Better safe than sorry! Results from an ex vivo study demonstrate that the thulium fiber laser may cause eye injury without standard protection
Min Joon Lee1, Simon Czajkowski2, Ariel Gershon3, Thomas Sabljic 3, Gad Acosta4, Kate Kazlovich5, Jason Y. Lee1,2.
1Division of Urology, Department of Surgery, University of Toronto, Toronto, ON, Canada; 2Division of Urology, Department of Surgery, University Health Network, Toronto, ON, Canada; 3Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; 4Medical Engineering, Toronto General Hospital, University Health Network, Toronto, ON, Canada; 5Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
Introduction: We conducted a study using an ex vivo pig eye model to evaluate whether a thulium fiber laser induces ocular injury in the context of inadvertent exposure to the laser beam without eye protection, with laser safety goggles, and with prescription eyeglasses.
Methods: A 365 μm thulium fiber laser (SOLTIVETM SuperPulsed Laser, Olympus Corp) was positioned at a set distance (0 cm, 5 cm, 8 cm, and 10 cm) from a freshly harvested (<12 hours) porcine eyeball and pointed towards the center of the cornea, after which the laser was activated for one second at select laser settings for lithotripsy (0.2 J at 50 Hz, 0.5 J at 20 Hz, and 1 J at 10 Hz) and soft tissue ablation (2 J at 10 Hz and 1 J at 50 Hz). The experiment was repeated with laser safety goggles and prescription eyeglasses. Thermal injury was assessed by histopathological analysis.
Results: Without any eye protection, corneal injury was observed even at 10 cm away for one lithotripsy setting (1 J at 10 Hz) and both tissue ablation settings. All thermal injuries observed were superficial only, except for at 0 cm distance, where deep layer injury was observed. No injury to the lens was identified at any setting in our study. Laser safety goggles offered complete protection regardless of setting or distance. Partial protection was demonstrated with prescription glasses: histopathological damage was observed for both soft tissue ablation settings and only at 0 cm for two lithotripsy settings (0.5 J at 20 Hz and 1 J at 10 Hz).
Conclusions: The thulium fiber laser can induce ocular injury at close distances and at higher power settings. The use of laser safety goggles during endourological procedures confers complete protection at all settings; prescription eyeglasses confer partial protection. Further study is warranted.
