Endoscopic free electron laser technique development for minimally invasive optic nerve sheath fenestration

Purpose: This study proposed to develop a technique for efficiently accessing the posterior orbital space using endoscopy and attempted application of free electron laser (FEL) energy, biopsy forceps, electrocautery, and CO2 insufflation to posterior orbital tissues. Methods: Through an inferior transconjunctival incision, access to the posterior orbital space was attempted in 14 eyes of 7 non-survival pigs. FEL energy (6.1 mu m, 30 Hz, delivered via 250 mu m hollow-glass waveguide), biopsy forceps, and monopolar electrocautery application were endoscopically attempted in the posterior orbit. CO2 gas insufflation effects were assessed by analyzing arterial blood gases at 30-minute intervals for 1.5 hours. Results: The posterior orbit was accessed in 13 of 14 eyes, the optic nerve was encountered, and FEL energy was applied in 8 of 14 eyes. Use of biopsy forceps and electrocautery were successful. Although ANOVA results for arterial blood gas changes were not statistically significant, visibility was adequate without CO2 insufflation. Conclusions: The posterior orbit was endoscopically accessed and the optic nerve was exposed and successfully treated with FEL energy. CO2 insufflation did not alter blood gases, but did not further enhance visibility in this study.