Application of Originally Designed Polymer Micro-Shunt in Open-Angle Glaucoma Surgery

Surgical treatment of glaucoma has occupied first place in the recent years, and in a number of cases it is the method of choice even when revealed for the first time. The experience gained by the Eye Clinic of Nizhny Novgorod Regional Clinical Hospital named after N.A. Semashko shows, that more than 50% of patients with glaucoma who sought medical aid in 2013–2014 required surgical treatment.

At present, special attention is paid to glaucoma drainage surgery. There is a wide variety of drainage devices available for eye surgeons, but there are no reliable data to confirm the advantages of this or that model [1–3]. Nowadays micro-shunting is widely used at the first stage of surgical treatment in primary open-angle glaucoma patients [4]. However, drainage surgery has certain disadvantages. The materials used for these devices are frequently far from ideal: they are heavy and tend to cut and acidize. Specific characteristics and complications of well-known implanted glaucoma shunts are described in a number of papers by foreign and Russian authors [5–7]. Inadequate shunt position makes reimplantation rather complicated, traumatic and requires special surgical equipment [6, 7]. Search for the solution of these problems leads to the development of new technologies.

The aim of the investigation was to assess the efficiency of the original polymer micro-shunt application in open-angle glaucoma surgery.

Materials and Methods. 31 open-angle glaucoma patients (31 eyes) with elevated intraocular pressure (IOP) aged 16 to 82 years were followed-up in our clinic. Of them 23 patients (23 eyes) had simple primary open-angle glaucoma, 5 patients (5 eyes) pseudoexfoliative open-angle glaucoma, 3 patients (3 eyes) secondary open-angle glaucoma. 16 patients (16 eyes) suffered from glaucoma stage III, 14 (14 eyes) — stage IV. One patient with stage II underwent micro-shunt implantation in the course of a single-step surgical intervention for vitreal block developed after YAG-laser capsulotomy, where the first step required anterior vitrectomy and peripheral iridectomy. Visual acuity varied from 0.2 (with or without correction) to abnormal light projection, initial IOP level was 27–38 mm Hg. All patients underwent partial deep sclerectomy with implantation of the original polymer micro-shunt.

For control we used a group of 29 patients who underwent standard sinus trabeculectomy and included 21 patients with glaucoma stage III, 6 patients with stage II, 2 patients with stage IV. Visual acuity varied from 0.5 to normal light projection, IOP was 28–40 mm Hg.

The micro-shunt [8] is made of oligo carbonate methacrylateand represents a square hollow tube 2.5 mm long, with 0.5 mm diameter and 0.2 mm diameter of the inner hole. The needle cutoff angle is 45°. At the needle point there are two additional lateral anti-lock openings 0.15 mm in diameter. The micro-shunt consists of two parts: the needle, which is placed in the anterior chamber, and supporting elements to fix between the surface flap and the deep layers of sclera (Figure 1). The shunt is manufactured by Reper NN company (Nizhny Novgorod, Russia).

---

Figure 1. Original glaucoma micro-shunt, model C-1

---

Before the operation and in the postoperative period all patients were subject to complex examination including visometry, Maklakov tonometry, electronic tonometry and tonometric testing with GlauTest-60 device (Russia). The patients with preserved visual functions also underwent computed static perimetry and optical tomography of the optic nerve disc and nerve fiber layer. Maximum follow-up period lasted 24 months.

This study was approved by the Ethic Committee of Nizhny Novgorod State Medical Academy and compliant with the Declaration of Helsinki (the Declaration was passed in Helsinki, Finland, June, 1964, and revised in October, 2000, Edinburg, Scotland). All patients gave written informed consent for the scientific analysis of their data.

Operative technique. A fixation suture was put on the cornea, conjunctiva incision was made 5 mm away from the limbus (Figure 2 (a)). After hemostasis a surface scleral flap of 1/2–1/3 sclera thickness and about 3.5×3.5 mm in size was cut out with its base toward the limbus (Figure 2 (b)). Then a paracenthesis was formed at the corneal part of the limbus for the period of 9 h, and viscoelastic was introduced into the anterior chamber via the paracenthesis. Under the superficial sclera flap of the limbus transient part a hole was made with a 23G needle, through which the micro-shunt was implanted with smooth branch forceps (Figure 2 (c) and (d)).

---

Figure 2. Stages of the operation

---

Then four sutures were placed on the sclera, an uninterrupted suture was put on the conjunctiva and Tenon's capsule.

Results and Discussion. All patients of the main and control groups were followed up from 5 months to 2 years (mean 15.2 months) to receive the remote results of the operation.

All main group patients achieved pronounced hypotensive effect on the first day after the surgery. Average IOP equaled 10.2 mm Hg. Essential reduction and stabilization of ophthalmotonus due to the outflow improvement was revealed on the basis of long-term electronic tonometry data (Table 1).

---

Table 1. Hydrodynamic indices in different terms of the follow-up period in open-angle glaucoma patients with the original micro-shunt

---

Visual functions remained unchanged. According to computed threshold perimetry data in 19 patients with preserved visual functions and its program statistical evaluation, perimetry indices remained unchanged in 56.3% of cases, 29.5% of patients showed positive dynamics, 13.3% showed insignificant decrease of light sensitivity.

Marked IOP reduction, up to mean 8.3 mm Hg, was observed in the control group on the first day after the surgery. However, in the long term (9 months after the surgery) IOP reached 24 mm Hg in 35.4% of cases, which required administration of hypotensive medications (Figure 3). According to the computed perimetry data negative dynamics was observed in 28.3% of cases.

---

Figure 3. Dynamics of intraocular pressure using standard technique and the novel shunt

---

In the course of treatment, complications caused by initial severity of the impairment and severe concurrent pathology occurred both in the main and control group. However, analyzing the data in the postoperative period we registered a less number of complications after micro-shunt implantation (Table 2). The total number of complications in the control group was 5 (16.1%), in the main group 11 (37.9%).

---

Table 2. The number of complications in the main and control groups (absolute number/%)

---

Conclusion. Application of the original micro-shunt in antiglaucomatous surgery provides stable hypotensive effect without additional conservative therapy throughout the course of the follow-up. As compared to sinus trabeculectomy, this surgery results in decrease of complications in the postoperative period and stabilization of visual functions, making the application of such micro-shunts a promising surgical approach to the management of open-angle glaucoma patients.

Study Finding and Conflict of Interest. This research was not financed by any sources, and there are no conflicts of interest associated with the research.