Current microincision vitrectomy surgery (MIVS) with 25- or 23-gauge instrumentation has simplified the vitrectomy procedure and offers numerous potential advantages over traditional 20-gauge surgery including shorter operating time, reduced corneal astigmatism, diminished conjunctival scaring, less postoperative inflammation, improved patient comfort, and, in some cases, earlier visual recovery.1-6 Are current procedures, however, really the simplest and most minimally invasive? Currently, complex techniques are required for self-sealing 23- and 25-gauge wounds.2,7,8 Additionally, reports of wound-sealing–related complications, such as hypotony and endophthalmitis, have surfaced as a result of increasing use of MIVS with 23- and 25-gauge instrumentation.9-11
Prior to the introduction of MIVS, smaller-gauge instruments have been used for postoperative management of vitrectomized eyes. For example, we have performed transconjunctival fluid-fluid exchange and fluid-air exchange through a 27-gauge needle for many years, and there are no reports of serious complications related to wound integrity with a 27-gauge needle. Therefore, I propose that 27-gauge (0.40 mm) may be the best-suited technology for sutureless MIVS.
DEVELOPMENT OF 27-GAUGE VITRECTOMY SYSTEM
A crucial concern in developing small-gauge systems is reduced endoillumination. Fortunately, the recent introduction of more powerful light sources using xenon light (Accurus High Brightness Illuminator, Alcon Laboratories, Inc., Fort Worth, TX; Photon, Synergetics, Inc., St. Charles, MO; BrightStar, DORC, Zuidland, Netherlands) and mercury vapor light (Photon II, Synergetics, Inc.) has enabled us to develop smaller-gauge illumination tools.12 We have developed a one-step chandelier probe (Synergetics, Inc.) consisting of a 27-gauge needle socket and a 29-gauge inner light fiber (Figure 1A).13 Another type of 27-gauge chandelier system using twin optical fibers (Twinlight chandelier illumination system, DORC) has recently become commercially available (Figure 1B).14 Both types of 27-gauge chandelier illumination are sufficient to illuminate the fundus (Figures 1C and D). At the end of surgery, the scleral wound perfectly self-seals after simple removal of the 27-gauge fibers.
Also available are 27-gauge asymmetrical microforceps (Synergetics, Inc.) for 27-gauge non-vitrectomizing vitreous surgery (Figure 2).15 At present, several types of 27-gauge fine-tip microforceps such as end-gripping forceps (DORC) and pick forceps (ASICO, Westmont, IL) are commercially available for 27-gauge macular surgery. The stiff shaft and fine tip on the forceps enable grasping of thick or thin internal limiting membranes.
Development of a practical 27-gauge vitreous cutter was the most crucial step for establishing a 27-gauge vitrectomy system. We developed a prototype pneumatic 27-gauge cutter in collaboration with DORC (Figure 3). The port area of the cutter is wider than that of commercially available 25-gauge cutters (Y. Oshima, unpublished data, 2008). A shorter shaft provides rigidity similar to a conventional 25-gauge cutter. Using a high-speed camera, we evaluated the 27-gauge cutter's duty cycle. Surprisingly, the duty cycle of the 27-gauge cutter was equal to or slightly better than that of a 25-gauge cutter at 1,000 or 1,500 cpm (Y. Oshima, unpublished data, 2008). Based on the duty cycle evaluation and infusion flow rate measurements, we found that the pressure of the vented gas forced infusion system (Accurus High Brightness Illuminator, Alcon Laboratories, Inc.) can be set within a normal range of 20 to 30 mm Hg, providing safe control of intraocular pressure (IOP) during vitrectomy.
In addition to these basic instruments for 27-gauge vitrectomy, several 27-gauge accessories, such as membrane spatula, diamond-dusted membrane scraper, and endolaser probe, have been developed for expanding the surgical indications of 27-gauge vitrectomy.
SURGICAL INDICATIONS, PROCEDURES, AND PRELIMINARY RESULTS
Current indications for transconjunctival 27-gauge vitrectomy are listed in Table 1. Although the performance of the current prototype 27-gauge vitreous cutter has not yet reached the level for treating complex proliferative vitreoretinal pathologies, which often require extensive peripheral vitreous shaving and manipulation, this system is now feasible to supersede a 25-gauge system to treat macular diseases, simple vitreous hemorrhage, and moderately severe proliferative diabetic retinopathy.
The 27-gauge system offers several advantages over the currently widely used 23- and 25-gauge systems. Using the 27-gauge system removes concerns about complications related to wound-sealing. In a pilot study approved by the institutional review board, we have performed 27-gauge vitrectomy in 28 eyes of 28 patients for a variety of vitreoretinal diseases, including epiretinal membrane proliferation, idiopathic macular hole, diabetic vitreous hemorrhage with fibrovascular membrane proliferation, and nonclearing vitreous opacity. The settings for 27-gauge vitrectomy are similar to that for 23- and 25-gauge instrumentations; however, complex techniques for creating a self-sealing wound, such as angled-insertion technique7,8 or two-step entry method,2 are no longer required. The 27-gauge vitrectomy can begin immediately after sclerotomies at the pars plana by simple vertical insertion using a 27-gauge needle. A 27-gauge trocar-cannula system is available but not necessary for all cases because the small gauge eliminates concerns about extensive vitreous incarceration in the small sclerotomy. After simple removal of all instruments, surgery can be closed at once and all sclerotomies self-sealed completely without the need for suturing. Using the 27-gauge system, opening and closing procedures can be simplified, and this may contribute to saving total operating time with this system. In our series, the IOP of all 28 eyes was stable from postoperative day 1 without any eyes encountering hypotony (≤7 mm Hg) throughout the follow-up period (mean, 6.3 months), suggesting perfect self-sealing structures of the 27-gauge wounds. The 27-gauge sclerotomy can no longer be identified even on postoperative day 1, and there are no remarkable changes on the ocular surface in most cases (Figure 4). Because of its small size, the 27-gauge cutter can play several roles concurrently during surgery (ie, as a cutter, aspirator, peeling forceps, and membrane scissors). Reducing the use of various instruments for manipulation may eliminate time wasted in instrument exchanges and also contribute to saving total operating time. The mean operating time in the 28-eye study was 30 minutes. No eyes required conversion to larger-gauge instrumentation during surgery. No serious intra- or postoperative changes were observed during follow-up. Anatomic success was achieved in all study eyes, including visual improvement by three lines or more in 70% at the latest follow-up examination.
FUTURE PERSPECTIVE
Although the development of 27-gauge vitrectomy is an ongoing project and has not yet been established as a widely accepted system, the feasibility and safety of 27-gauge vitrectomy in selected cases have been demonstrated and confirmed.16 Further development and refinement of the 27-gauge instruments' stiffness and functionality will continue over the coming years and allow us to establish an ultra-minimally invasive surgery system for vitreoretinal diseases in the near future.
Yusuke Oshima, MD, PhD, is an Assistant Professor in the Department of Ophthalmology, Osaka University Medical School, Japan. Dr. Oshima has no proprietary interest or conflict of interest in any aspect of this article, and received no royalties from the sale of the devices mentioned in this article, nor is he a patent holder of these devices. He can be reached at +81 6 6879 3456; fax: +81 6 6879 3458; or via e-mail: oshima@ophthal.med.osaka-u.ac.jp.
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