Investigation of Needle Characteristics Using an Animal Model for Improved Outcomes in Anterior Chamber Paracentesis

The current standard of care to perform an anterior chamber paracentesis involves the use of a multipurpose market needle and syringe. The use of standard needles for this purpose may result in injury to the patient due to increased force with insertion and increased globe displacement during the procedure. This research investigates the current market needle characteristics and the impact of each needle characteristic on force. Several comparative trials were conducted to evaluate the needles. Needle characteristics of interest were gauge, primary bevel angle, number of bevels in the lancet, and needle hub geometry. Measurements of corneal insertion forces were made using a synthetic thermoplastic polyurethane medium, and bovine and porcine models. Needle safety was investigated with corneal abrasion experiments. Reduced insertion force was observed with lower lancet primary angle. There was no difference based on the number of bevels in the lancet. Rounded hub geometry had minimal distribution to the corneal epithelium. Needle characteristics impact the force needed for needle insertion into the tissue. Since higher force can lead to increased risk and less efficiency during the procedure, reducing this force may improve the outcomes of the procedure. Needle entry can be reduced by designing an improved needle that includes a lower gauge and reduced primary angle of the lancet.