The dual-bore cannula was introduced by Stanley Chang, MD, more than 30 years ago during the heyday of 20-gauge sclerotomy–based pars plana vitrectomy surgery. At that time, it was used to deliver liquids such as perfluoro-n-octane liquid (Perfluoron, Alcon) and vital dyes to the posterior segment while allowing passive equilibration of IOP through a vent port.
As trocar-based small-gauge pars plana vitrectomy surgery became popular, 23-, 25-, and 27-gauge dual-bore cannulas based on Dr. Chang's original idea were developed to fit through the smaller trocars. Unfortunately, these early small-gauge dual-bore cannulas had a problematic safety profile: Retinal injury from axial jet effect during injection of liquid and unacceptable IOP rise from reduced outflow venting were substantial barriers to their functionality and safety.1-3
The design of the DualBore SideFlo– cannula (MedOne Surgical) mitigates some of the safety issues of early generation small-gauge dual-bore cannulas.
The product's design innovations include moving the egress port for injected medications to the distal lateral shaft (Figure). This adjustment eliminates the axial flow vector and replaces it with a gentler tangential vector. The egress port is an oval, resulting in a fan-like egress of liquids and a further reduction of the egress jet effect.
Figure. The device's design includes multiple vent ports along the shaft of the cannula and an oval egress port at the distal end.
Multiple vent ports were added along the shaft of the cannula, substantially improving outflow facility. This has resulted in better IOP equilibration during injection.
This generation of the dual-bore cannula does not reduce rigidity or increase costs; it is priced the same as the earliest generation of the device.
In the OR, this cannula's fluidic design results in safe, smooth, and rapid delivery of intraocular liquids without axial jet pressure injury to the retina or closure of the optic nerve from overpressurization of the globe. Measured venting performance of the 23-, 25-, and 27-gauge SideFlo– cannulas is much better than first-generation dual-bore cannulas, approximating the performance of dual-bore devices that are one gauge size larger. Venting efficiency of the 23-, 25-, and 27-gauge SideFlo– actually slightly exceeds that of the earlier 20-, 23-, and 25-gauge devices, respectively.4
I routinely use this device to inject vital dyes as well as heavy liquids, and occasionally I use it to manage silicone oil marring of a silicone IOL.5 I suggest that surgeons who are comfortable with embracing innovation consider adding this device to their OR instrumentation.
1. Kim YJ, Jo S, Moon D, et al. Analysis of the intraocular jet flows and pressure gradients induced by air and fluid infusion: mechanism of focal chorioretinal damage. Invest Ophthalmol Vis Sci. 2014;55(6):3477-3483.
2. Malerbi FK, Maia M, Farah ME, Rodrigues EB. Subretinal brilliant blue G migration during internal limiting membrane peeling. Br J Ophthalmol. 2009;93(12):1687.
3. Lee JE, Yoon TJ, Oum BS, Lee JS, Choi HY. Toxicity of indocyanine green injected into the subretinal space: subretinal toxicity of indocyanine green. Retina. 2003;23(5):675-681.
4. Toygar O, Berrocal MH, Charles M, Riemann CD. Next-generation dual-bore cannula for injection of vital dyes and heavy liquids during pars plana vitrectomy. Retina. 2016;36(3):582-587.
5. Mi CW, Sisk RA, Petersen MR, Riemann CD. New surgical applications for the Sideflo– cannula. Retina. 2017;37(2):400-401.