An efficient capacitive sensing scheme for an ophthalmic regional anesthesia training system

Ophthalmic regional blocks are critical preoperative procedures involving the insertion of a syringe needle into the orbital cavity at such a position and angle that akinesia and analgesia is achieved without damage or harm to the eye and its associated musculature. A training system that accurately represents the orbital anatomical features and provides qualitative feedback on the performed anesthetic technique, can be of immense help in reducing risks involved in regional block administration. In this paper, a training system that employs a special but simple capacitive sensing scheme has been developed. A rapid prototyped eye-model has been used to ensure anatomical accuracy. Capacitive transmitter electrodes placed on the orbital wall along the length of the extraocular muscles are excited with a special excitation sequence and the displacement current at the needle of the syringe is measured using simple electronic unit and a Data Acquisition System, enabling the developed Virtual Instrument to detect the depth of penetration and proximity of the syringe needle to the ocular muscles. Additionally, the system detects needle touch of the muscles accurately. The proposed electrode array system and excitation schemes have been validated on a prototype system thus demonstrating its usefulness for practical training purposes.