EyeWatch Implant

Key points at a glance

1. What is the EyeWatch Implant?

Glaucoma is the leading cause of irreversible blindness worldwide ¹⁾. Elevated intraocular pressure (IOP) is the most important risk factor for the onset and progression of the disease. IOP causes mechanical strain on retinal ganglion cell (RGC) axons at the lamina cribrosa, leading to axonal transport disruption and apoptosis ⁵⁾.

When adequate IOP reduction cannot be achieved with medication or laser therapy, surgical treatment is chosen. Glaucoma drainage devices (GDDs) are effective for cases where trabeculectomy has failed or for refractory glaucoma eyes with a history of intraocular surgery ²⁾. Currently, the two main GDDs used are the Baerveldt glaucoma implant (BGI) and the Ahmed glaucoma valve (AGV).

However, conventional GDDs have challenges in postoperative IOP management. Non-valved BGIs carry a risk of early postoperative hypotony, while valved AGVs have a hypertensive phase occurring in 53–83.5% of cases. Once implanted, fine adjustment of flow is difficult with either device.

The EyeWatch (eW) is the world’s first adjustable glaucoma drainage device, developed by Rheon Medical (Switzerland). Its main feature is the ability to non-invasively adjust postoperative aqueous humor outflow via an external magnetic control unit.

4. Device Structure and Adjustment Method

Device Body

The eW consists of the following components:

Internal rotating magnetic disk: rotates in response to an external magnet
Deformable silicone tube: opens and closes in conjunction with the rotation of the magnet
Bearing system: Smooth rotation of the magnet
Nozzle and outlet: Form the outflow tract for aqueous humor

The device dimensions are as follows:

Item	Specification
External dimensions	6.5×5.8 mm
Thickness	0.8 mm
Anterior chamber insertion size	25-gauge

The eW is also compatible with the eyePlate silicone drainage plate and valveless shunts such as the BGI.

eyeWatch Pen (eWP)

The eWP functions as an external control unit.

Structure

Compass: Mounted on one end. Measures the position of the eW.

Magnet: Mounted on the other end. Adjusts the opening and closing of the tube.

Setting Range

0 (fully open): Maximum aqueous humor outflow.

6 (fully closed): Blocks aqueous humor outflow.

7 levels: Allows fine adjustment according to clinical conditions.

During surgery, a sterile eWP is used to set the eW to 5 or 6 to prevent early postoperative hypotony. An outpatient eWP is used for postoperative adjustments based on intraocular pressure.

Comparison with Conventional Glaucoma Drainage Devices

The characteristics of existing major glaucoma drainage devices are as follows:

BGI (Baerveldt Glaucoma Implant): Plate area 350 mm² (anterior chamber insertion type) or 250 mm² (pediatric). It is a non-valved type without a pressure-regulating valve, requiring tube ligation or stenting to prevent early postoperative overfiltration ¹⁾
AGV (Ahmed Glaucoma Valve): Plate area 184 mm² or 96 mm² (pediatric). It has a built-in pressure-regulating valve in the plate to prevent hypotony, but has a high incidence of postoperative hypertensive phase.
eW: Used in connection with BGI or eyePlate. Allows external 7-step flow adjustment, capable of managing both hypotony and hypertension.

Q How is intraocular pressure adjustment performed with the eyeWatch Pen (eWP)?

The compass at one end of the eWP confirms the position of the eW, and the magnet at the other end is placed over the eW and rotated to adjust the opening of the internal tube from 0 (fully open) to 6 (fully closed). For hypotony, the setting is turned toward closure; for hypertension, toward opening. Adjustment can be performed non-invasively in the outpatient clinic.

5. Surgical Technique and Clinical Outcomes

Indications

The indications for eW are as follows¹⁾.

Refractory glaucoma with failed filtering surgery
Glaucoma eyes with a history of intraocular surgery
Many types including secondary glaucoma
Refractory hypotony after previous BGI surgery (rescue surgery)

Surgical Technique

The basic technique of glaucoma drainage device surgery is as follows.

Incise the conjunctiva over the plate placement area for more than 1 quadrant but less than 2 quadrants
Inject anesthetic under Tenon’s capsule
Place traction sutures on two extraocular muscles to secure the surgical field
Place the plate 1 mm posterior to the muscle insertion and fix it with nylon sutures
Inject viscoelastic material into the anterior chamber to deepen it
Puncture with a 23G needle 1.5 to 2 mm posterior to the limbus
Insert the tube approximately 2 mm into the anterior chamber and fix it to the sclera with nylon sutures

The eW is placed by connecting it to the tube line of the BGI or eyePlate. During surgery, the setting is adjusted to 5–6 (almost fully closed) using a sterile eWP to prevent excessive filtration.

Clinical Outcomes

Roy Prospective Study (Multicenter Trial)

Fifteen eyes with refractory glaucoma that had failed multiple glaucoma surgeries were included. The eW was implanted in combination with BGI, and patients were followed for an average of 15.6 ± 3.5 months. The complete success rate (without medication) was 40%, and the overall success rate was 93%. Mean IOP decreased significantly from 26.2 ± 6.8 mmHg preoperatively to 11.9 ± 2.8 mmHg at 12 months postoperatively (P < 0.001). The mean number of medications decreased from 3.0 ± 0.7 to 0.8 ± 0.9. The only complication was incomplete wound closure not related to device function.

Roy Retrospective Comparative Study (eW-B vs AGV)

The main results of the study comparing eW-BGI and AGV are shown below.

Parameter	eW-B group	AGV group
Complete success rate	67%	50%
Overall success rate	89%	58%
Complication rate	0%	25%

21 eyes were followed for a mean of 13.2±3.4 months. Mean IOP decreased significantly from 27.3±7.0 to 12.8±2.4 mmHg in the eW-B group and from 24.8±9.0 to 13.8±3.6 mmHg in the AGV group (P<0.05). Mean number of medications decreased from 2.9±0.8 to 0.2±0.4 in the eW-B group and from 3.0±0.7 to 0.3±0.7 in the AGV group. Failure rate was 11% in the eW group versus 42% in the AGV group.

Detorakis (study using perforated tube)

A perforated silicone tube (4 cm) was connected to the eW instead of a plate valve and implanted in three blind painful eyes. Two eyes were successful, maintaining IOP below 15 mmHg for 12 and 6 months, respectively. One eye required difficult surgery due to scar tissue and was unsuccessful with IOP of 40 mmHg at 6 months postoperatively.

Elahi (rescue case report)

For refractory hypotony (persisting for 3 months) after BGI surgery, an eW was connected to the existing BGI. On postoperative day 1, IOP was 22 mmHg with eWP set to 5/6 open. On day 4, IOP dropped to 3 mmHg, so eW was set to 6/6 (fully closed). IOP then increased to 6 mmHg at 1 week, 11 mmHg at 4 weeks, and 12 mmHg at 6 weeks. At week 10, when IOP reached 13 mmHg, it was reopened to 5/6. Thereafter, IOP remained stable between 8 and 12 mmHg for 6 months.

Long-term outcomes of conventional glaucoma drainage devices (reference)

In the 5-year results of the TVT study (tube vs trabeculectomy), the cumulative failure rate was 29.8% in the tube group and 46.9% in the trabeculectomy group, which was significantly higher in the trabeculectomy group ²⁾. On the other hand, a systematic review of glaucoma drainage devices showed no significant difference in mean IOP at 12 months postoperatively between the Ahmed and Baerveldt groups ³⁾. The mean number of glaucoma medications was 1.22 at 12 months and 1.23 at 24 months ³⁾.

Q What are the advantages of EyeWatch compared to conventional glaucoma drainage devices?

The greatest advantage of eW is that it allows non-invasive adjustment of aqueous humor outflow from the outside after surgery. Conventional glaucoma drainage devices cannot finely adjust flow, limiting the management of hypotony (common in BGI) and hypertensive phase (common in AGV). eW can avoid both complications through 7-step flow adjustment, and initial studies report a complication rate of 0%.

6. Pathophysiology and Significance of Flow Adjustment

IOP and Glaucomatous Optic Neuropathy

IOP cannot be summarized as a single value; it varies over time, by location within the eye, and by measurement method ⁵⁾. Elevated IOP causes mechanical strain at the level of the lamina cribrosa, leading to damage to RGC axons. In experimental glaucoma, axonal damage at the lamina cribrosa has been confirmed ⁵⁾.

The mechanism of RGC death involves depletion of neurotrophic factors due to impaired axonal transport. When axonal transport is blocked, the supply of neurotrophic factors from target neurons is interrupted, reactivating apoptosis ⁵⁾.

Challenges in IOP Management with Conventional Glaucoma Drainage Devices

Glaucoma drainage devices consist of a silicone tube inserted into the eye and a plate that collects aqueous humor. The resistance to aqueous outflow is mainly determined by the connective tissue capsule around the plate, but capsule formation varies greatly among individuals and is difficult to predict.

BGI (non-valved): There is a risk of overfiltration in the early postoperative period. The tube is ligated to temporarily block outflow, but this results in a hypertensive phase for about one month until the ligature dissolves, requiring glaucoma eye drops or oral medications. The incidence of hypotony in BGI is 4.5%, significantly higher than 0.4% in AGV ²⁾
AGV (valved): Designed to prevent overfiltration with a pressure-regulating valve, but the periplate tissue is exposed to inflammation, leading to a hypertensive phase. Its incidence is high, ranging from 53% to 83.5%.

Solution with eW

eW allows external adjustment of flow in 7 steps, enabling the following management:

Early postoperative period: Setting 5–6 (almost fully closed) prevents overfiltration
During hypertensive phase: Change the setting to a more open direction to increase outflow
During hypotony: Change the setting to the closed direction to limit outflow
Long-term management: Adjust as needed over time according to the progression of capsule formation or age-related changes

This adjustment can be performed non-invasively in an outpatient setting and does not require additional surgery, which is a major advantage. In Elahi’s case, eW was connected for refractory hypotony after BGI surgery, and IOP was successfully stabilized by simply changing the eWP setting.

7. Latest Research and Future Prospects

Roy and Mermoud confirmed that eW effectively lowers IOP over a two-year period in patients with a history of glaucoma surgery.

However, the following challenges remain at present.

Accumulation of evidence: Existing studies are limited to small-scale prospective and retrospective studies. Large-scale randomized controlled trials (RCTs) are needed.
Long-term outcomes: The longest follow-up is two years, and data on long-term safety and efficacy beyond five years are lacking.
Standardization of implantation technique: As reported by Detorakis, implantation may be difficult in cases with severe scar tissue.
Expansion of indications: The applicability to various disease types such as pediatric glaucoma, secondary glaucoma, and rescue surgery needs to be examined.
Use in Japan: Currently, eW has not received pharmaceutical approval in Japan, making its use difficult domestically.

Known serious risks of glaucoma drainage devices include hypotony, implant exposure, endophthalmitis, and long-term corneal endothelial damage¹⁾. The extent to which eW can reduce these complications in the long term remains to be determined by future research.

Q Can the EyeWatch implant be used in Japan?

Currently, eW has not received pharmaceutical approval in Japan. The two types of glaucoma drainage devices available in Japan are the Baerveldt glaucoma implant and the Ahmed glaucoma valve. Introduction of eW to Japan will require future clinical trials and approval procedures.

8. References

European Glaucoma Society. European Glaucoma Society Terminology and Guidelines for Glaucoma, 6th Edition. Br J Ophthalmol. 2025;109(Suppl 1):1-230.
日本緑内障学会. 緑内障診療ガイドライン（第5版）. 日眼会誌. 2022;126:85-177.
Ong SS, Nti AA, Engel LM, et al. Outcomes and complications of glaucoma drainage devices: a systematic review and meta-analysis. Surv Ophthalmol. 2023;68(4):578-590.
American Academy of Ophthalmology. Primary Open-Angle Glaucoma Preferred Practice Pattern. San Francisco: AAO; 2020.
Pitha I, Du L, Nguyen TD, Quigley HA. IOP and glaucoma damage: The essential role of optic nerve head and retinal mechanosensors. Prog Retin Eye Res. 2023;97:101232.

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