Innovations in instrumentation — many resulting from feedback from early adopters in the field — have led to expanded indications for small-gauge vitreoretinal surgery. Driving acceptance of microincision techniques is the potential for several key benefits, among them improved wound construction, less vitreous hemorrhage, faster healing with less postoperative inflammation, improved comfort for patients, and faster visual recovery.

Intraoperatively, these fine-gauge instruments can be safely introduced into small spaces between membranes and retina, serving as multifunctional tools and facilitating tissue dissection. Using the latest generation technology, vitreoretinal surgeons are seamlessly managing more complex cases with the expectation of achieving self-sealing sclerotomies in most cases with no postoperative hypotony or endophthalmitis.

In this supplement, surgeons share their experiences with this rapidly evolving technology, from early challenges to innovative new instrumentation and techniques.

Benefits of Small-gauge Vitrectomy

How does small-gauge instrumentation improve vitreoretinal surgery? Chicago surgeon Yannek Leiderman, MD, PhD, reports three main advantages.

“First, the reduced diameter of the instrumentation in small-gauge vitrectomy systems enables us to access more pathology and operate ever closer to the retina and other structures, particularly when we are working in small spaces, trying to remove vitreous in a controlled fashion,” Dr. Leiderman says. “Second, the smaller instrumentation affords us greater fluidic stability, thereby reducing the turbulence that causes retinal motion in cases of detachment. Third, smaller incision sizes appear to induce less inflammation, more rapid recovery, and less discomfort postoperatively for patients.”

Benefits to patients are also important, as noted by Colin A. McCannel, MD, Los Angeles. “One of the key advantages of small-gauge vitrectomy instrumentation is that the smaller the holes are, the less tissue damage there is, and the less healing has to take place,” he says. “This provides significant benefits to patients in terms of recovery time and discomfort during and after recovery.”

Dr. McCannel also appreciates the advantages of sutureless, self-sealing wounds. “All of the small-gauge instrumentation has been deployed to the marketplace with the idea that it can be used in a sutureless fashion,” he says. “We can insert the trocars in such a way that the holes seal themselves, obviating the need to place sutures to seal the holes to prevent leakage and pressure drops. With each subsequent generation of even smaller gauge instrumentation, the proportion of eyes with low pressures on post-op day 1 has decreased, because the smaller the hole, the easier it is for the tissues to re-approximate and seal well.”

Another benefit of small wounds that heal faster is a reduced potential for infection, says Asheesh Tewari, MD, Ann Arbor, MI. “The trend is definitely toward smaller-gauge instrumentation for all of these reasons,” he says. “That is the future.”

The transition from 20- to 25-, 23-, and now 27-gauge vitreoretinal surgery has not been without its challenges, as early adopters discovered.

Early Limiting Factors

“Some of the challenges we encountered during the development of the initial small-gauge instrumentation — 25-gauge in 2003 — were that the instruments were fairly flexible, the flow through the instruments was considered inadequate by many, and our traditional light sources, which were mainly halogen, were not powerful enough to provide sufficient illumination through the small instrumentation,” Dr. McCannel says.

These disadvantages seemed a fairly logical result of finer-gauge instruments, says Brian C. Joondeph, MD, Denver.

Dr. Leiderman concurs. “In spite of the refinements in the materials used to make vitrectomy needles, probes, forceps, and other instruments, flexibility remains a challenge,” he says. “These instruments are like oars in oarlocks in the eye in that they are inserted through the cannulas and we are pivoting them. As we apply force to the handles of the instruments externally — the smaller the diameter of the instrument, the more apt it is to flex or bend — changing the position of the tip in the eye and making it much more difficult to be precise in the eye.”

As for fluid flow, Dr. Joondeph notes, “Smaller incisions and ports mean less fluid flowing into the eye and less fluid and material flowing out of the eye. According to Poiseuille’s Law, flow is inversely proportional to the fourth power of the radius of the tube through which you are aspirating or infusing, meaning that small changes in the diameter of the vitreous cutter or infusion port lead to very large changes in flow rates. Simply put, you sacrifice flow the smaller you go.”

Similarly, surgeons sacrificed light as gauges decreased in size. “We illuminate our surgical field with a handheld fiber-optic light comprised of many tiny fibers; the smaller the gauge the fewer the fibers that can fit in the light pipe,” Dr. Joondeph says. “That is particularly an issue if a patient has some preexisting cataract that already acts as a filter. Even with the light at full power, I would like it to be brighter. That less-intense illumination was an inherent disadvantage with earlier small-gauge systems.”

Addressing Shortcomings

While early adopters tested the boundaries of small-gauge surgery, most surgeons continued to use 20-gauge instrumentation, which, although large by today’s standards, offers the rigidity and control favored in vitreoretinal surgery, as well as good fluidics because of its fairly large bore.

According to Dr. McCannel, improvements in fluidics and instrument rigidity were realized during the development of 23-gauge instrumentation.

“One of the early adaptations of 23-gauge instrumentation was developed by Dutch Ophthalmic Research Center (DORC) in collaboration with Claus Eckardt, MD, in Germany,” Dr. McCannel says. “It was a major boon at the time, because, to many, it represented a nice compromise between the traditional, familiar 20-gauge and the too flexible, unfamiliar 25-gauge instrumentation. While the 23-gauge addressed some of the challenges related to flow and instrument rigidity, more powerful light sources were also being developed so that the smaller diameter of the fiber optic became less important; however, it was still a limitation.

“Fast forward a few years, when DORC was interested in facilitating smaller-gauge vitrectomy surgery,” Dr. McCannel continues. “The company developed an excellent light-source that is powered by high-intensity LED lights that address some of the issues of output with an incredibly high lumen rating. Immediately, that became more than adequate for 23- and 25-gauge surgery. Furthermore, newer 25-gauge instrumentation was being manufactured with better metals and improved fluidics for slightly better flow than the first generation instrumentation. Small-gauge vitrectomy was getting more sophisticated with continuing interest in even smaller gauge instruments, giving birth to the idea of 27-gauge vitrectomy procedures.”

By 2010, when 23- and 25-gauge vitreoretinal surgeries were becoming the norm, Oshima and colleagues were pushing the small-gauge envelope further, testing the theory that smaller is better in terms of incision size.¹ They developed and evaluated a 27-gauge system that included an infusion line, a high-speed vitreous cutter, an illumination system, and a variety of vitreoretinal instruments.

While the fluid dynamics and cutting efficiency of this prototype system were not on par with 25-gauge surgery at that time, the authors reported no need to transition to a larger gauge, no need for sutures, and no postoperative hypotony. They concluded that 27-gauge vitrectomy surgery was feasible and had the potential to reduce concerns about complications related to wound sealing in selected cases.

A mounting body of evidence along with positive clinical experience with 23- and 25-gauge surgery set the stage for the development of a 27-gauge vitrectomy system. ■

Reference

1. Oshima Y, Wakabayashi T, Sato T, Ohji M, Tano Y. A 27-gauge instrument system for transconjunctival sutureless microincision vitrectomy surgery. Ophthalmology. 2010;117:93-102.