoma) were included. Moreover, all included patients had an elevated IOP of >20 mm Hg under maximally tolerated medications associated with pain in the study eye (blind painful eye) and had previous failed filtering surgery in the study eye. Exclusion criteria were multiple and included neovascular glaucoma, congenital glaucoma, traumatic glaucoma, history of previous intraocular surgery in the study eye referring to extraocular muscles (strabismus), corneal transplant, retinal surgery, aphakia, retinopathy, optic neuropathy other than glaucoma, retinal vein or artery occlusion in the study eye, corneal opacifications or irregularities that may interfere with the optic nerve evaluation or the IOP measurements in the study eye, a history of severe eye trauma in the study eye, microphthalmia in the study eye, concurrent inflammatory/infective eye disorder in the study eye, severe systemic disease or disabling conditions, such as chronic renal failure, post organ transplants as well as pregnancy, breastfeeding, or mental handicap. Overall, three eyes of three patients were included in this series.

A thorough clinical ophthalmic examination was completed in all cases and all examinations were repeated on the 1st postoperative day, the 1st and 2nd postoperative weeks, and the 1st, 3rd, 6th, and 12th postoperative months. On each postoperative interval, the position of the eyeWatch™ tube into the anterior chamber, the integrity of conjunctiva overlying the eyeWatch™ mechanism and covering pericardium, and any aqueous leakage from the incision sites were also examined. The position of the valve in the eyeWatch™ mechanism was checked both at the conclusion of surgeries and on all postoperative intervals. In case the IOP was above 20 mm Hg or under 5 mm Hg, opening or closing (respectively) of the mechanism was attempted as per the manufacturer’s instructions. Moreover, one patient (patient no. 1) underwent a CT scan of the orbits (GE Healthcare, Waukesha, WI, USA) to confirm the position of the eyeWatch™ mechanism and intraorbital tube.

A standard eyeWatch™ system was used in all cases. However, instead of a plated non-valved implant, a silicone tube was connected to the eyeWatch™ implant. The tube, manufactured by Rheon Medical, is a 4 cm-long silicone tube, which features 24 lateral microholes of 40 μm of diameter allowing multiple drainage exit sites for aqueous humor. The tube is provided within its injector, which features a sliding mechanism allowing placement of the tube at the target position chosen by the surgeon (Fig. 1).

All surgeries were performed under topical anesthesia (Ropivacaine Hydrochloride, Naropeine, AstraZeneca, Cambridge, UK), administered by both subconjunctival and sub-Tenon’s injections by the same surgeon (ETD). Following the placement of a corneal traction suture for adequate infraduction of the eyeball, a conjunctival peritomy was performed at the superior–temporal quadrant. Entrance into the anterior chamber was achieved with a 25G needle and a side port was also prepared with 19G blade. The eyeWatch™ mechanism was sutured on the sclera with 8.0 prolene sutures and its tube inserted into the anterior chamber through the prefashioned 25G tract. The retro-orbital space at the ipsilateral (superior–temporal) quadrant was then prepared with blunt dissection at the sub-Tenon’s space. The tube was then inserted into the prepared sub-Tenon’s space of the superior–temporal quadrant using a purpose-designed blunt-ended injector (the product is still investigational), which allows for the release of the tube once the tip of the injector has reached the area of the orbital apex (4 cm). Once the tube was in place, it was released from its injector and the tip of the tube connected to the connector of the eyeWatch™ implant after securing it with transscleral 8.0 nylon suture (Fig. 1). The position of the magnetic disc in the eyeWatch™ mechanism was then examined and closed (position V or VI) using the specially designed external control unit. The area of the eyeWatch™ was then covered with a graft of bovine pericardium and the overlying conjunctival sutured with interrupted 8.0 Vicryl sutures.

Postoperatively, patients were hospitalized for 2 days and then examined on regular intervals. They received a standard postoperative regimen of tobramycin–dexamethasone eye drops in a tapering fashion for 1 month. One patient completed a 12-month follow-up period, and two patients a 6-month follow-up period. On all postoperative intervals, the eyeWatch™ system was adjusted as required in an attempt to achieve acceptable IOP values.

RESULTS

DISCUSSION

The eyeWatch™ has been described by Villamarin et al. and validated in vitro and in vivo.^3,4 Within the mechanism, an eccentrically shaped magnetic disk can be rotated by an externally controlled magnet unit to adjust fluidic resistance. A customized adjustment of aqueous humor outflow can thus be achieved to minimize the risk of hypotony or inadequate lowering of IOP. eyeWatch™ is therefore a continuously adjustable glaucoma drainage device, which allows the dynamic modification of aqueous outflow.^1,3,4 According to its original concept, eyeWatch™ is connected to a non-valved aqueous drainage implant placed intraorbitally.¹ Thus, aqueous flow is mediated by this implant but the rate of drainage is controlled by the eyeWatch™ unit. However, this combined implantation of two aqueous drainage units (i.e., the non-valved implant posteriorly and the eyeWatch™ unit anteriorly) increases surgical time and creates a need for extensive tissue preparation to receive both implants.

The current approach represents a minimally invasive alternative to the standard surgical technique of eyeWatch™ system implantation, reducing surgical time and associated tissue trauma. Moreover, the tube design with multiple perforations along its length implies that aqueous may drain along all the orbital anterio-posterior length, increasing the possibility of reaching non-scarred areas. By selecting larger diameters of the perforations, aqueous outflow may be increased in selected cases. Difficulties in tube insertion encountered in the third patient of this series, may be attributed to scar tissue along the insertion path and may perhaps be overcome by the use of a sharp tip in the insertion catheter, rather than the blunt tip used in all three cases of this series. The proposed technique has also other potential advantages including the possibility of multiple tube insertions, which could be connected to a single eyeWatch™ implant and the individualized selection of an optimal drainage quadrant for each patient, depending on the efficacy of the local vascular elements. The latter point is supported by literature reports on sectorial differences in aqueous outflow depending on the presence of adequate vascularity to each area.^5,6 Moreover, the tube material may be modified by the potential addition of slow-released antimetabolites in an effort to decrease scarring along its length.

Results from the first three cases imply that the proposed technique has potential efficacy, contradicting to some extent the need for a stereotypical larger scale surgical approach. Complications observed, such as the hyphema and vitreous hemorrhage of the first patient, may not be related with the tube technique but with the clinical features of the case (high myopia, previous lens extraction, pseudophakia). The failure to control the IOP in the third case may be attributed to the extensive scar tissue in the retroorbital area encountered, which resulted in trimming part of the length of the tube inserted. The present report is certainly a mere feasibility study on the technique and large prospective studies would be required, along with adequate modifications of the proposed technique. The end point of this approach would be a less invasive but equally effective alternative to standard plated intraorbital implants.

REFERENCES

1. Villamarin A, Roy S, Bigler S, et al. A new adjustable glaucoma drainage device. Invest Ophthalmol Vis Sci 2014;55(3):1848–1852. DOI: 10.1167/iovs.13-12626.

2. Kawamorita S, Hamanaka T, Sakurai T. The early postoperative complications of two different tube ligation methods in Baerveldt implant surgery. J Curr Glaucoma Pract 2014;8(3):96–100. DOI: 10.5005/jp-journals-10008-1170.

3. Villamarin A, Stergiopulos N, Bigler S, et al. In vivo testing of a novel adjustable glaucoma drainage device. Invest Ophthalmol Vis Sci 2014;14(55):7520–7524. DOI: 10.1167/iovs.14-14563.

4. Roy S, Villamarin A, Stergiopulos C, et al. Initial clinical results of the eyeWatch: a new adjustable glaucoma drainage device used in refractory glaucoma surgery. J Glaucoma 2019;28(5):452–458. DOI: 10.1097/IJG.0000000000001209.

5. Van Oterendorp C. Imaging of the intrascleral aqueous drainage system—new insights for glaucoma surgery targeting the trabecular meshwork. Klin Monbl Augenheilkd 2018;235(3):309–314. DOI: 10.1055/s-0042-123193.

6. Cha ED, Xu J, Gong L, et al. Variations in active outflow along the trabecular outflow pathway. Exp Eye Res 2016;146:354–360. DOI: 10.1016/j.exer.2016.01.008.