Thiel cadaver eye as a training model for sub-Tenon blocks: a feasibility study

Abstract Background: Regional anesthesia education, especially for ocular procedures, necessitates reliable surgical training models. While cadaveric models offer anatomical fidelity, conventional embalming methods may compromise tissue integrity. We aimed to assess the effectiveness of Thiel cadavers for training in sub-Tenon blocks by evaluating ocular tissues and measuring insertion forces. Methods: Experimental design, using twenty eyes from ten Thiel cadaver heads. These cadavers were specifically prepared to test the administration of sub-Tenon blocks. The research was conducted in a controlled laboratory setting appropriate for handling cadaveric materials and conducting precise measurements. Each cadaver eye underwent an initial ultrasound examination, and its axial length was noted. An intravitreal injection of heptastarch solution followed, to re-establish the eye's sphericity. After this volume injection, the axial length and intraocular pressure were measured again. Mock sub-Tenon blocks were administered in 2 separate quadrants of the eye, with insertion forces measured using a pressure gauge. Main outcome measurements were macroscopic assessment of the ocular tissue layers and the insertion forces required for the sub-Tenon blocks. Results: Four of twenty eyes (20%) retained near-natural sphericity, with the remaining requiring volume injection to approximate physiological shape and pressure. The conjunctiva and Tenon’s layer were intact, and correct cannula placement was achieved in all cases. The average maximum cannula insertion force was 2.92 Newtons. Conclusion: These findings suggest that Thiel cadavers are a promising model for training in sub-Tenon blocks, despite the challenge of often desiccated and involuted eyes.