Observational study finds MicroShunt implants in glaucoma patients swell or rupture — Evidence Review

A new study from Nagoya University links petrolatum-based eye ointments to swelling and rupture of the widely used PRESERFLO MicroShunt glaucoma implant. Most prior research on glaucoma implant safety has not addressed this specific risk, but generally agrees that device-related complications are a critical concern for patient outcomes (1, 5, 8).

• While earlier studies identified general risks associated with glaucoma drainage devices, this is the first to demonstrate a clear chemical interaction between a commonly used ointment and implant material, highlighting a unique, previously overlooked complication (5, 8).
• Related literature consistently emphasizes the need for long-term safety data and awareness of device-specific adverse events, but has not previously documented the risk of petrolatum-based ointments causing implant swelling or rupture (1, 5).
• The findings build on existing concerns about implant exposure and infection risk (2), and further illustrate that both the physical location and chemical environment of implants are important factors in post-surgical management.

Study Overview and Key Findings

The use of minimally invasive glaucoma surgery (MIGS) devices like the PRESERFLO MicroShunt has increased globally, owing to their favorable safety and efficacy profiles compared to traditional filtration surgeries. However, the chemical compatibility of these implants with common post-operative treatments, such as eye ointments, has not been thoroughly investigated until now. This study is among the first to provide combined clinical and experimental evidence that petrolatum-based ointments can directly compromise the integrity of the MicroShunt, raising new questions about standard post-surgical care and device safety.

Property	Value
Organization	Nagoya University, Nagoya University Hospital, Graduate School of Medicine, Graduate School of Engineering
Journal Name	Graefe's Archive for Clinical and Experimental Ophthalmology
Authors	Ryo Tomita, Taiga Inooka, Kenya Yuki, Takato Kajita, Atsushi Noro
Population	Glaucoma patients with MicroShunt implants
Sample Size	n=7
Methods	Observational Study
Outcome	Swelling and rupture of MicroShunt implants
Results	Three implants swelled and two ruptured after ointment exposure.

Literature Review: Related Studies

To contextualize these findings, we searched the Consensus paper database, which aggregates over 200 million research papers. The following queries were used to identify relevant studies:

1. glaucoma implant safety concerns
2. eye treatment complications glaucoma
3. implant rupture eye ointment exposure

Related Studies: Key Topics and Findings

Topic	Key Findings
What are the general safety concerns and complications of glaucoma implants?	- MIGS and tube shunts provide effective IOP reduction but are associated with device-specific complications such as malposition, exposure, infection, and erosion (1, 2, 5, 8). - Long-term safety data are limited; complications can be transient or serious, including vision loss (1, 5, 7, 8).
How does implant location and exposure affect risk of complications?	- Inferiorly placed implants have higher risks of exposure and infection compared to superior implants (2). - Exposure increases the risk of device failure and infection, with site selection being a modifiable risk factor (2, 8).
What is known about chemical/material compatibility and device failure?	- No prior studies have directly linked petrolatum-based ointments to implant swelling or rupture, but device failure due to material incompatibility is recognized as a possible complication (5, 8). - The importance of understanding the chemical environment of implants is emphasized (5).
How do alternative glaucoma treatments compare in safety and efficacy?	- Alternative implants (e.g., bimatoprost, XEN gel stent) also reduce IOP but have distinct safety profiles, with complications ranging from corneal endothelial loss to device extrusion (3, 4, 5). - Trabeculectomy and tube shunt surgeries are associated with frequent but often self-limited complications (6, 7).

---

What are the general safety concerns and complications of glaucoma implants?

The broader literature underscores that glaucoma drainage devices and MIGS procedures, while beneficial for intraocular pressure (IOP) control, carry risks of device-related complications. These include, but are not limited to, malposition, exposure, infection, and, in rare cases, vision loss. The new study's identification of petrolatum-induced implant swelling adds a new dimension to these concerns, highlighting chemical as well as mechanical risks.

• Device-related complications, such as malposition, obstruction, and exposure, are well-documented risks of glaucoma implants (1, 5, 8).
• Most complications are transient and self-limited, but serious events such as vision loss or endophthalmitis can occur (5, 7, 8).
• Long-term safety data for many newer implants are still lacking, necessitating ongoing monitoring and reporting (1, 5).
• The new study provides a previously unreported example of how a common post-operative medication can compromise device integrity.

How does implant location and exposure affect risk of complications?

Several studies have shown that the physical location of glaucoma implants, particularly inferior versus superior placement, influences the risk of exposure and subsequent infection. The new study complements this by demonstrating that device exposure, when combined with petrolatum ointment use, significantly increases the risk of swelling and rupture.

• Inferior implants are at greater risk of exposure and infection than superiorly placed devices (2).
• Exposed implants are more vulnerable to infection and physical damage (2, 8).
• Site selection and surgical technique are modifiable risk factors for device longevity (2).
• The present study suggests that, in addition to location, chemical exposures (e.g., ointments) must be considered in post-operative care.

What is known about chemical/material compatibility and device failure?

Prior to this study, the literature primarily addressed mechanical and infectious complications, with little focus on chemical incompatibility between medical devices and topical treatments. The new findings emphasize the need for greater awareness of how common substances can interact with implant materials.

• Device failure due to material incompatibility is recognized but understudied; most reports focus on physical rather than chemical causes (5, 8).
• The importance of understanding chemical properties of implant materials and their interactions with the ocular environment is increasingly acknowledged (5).
• The novel evidence linking petrolatum-based ointments to MicroShunt swelling and rupture suggests a need for updated clinical guidelines.
• Manufacturer warnings about chemical exposures are not always widely recognized or followed in practice, presenting a gap in education and risk mitigation.

How do alternative glaucoma treatments compare in safety and efficacy?

Alternative implants and surgical approaches, such as the bimatoprost implant and the XEN gel stent, have been shown to reduce IOP with varying safety profiles. These alternatives are associated with their own sets of complications, but none have previously been linked to ointment-induced device failure.

• Both bimatoprost and XEN implants reduce IOP effectively, but can cause corneal cell loss, implant extrusion, or infection (3, 4).
• Trabeculectomy and tube shunt surgeries often result in early postoperative complications, though most are transient (6, 7).
• No prior reports have associated ointment use with device swelling or rupture in these alternative treatments, suggesting the new finding is specific to the SIBS polymer of the MicroShunt.
• Ongoing surveillance of device-specific risks and adverse events is essential for patient safety (5, 7).

Future Research Questions

Further research is needed to understand the broader implications of this new complication, optimize post-operative care strategies, and develop guidelines that minimize risks for patients with glaucoma implants.

Research Question	Relevance
Does petrolatum-based ointment exposure affect other types of glaucoma implants?	Understanding whether this risk is unique to the MicroShunt or extends to other devices is crucial for comprehensive patient safety (5, 8).
What are the long-term effects of oil-induced swelling on MicroShunt performance?	The impact of subclinical swelling on device efficacy and patient outcomes remains unknown and requires longitudinal study (1, 5).
Are alternative post-operative treatments safer for patients with MicroShunt implants?	Identifying safe and effective alternatives to petrolatum-based ointments is important for preventing complications while maintaining patient comfort (5, 7).
How widely are manufacturer warnings about chemical exposure followed in clinical practice?	Assessing adherence to manufacturer guidelines can reveal gaps in clinician awareness and inform targeted educational interventions (5).
What mechanisms drive the absorption of oil-based substances in SIBS polymers?	Elucidating the physicochemical interactions between ointments and implant materials may inform the design of more robust devices (5).

---

This research highlights a new and preventable risk for patients with glaucoma implants, emphasizing the necessity for ongoing vigilance in both device design and clinical practice. As the use of minimally invasive glaucoma devices expands, understanding and mitigating all forms of complication—mechanical, infectious, and chemical—will remain a critical priority.