Modern 27-gauge equipment for vitrectomy has introduced a new paradigm in vitreoretinal surgery marked by enhanced precision and control.
“The small port size of 27-gauge vitrectomy probes, combined with ultra-high cut rates, excellent duty cycles, and high vacuum, add up to a smaller sphere of influence, which means that the ability of the cutter to reach out and pull matter in is restricted to an area very close to its tip,” said Christopher D. Riemann, MD, retinal specialist, Cincinnati Eye Institute, Cincinnati, OH.
With the resulting increased precision and control, the vitrectomy cutter becomes a multifunction tool. It can be used safely on the surface of the retina as a vertical scissors for segmentation, as a horizontal scissors for delamination, or as an active pick for membrane peeling.
“High cut rates, high vacuum, and excellent duty cycles dramatically increase cutter efficiency,” Dr. Riemann said. “The 27-gauge cutter pulverizes and removes material that enters into the cutter port. Even lensectomy is often possible.”
Dr. Riemann explained that sphere of influence is proportional to port size, vacuum or flow, and duty cycle, and inversely proportional to cut rate.
“The beauty of the 27-gauge cutter is that maximum vacuum can be applied with a greater degree of safety right at the surface of the retina,” Dr. Riemann explained. “With 23-gauge or 25-gauge vitrectomy probes–which have much larger port geometries–reducing sphere of influence to a point where retinal surface work with the cutter alone is safe and can be accomplished by lowering vacuum levels. The problematic trade-off is that at the required low vacuum levels, it dramatically reduces cutter efficiency.”
A laboratory study by Pravin Dugel, MD, and colleagues showed the difference in sphere of influence using 23-gauge, 25-gauge, and 27-gauge vitrectomy probes, while keeping duty cycle, cut rate, and vacuum settings constant. The measured attraction distance was 0.55 mm using the 27-gauge cutter, 0.80 mm for the 25-gauge instrumentation, and 1.02 mm for the 23-gauge probe, Dr. Riemann said.