Petrolatum-based ointment application induces swelling of the PRESERFLO Microshunt

To report the clinical cases of PRESERFLO MicroShunt swelling following exposure to petrolatum-based ophthalmic ointment and to experimentally identify the cause and composition of the swollen MicroShunt.

A retrospective case series and an in vitro experimental study were conducted. The clinical series included three glaucoma patients with swollen MicroShunts after ointment exposure and four patients whose explanted MicroShunts showed no swelling without ointment exposure. In vitro experiments were performed using unused MicroShunts incubated in 0.3% ofloxacin ophthalmic ointment. A time-course immersion study was conducted for 24 h at room temperature, with microscopy documenting dimensional changes. After 24 h and 3 months, swollen devices underwent quantitative analysis using proton nuclear magnetic resonance (¹H-NMR) spectroscopy to determine the relative weight composition of polystyrene-block-polyisobutylene-block-polystyrene (SIBS) and absorbed ointment.

All three MicroShunts exposed to ointment exhibited marked swelling, whereas those without exposure showed no swelling. In vitro, ointment-exposed devices displayed similar swelling, became friable, and fractured after 24 h. Dimensional analysis demonstrated progressive increases, with outer diameter expanding 1.44-fold and fin width 1.29-fold by 24 h. ¹H-NMR analysis showed that swollen devices consisted of approximately 55% SIBS and 45% ointment by weight after 24 h, progressing to 27% SIBS and 73% ointment after 3 months.

Direct contact between petrolatum-based ophthalmic ointment and the SIBS-based MicroShunt induced markedly, time-dependent swelling that compromises the its structural integrity. Thus, the use of ophthalmic ointment should be avoided in patients with an exposed MicroShunt.