Glaucoma surgery using microshunts is performed in more than 60 countries around the world.
On January 13, Nagoya University announced that when a vaseline-based ointment, which is widely used in ophthalmology, comes into contact with the glaucoma surgical implant “Pretherflo(R) Microshunt” and “Glaucoma Drainage System” (hereinafter referred to as “Microshunt”), the Microshunt swells and hydrates, changing its shape and hardness.For the first time, it has been evaluated using both clinical examples and laboratory evaluations. This is a joint research project between the medical systems research group led by Associate Professor Kenya Yuki of the University’s Graduate School of Engineering, and the engineering systems research group led by researcher Takato Kajita and lecturer Atsushi Noro (concurrently serving at the Institute for Future Society Creation’s Materials Innovation Research Institute and Center for the Creation of a Decarbonized Society). Published in the Archives of Clinical and Experimental Ophthalmology.
Image from release
(For details, please check the related link ▼)
Glaucoma is the number one cause of blindness among adults in Japan. According to a domestic survey, approximately 5% of people over the age of 40 have glaucoma.
One type of glaucoma surgery that is popular worldwide is one that uses a microshunt. The microshunt is a thin tube-shaped implant with a length of 8.5 mm and an inner diameter of 70 μm, which is inserted into the eye and filled with water (compared to traditional surgery, it has been reported that there are fewer postoperative complications and fewer additional measures are required, and it is currently used in more than 60 countries around the world, making it widely used as an effective option for internal surgery treatment.
Microshunt, ointment using an oily base. Contact with the product is strictly prohibited.
The material used for the microshunt is a special polymer called SIBS, which is also used in stents inserted into the coronary arteries of the heart. For this reason, the manufacturer’s “Instructions for Use” has a warning section that says, “Microshunt can be brought into direct contact with vaseline-based ointments and preparations” to ensure safety.
After exposure to oil-based eye ointment, the microshunt swells and hydrates, changing its shape and hardness.
In this study, we found that after surgery to insert a microshunt, when the conjunctiva that originally covers the microshunt is torn and the microshunt is exposed to the surface of the eye, if an oil-based eye ointment (Vaseline-based eye ointment), which is routinely used in ophthalmology to protect the cornea and prevent infection, is used, the microshunt and the ointment come into direct contact, and the ointment components penetrate into the material, causing the shunt to expand and undergo micro-changes in shape and hardness.
Swelling of the exposed microshunt was confirmed in multiple cases using eye ointment.
Furthermore, in multiple clinical cases where eye ointment was used after surgery with the microshunt exposed from the conjunctiva, the removed microshunts were swollen and thicker than normal ones, and in some cases the material itself was thin, with the fin-like parts tearing off when grasped with surgical instruments.
The oil in the ointment is incorporated into the material, causing it to swell and become moist, increasing its outer diameter by approximately 1.44 times in 24 hours.
To verify this phenomenon, we conducted an experiment in the laboratory in which an unused microshunt was soaked in eye ointment. As a result, the same swelling and swelling as in the clinical case was reproduced.
Furthermore, chemical analysis revealed that after 24 hours of immersion, approximately 45% of the ointment’s total weight had been absorbed by the time the ointment was eaten, and that the main cause of the swelling was that the oil in the ointment had been incorporated into the material.
Important knowledge to prevent problems after glaucoma implant surgery
Based on the present results, there is a concern that Vaseline-based ophthalmic ointment may not be used too quickly if the microshunt is exposed from the conjunctiva in an eye with a microshunt inserted.
The research group acknowledged that, “The joint research carried out between the medical and engineering groups has demonstrated that the microshunt expands well in both patient cases and laboratory experiments, which is an important finding in preventing postoperative problems.”