Continuing Development of 27-gauge Vitrectomy Systems: Where Are We Now?
Yusuke Oshima, MD
Since Eugene de Juan, MD, first introduced the current concept of transconjunctival sutureless vitrectomy with a trocar-cannula system and 25-gauge instrumentation,1,2 microincision vitrectomy systems (MIVS) with 25- or 23-gauge instruments have evolved radically over the past several years.3
There is no doubt that MIVS has simplified the vitrectomy procedure and that it offers numerous potential advantages over traditional 20-gauge surgery, including shorter operating time, reduced corneal astigmatism, diminished conjunctival scarring, improved patient comfort, and in some cases, earlier visual recovery.3-7
Recent innovations and improvements seem to have settled several concerns in the early years of MIVS. Stiffer instruments and wide-angle viewing systems have eliminated the frustration with tool fragility. A more powerful light source combined with a chandelier system have improved the endoilluminating brightness through a small-gauge optic fiber. The new generation of vitrectomy machines have dramatically improved the cutting efficiency of small-gauge vitrectomy probes.8-10
CRITICISMS OF SMALL-GAUGE VITRECTOMY
The most serious criticisms regarding the current 23- and 25-g systems have focused on complications related to wound sealing, such as leakage, hypotony, and postoperative infectious endophthalmitis. Although the recent refinement of trocar-cannula systems has ergonomically improved their self-sealing architectures, special techniques are still required. Complete self-sealing wounds are not yet achievable in every case, even with 25-g systems, especially in patients who have thin scle ras or who have had extensive peripheral vitreous shaving.
The common theory (or basic rule) regarding surgical wounds is that “much smaller is much better.” Actually, surgeons in Japan have been shifting dramatically from 20- to 23-g systems and from 23- to 25-g systems, along with the development of ergonomic instrumentation and new-generation vitrectomy machines over the years (Figure 1).11,12 According to a marketing survey by Alcon Japan, Ltd., more than 70% of the users of the Constellation Vision System (Alcon Laboratories, Inc., Fort Worth, TX) prefer 25-g systems for most cases.
Figure 1. Current trends of MIVS in Japan.
On the basis of the above-mentioned aspects of modern MIVS, the gauge size for MIVS will likely decrease in the future. In fact, before the introduction of 25- and 23-g MIVS, much smaller-gauge instrumentation had been used for postoperative management.
For example, we have for many years performed transconjunctival fluid-fluid exchange and fluid-air exchange in vitrectomized eyes with 27-gauge needles. We have not encountered any serious complications related to wound integrity with a 27-g (0.40 mm) needles, which some have proposed as the optimal size for easy self-sealing of scleral wounds.
Recent innovations, such as the advent of powerful light sources, techniques for building up stiffer instrumentation, and high-performance vitrectomy systems, have also encouraged us to launch the development of a 27-g vitrectomy system over the past several years.13
CURRENT STATUS OF THE DEVELOPMENT OF 27-G VITRECTOMY SYSTEMS
In 2008, we were very excited to first report preliminary results using a first generation 27-g system. Although at that time it was used only in the selected cases, mainly macular disease and simple vitreous hemorrhage, both the anatomical and visual results were promising.13
Remarkably, there was no need to transition to a larger gauge, no suturing was required, and no hypotony was observed in any of the study cases. Encouraged by the promising pilot study results, we have succeeded in collaborating with two companies (DORC, Zuidland, Netherlands; and Synergetics, Inc., St. Charles, MO) to launch a 27-g system pack for macular surgery.
Both commercially available 27-gauge system packages include a 2,500-cpm high-speed pneumatic vitreous cutter, a wide-angle illuminating light pipe, an infusion tube with a trocar-cannula system, and a micro-membrane forceps. The system from DORC is compatible with two vitrectomy machines, the Accurus (Alcon) and Associates (DORC). The system from Synergetics can be used with the Accurus only.
In addition to these systems, we are working with Alcon to launch a 27-g ultra-vit probe system with the Constellation Vision System in the near future (announced at the Frankfurt Retina Meeting, March 10-11, 2012 in Frankfurt, Germany).
When developing a smaller-gauge vitrectomy system, the most crucial concerns may be about reduced endoillumination and cutting efficiency through small-gauge lumen. The introduction of powerful light sources, using xenon light and mercury vapor light, which have been featured in the new-generation vitrectomy machines as the standard illumination light sources, has fortunately enabled us to develop smaller-gauge illumination tools.
Currently, not only the 27-g wide-angle illuminating light pipe packaged in the 27-g pack, but also the 27-g chandelier endoilluminating optic fibers, are commercially available from several manufactures for use with 27-g systems for more challenging cases, such as a 27-gauge twin-light chandelier system (Dorc International, Zuidland, Netherlands) and a 29-/30-gauge dual chandelier fiber system (Synergetics, O’Fallon, MO).
Both types of 27-g chandelier fibers have maximum output reaching to more than 20 lumens, which is sufficient to endoilluminate the fundus.9,14 Development of a practical 27-g vitreous cutter is also a key step for establishing a 27-g vitrectomy system.
Very recently, the second-generation spring/pneumatic 27-g cutter from Dorc and Medical Instrument Development Laboratories, Inc., (San Leandro, CA) have become commercially available, featuring a normal shaft length (32 mm) and a maximum cutting rate of up to 2,500 cpm with higher duty cycles.
Using a high-speed camera, we evaluated the new generation 27-g cutter's duty cycle to be approximately 45% to 50% at 2,000 cpm and 35% to 40% at 2,500 cpm, which is equal to or slightly better than that of currently commercially available 25-g spring/pneumatic cutters.
Based on the duty cycle evaluation in the new-generation 27-g vitreous cutter and infusion flow rate measurements, we found that the pressure of the vented gas-forced infusion system (Accurus, Alcon) can currently be set within a range of 25 to 40 mm Hg, providing safe IOP control during vitrectomy.
Although the vitrectomy performance (cutting efficiency and flow volume) of the current 27-g vitrectomy probe does not exceed that of 23- or 25-gauge systems and is approximately 70% compared to that of spring/pneumatic 25-g vitreous cutters, the performance of 27-g vitrectomy with good duty cycles is feasible and sufficient to be applied clinically for macular surgery and selected challenging cases, such as primary retinal detachment and moderate to severe PDR.
When the next generation 27-g cutter, in conjunction with the new-generation machines, launches in the near future, we believe the surgical indications for 27-g vitrectomy will be expanded more widely.
In addition to these basic instruments for 27-g vitrectomy, several 27-g accessories (Figure 2), such as micromembrane forceps (Dorc; Ascico, St. Louis, MO; Synergetics), membrane spatula (Dorc, Ascico), angled scissors (Dorc, Ascico), back-flush needle (Dorc), 38-/27-g subretinal injection needle (MedOne Surgical, Inc., Sarasota, FL), diamond-dusted membrane scraper (Synergetics), diathermy probe (Dorc), and endolaser probe (Dorc,
Synergetics) have been developed to expand the surgical indications of 27-g vitrectomy for challenging diabetic vitrectomies and submacular injections.
Figure 2. Variations among commercially available 27-g accessories.
Currently, most intraocular manipulations can be performed with 27-g instruments, except for special cases, such as PVR and severe trauma cases, and the procedures are similar to or much simpler than those performed with conventional 23- or 25-g systems.
TECHNIQUES, INDICATIONS, AND CLINICAL EXPERIENCES WITH 27-GAUGE SYSTEMS
The most distinctive characteristic of the 27-g system that makes it superior to the larger-gauge MIVS systems is the simplicity of creating rigid, self-sealing wounds. The surgeon can begin 27-g vitrectomy immediately after creating sclerotomies at the pars plana by one-step vertical insertion. Complex techniques for creating a self-sealing wound, such as angled-insertion techniques or two-step entry methods, are no longer required.
Using the 27-g system will simplify opening and closing procedures, which may save total operating time. Also, because of the small size and multifunctionality of the 27-g cutter, reducing the use of various instruments for manipulation in complex cases will minimize the time wasted in instrument exchanges and, as a result, also contribute to the reduction of total operating time.
After simple removal of all instruments, surgeons can close at once, and all sclerotomies can self-seal completely without the need for suturing, even in cases with thin scleras, extensive peripheral vitreous shaving, or multiple surgeries.
Surgeons will no longer need to care about wound sealing–related complications when using 27-g systems. The postoperative findings, including the anterior segment, are in most cases perfect, even on the first day after surgery.
The 27-g vitrectomy cutters, about which lack of rigidity was one of the major concerns, have improved to be stiff enough while featuring a stiffer sleeve. Thanks to the improvement of the cutting efficiency, as described above, the current indications for transconjunctival 27-g vitrectomy have expanded (Table).
|Table. Current Indications for 27-gauge Vitrectomy|
Epiretinal membrane proliferation
Idiopathic or secondary macular hole
Macular traction syndrome
Macular edema associated with
� diabetic retinopathy
� retinal vein occlusion
Persistent pseudophakic cystoids macular edema
Subinternal limiting membrane hemorrhage
Simple vitreous hemorrhage
Primary rhegmatogenous retinal detachment
Moderate proliferative diabetic retinopathy w/ or w/o focal tractional
Similar to the early years after the introduction of 25-g systems, the primary indications for a 27-g system were macular diseases and simple vitreous hemorrhage. More recently, it has been useful for treating primary retinal detachment and moderately severe diabetic cases, along with the development of a variety of accessories in 27-g.
Based on our clinical experiences with more than 100 cases with the 27-g system, it is no doubt feasible that this system will supersede the current 25- and 23-g systems, at least for treating macular diseases (Figure 3) and simple vitreous hemorrhages (presented at the American Society of Retinal Specialists annual meeting August 24-29, 2012, in Las Vegas, NV).
Figure 3. 27-g vitrectomy for diabetic macular edema. Sequential procedures for combined surgery: A. Phacoemulscification through a 2.2-mm clear corneal incision. B. Setting a standard three-port trocar-cannula system with a 27-g chandelier illumination for transconjunctival microincision vitrectomy surgery. C. Transconjunctival microincision vitrectomy for creating posterior vitreous separation. D. Brilliant blue G–assisted internal limiting membrane peeling. E. Posterior capsulotomy using a 27-g vitreous cutter following intraocular lens implantation through a corneal incision. F. Completing self-sealing of the super-otemporal corneal incision and three scleloromies.
More recently, we obtained overall favorable surgical outcomes in 40 cases with moderate to severe PDR as well (presented on subspecialty day at the AAO annual meeting in 2011 in Orlando, FL).
The 27-gauge cutter can be much more easily inserted into the tiny space between the membrane and the retina. Through wide-angle fundus viewing, it is also easy to carry out bimanual membrane dissection with a 27-g system (Figure 4). Nevertheless, overall we had fewer chances to perform bimanual manipulation in the 27-g diabetic series that we did with 23- or 25-g systems, suggesting that the 27-g cutter with a single hand is sufficient for several roles.
Figure 4. Twenty-seven–gauge vitrectomy for tractional retinal detachment Sequential procedures for combined surgery: A. A 27-g vitrectomy is ready immediately after the creation of 27-g sclerotomies by simple perpendicular incision with a 27-g trocar-cannula system through the pars plana. B. The vitrectomy machine used was the Accurus (Alcon Laboratories, Inc., Fort Worth, TX). The VGFI system estimated the optimal pressure at 30 mm Hg, which was used for 27-g vitrectomy with cutting rates ranging from 1,500 cpm to 2,500 cpm and an aspiration pressure of 600 mm Hg. C. The surgery was performed under chandelier illumination with wide-angle viewing and a magnified contact lens for macular work as necessary. Fibrovascular membranes were cut and removed using a 27-g high-speed vitrectomy cutter and a single hand, instead of vitreoretinal scissors. D. A bimanual technique using membrane forceps and a vitrectomy cutter was performed. Insertion of the blunt tip of the cutter into the spaces between the membranes and detached retina is much easier with the 27-g system than with 25- or 23-g cutters. E. In cases with strong membrane-retina adhesion, 27-g angled scissors are manufactured also for separation of the thickened fibrovascular membranes. F. Bimanual technique is also applied for hemostasis, applying diathermy in the left hand and a vitreous cutter in the right hand. The bleeding can be simultaneously aspirated and coagulated under chandelier illumination though wide-angle viewing. G. A 27-g curved endolaser probe is manufactured for panretinal photocoagulation in advanced PDR cases. H. At the end of surgery, after simple removal of all inserted instruments, the surgery was concluded without sutures.
We did not observe any eyes that required conversion to larger-gauge instrumentation during surgery, nor did we observe any eyes that had serious intraoperative or postoperative complications attributed to the 27-g system during follow-up.
The final goal of transconjunctival surgery is to achieve perfect, self-sealing wounds with stable postoperative IOP from the first day after surgery, with tiny changes on the ocular surface — limited subconjunctival hemorrhages and scars and acceptable operating time with minimal intra- and postoperative complications — as well as favorable anatomic success and early visual rehabilitation.
The 27-g system may have advanced one step closer to these final goals, compared with the current 23- and 25-g systems. Although the development of 27-g vitrectomy is an ongoing project, and it has not yet been established as a widely accepted system, its feasibility and safety in selected cases have been demonstrated and confirmed.
The new-generation machines, featuring dual-pneumatic driven technology, allow for ultrahigh cutting rates with duty cycle control. The 27-g systems, with this new technology in the near future, will achieve much higher performance.
Similar to the recent evolution in 23- and 25-g systems, further development and refinement of 27-g instruments’ functionality are under way and will continue over the coming years, allowing us in the future to establish this system for ultra–minimally invasive surgery for the full spectrum of vitreoretinal pathologies. RP
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|Yusuke Oshima, MD, is an associate professor of ophthalmology at the Osaka University Graduate School of Medicine in Suita, Japan, and a visiting professor of ophthalmology at the Nankai University Medical School, Tianjin, China. Dr. Oshima is an international board member of Alcon Laboratories and a consultant to Topcon Medical Laser Systems and Synergetics. He has received lecture fees and travel support from Alcon Laboratories, Carl Zeiss Meditec, DORC International, Synergetics, Santen Japan, and Senju Japan, but he has received no proprietary interests or royalties from any companies with regard to any products mentioned in this article. Dr. Oshima can be reached at firstname.lastname@example.org.|