Widely used petrolatum-based eye ointments may cause swelling and rupture of glaucoma implants, according to new research from Nagoya University in Japan. The study is the first to provide both clinical and experimental evidence that these ointments can compromise the PRESERFLO MicroShunt, a device used in over 60 countries for glaucoma treatment.
Glaucoma is a disease that damages the optic nerve, often due to increased intraocular pressure caused by blocked fluid drainage. An estimated 76 million people worldwide are affected by this condition. The MicroShunt is designed to help drain fluid from the eye, reducing complications after surgery and lessening dependence on additional medications.
The implant is made from a polystyrene-block-polyisobutylene-block-polystyrene (SIBS) block polymer, which offers flexibility and biocompatibility. However, this material can absorb oil-based substances such as petrolatum, leading to changes in its shape and function.
Manufacturer guidelines specify that "the MicroShunt should not be subjected to direct contact with petrolatum-based (i.e., petrolatum jelly) materials, such as ointments and dispersions." Despite this warning, it is not widely followed in clinical settings.
Researchers led by Tomita, Assistant Professor Taiga Inooka, Associate Professor Kenya Yuki from Nagoya University Hospital and Graduate School of Medicine, along with Dr. Takato Kajita and Junior Associate Professor Atsushi Noro from the Graduate School of Engineering, studied seven patients who had their MicroShunt implants removed for various reasons. Their findings were published in Graefe's Archive for Clinical and Experimental Ophthalmology.
In three cases where the implant was exposed outside the conjunctiva and treated with petrolatum-based ointment, all devices showed swelling; two ruptured. In three other cases where no ointment was used and the implant remained covered by conjunctiva, there were no structural changes. One case involved an exposed implant without ointment use; it did not swell.
Laboratory tests confirmed these results: unused MicroShunts immersed in petrolatum-based ointment swelled significantly within 24 hours. Measurements indicated that after one day in ointment, the outer diameter increased by 44%, while chemical analysis revealed oil components accounted for up to 73% of total weight after three months.
The researchers concluded that absorption of oil-based ingredients causes swelling. They recommend clinicians avoid using petrolatum-based ointments on patients with exposed MicroShunt implants and consider alternative treatments post-surgery. Further studies are needed to determine if non-rupturing swelling affects device performance.
"Our study found that commonly used medical materials can cause unexpected complications if their chemical properties and usage environments are not fully understood," Noro stated. "From both medical and engineering perspectives, we emphasize the importance of understanding the chemical properties of medical materials and appropriately managing their usage environments."
