Lancet-blade Trocars Encounter Less Resistance

By Hakan Kaymak, MD
 

Transconjunctival 23- and 25-gauge trocar systems provide a self-sealing option, as the surgical wound seals and heals without sutures due to the small incision size. Most trocar inserters contain a sharp needle-like stiletto entry device that creates a linear or curved cut through the scleral wall. The outer segment of the trocar is generally cylindrical, so that the surgeon can pivot the surgical instrument into the globe.

Various parameters play a role in determining the amount of force that must be applied during the initial piercing process, including the sharpness of the tip of the trocar, the thickness of the sclera and rigidity of the scleral resistance, and the intraocular pressure of the patient’s eye. The initial puncture is accomplished when the distal end of the trocar needle tip applies enough pressure to cause the tissue structure to be displaced. The length and form of the cut performed may influence the amount of dilatation force and friction force needed.

In a clinical study, the cutting profiles and geometrical contours of 11 different 23-gauge trocar systems were analyzed, and the penetration forces were measured.1 The study found that the most important factor in reducing the penetration forces required was related to the design of the edges on the bevel face. Lancet blades required remarkably low piercing and cutting forces, inducing a symmetrical wound architecture and linear wound apposition. The “sharpest” system tested in the study was the lancet-pointed needle from Oertli. This recently introduced system included a snap-on lock infusion line for more flexibility and a double-slotted sealing membrane. (The US Food and Drug Administration has not approved this system.)

Many vitreoretinal surgeons now prefer to use novel blades with improved surgical beveled geometries for 23- and 25-gauge transconjunctival vitreoretinal surgery. Using these novel blades, the surgeon creates a self-sealing surgical wound, first by directing the surgical blade substantially parallel to the eye surface, then redirecting the blade to follow the general curvature of eye globe, and finally redirecting the blade to enter the interior of the eye. Recently introduced beveled trocar blades represent significant improvements over earlier needle-style trocars. The bevel design appears to reduce the amount of mechanical force required to penetrate tissue and insert the trocar system. These innovations have led to less resistance as the blade enters the tissue, smoother trocar insertion, and more efficient wound closure with better healing characteristics.

1. Meyer CH, Kaymak H, Liu Z, et al. Geometry, penetration force, and cutting profile of different 23-gauge trocars systems for pars plana vitrectomy. Retina. 2014;34(11):2290-2299.

Hakan Kaymak, MD
• senior partner, Internationale
Innovative Ophthalmochirurgie,
Breyer & Kaymak & Klabe Eye Surgery,
Düsseldorf, Germany
• Financial disclosure: paid consultant
for Alcon, Bausch + Lomb, and Oertli
h.kaymak@augenchirurgie.clinic

 

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New Retina MD delivers cutting-edge content to retina specialists in their first 15 years of practice. Each issue provides fresh insight from younger physicians plus established mentors on clinical and nonclinical issues affecting ophthalmologists in the earlier stages of their careers. NRMD features surgical pearls, clinical research endeavors, practice management, medical reimbursement and policy, continuing educational requirements, financial planning, innovations, and more.