27-gauge presents new paradigm of intraocular precision for vitrectomy

September 15, 2017

Modern 27-gauge equipment for vitrectomy has introduced a new paradigm in vitreoretinal surgery marked by enhanced precision and control.

Reviewed by Christopher D. Riemann, MD

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.”

Physical principles

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.

Gentle to the eye

Another advantage of the small 27-gauge instrumentation is that the smaller incision size means less trauma to the eye. As a result, operated eyes tend to be very quiet and white on the first day after surgery. Patients have less pain, faster healing, and need less medication to control inflammation.

“In addition, when performing 27-gauge pars plana vitrectomy, it is even more feasible to use subconjunctival anesthesia in patients who are on anticoagulant medications,” Dr. Riemann said. “This eliminates the risk of peribulbar and retrobulbar regional blocks.”

Advances in instrumentation

Excessive flexibility of 27-gauge instrumentation was a valid objection when the technology was first introduced, but the current generation probes are much stiffer.

“Modern 27-gauge instruments are stiffer than first generation 25-gauge instruments and actually approach the stiffness of modern 25-gauge equipment,” Dr. Riemann said.

A broad array of ancillary 27-gauge devices, including light pipes, forceps, pics and scissors, as well as subretinal injection, oil infusion, dual bore, and SideFlō cannulas are available from various instrument manufacturers.

Surgeons transitioning to 27-gauge vitrectomy should expect a brief learning curve. They need to proactively place the cutter into a position where its effect is needed.

“The tip must be placed right into the vitreous gel being removed,” Dr. Riemann said. “Even being 1 mm away from the vitreous skirt will leave you cutting water and give a false impression that the technology provides slow and inefficient vitrectomy.”

Dr. Riemann pointed out that when used correctly, 27-gauge vitrectomy provides previously unheard of intraocular precision. “We still have a need for larger gauge instrumentation in certain cases, but once surgeons have tried 27-gauge vitrectomy, they will not go back,” he added. “This is especially true of complex diabetic dissections.”

 

Christopher D. Riemann, MD

E: criemann@cincinnatieye.com

This article is based on a presentation given by Dr. Riemann at the 2017 Retina World Congress. He is a paid consultant and speaker for Alcon Laboratories and receives funds for research. He is a paid consultant to and receives royalties from intellectual property licensed to MedOne Surgical.