New Innovations in Small-Gauge Instrumentation
Advances in 25-g and 23-g instrumentation are enabling surgeons to achieve outcomes equal to or better than those they can attain with 20-g instruments.
MARC J. SPIRN, MD · ALLEN C. HO, MD
Since 1970, when Machemer introduced pars plana vitrectomy, many innovations have propelled vitreoretinal surgery, facilitating treatment of disease processes that had been difficult or impossible to treat.
For example, after perfluorocarbon liquid (PFCL) was introduced, patients with giant retinal tears could be treated more easily and effectively. Instead of placing patients in a Stryker frame and operating on them upside down (with the surgeon operating while lying on his back), these patients could be treated in a prone position with excellent outcomes. Other major advances have included the adoption of 3-port techniques, endolaser systems, long-acting tamponades, and silicone oils. Recently, there has been another major change in vitreoretinal surgery: the adoption of 25-g and 23-g techniques.
In 2002, de Juan and associates introduced the 25-g transconjunctival trocar-based sutureless vitrectomy system.1 With this system, wound size was smaller, creating a need for smaller instruments. The first generation of these instruments was flexible and, at times, unwieldy, limiting the surgical indications to less complicated cases, such as macular puckers or vitreous hemorrhages. As subsequent generations of instruments have been introduced, 25-g instruments have become more rigid and more advanced surgeries have become possible, including retinal detachment repairs with or without proliferative vitreoretinopathy (PVR).
|Marc J. Spirn, MD, is in private practice at Mid Atlantic Retina. He is also instructor of ophthalmology at Thomas Jefferson University and on the retina service at Wills Eye Institute, both in Philadelphia. He has no financial interests to disclose relevant to this article.|
Allen C. Ho, MD, is in private practice at Mid Atlantic Retina. He is also professor of ophthalmology at Thomas Jefferson University and on the retina service at Wills Eye Institute, both in Philadelphia. He has served as a consultant and has received research funding from Alcon Laboratories, Inc.
When Eckhart introduced his 23-g vitrectomy in 2005, small gauge transconjunctival sutureless vitrectomy with rigid instrumentation became a reality. Twenty-three gauge instrumentation has the advantages of being small like 25-g but with rigidity characteristics similar to those of 20-g instrumentation. The rigidity and enhanced cutting efficiency made 23-g preferable to 25-g in several instances. These include dense vitreous hemorrhages, where the cutter is less likely to get jammed,2 patients who are likely to need extensive endolaser treatment and patients with superior pathology requiring laser treatment, which is easier to access for the more rigid 23-g laser than the more flexible 25-g laser.
The benefits of 25-g and 23-g techniques include improved patient comfort, decreased operative times, and decreased postoperative astigmatism compared to 20-g vitrectomy.3,4 Until recently, however, the major deterrent to performing 25-g or 23-g vitrectomy was a paucity of available instrumentation. Fortunately, over the last several years, the variety and quality of instruments have improved, expanding the indications to perform 25-g and 23-g surgery. In this article, we examine the latest small-gauge instruments and show how they have influenced outcomes and improved surgical processes.
ILLUMINATION AND ILLUMINATED INSTRUMENTS
Whether you choose 25-g or 23-g systems, several instruments or innovations can make complex cases easier. The first consideration is the illumination source. Traditionally, illumination was provided by halogen lighting. More recently, the trend is toward xenon lighting with filtered ultraviolet wavelengths. Although the benefit of this increased illumination may be nominal when performing 20-g surgery, it is critical with 25-g and 23-g instrumentation. The decreased fiber size in the smaller gauge light pipes results in poor illumination with conventional halogen lighting. With a xenon source, however, the lighting is adequate and may supercede conventional 20-g lighting.
Not only does the xenon light source improve light pipe illumination, it also enables production of illuminated instruments. Although these options are still limited compared with 20-g instrumentation, there are several 25-g or 23-g illuminated instruments available. First is the illuminated laser. Although there are straight and curved non-illuminated lasers, these are less versatile because peripheral laser treatment cannot be performed with unassisted scleral depression.
When choosing an illuminated endolaser, you can opt for either a straight or a curved shaft. Straight illuminated lasers are beneficial for pseudophakes, but access to the superior retina can be limited. In phakic individuals, surgeons must take care to avoid lenticular touch when treating peripheral pathology. Curved illuminated lasers enable unassisted treatment of the far periphery and superior retinal pathology while minimizing the risk of lenticular touch. Several products are available in 23-g and 25-g styles, but the 23-g is more user-friendly because of its increased rigidity. The variety of illuminated instruments is one area where 23-g and 25-g instrumentation lags behind 20-g instrumentation, but we believe this will improve with time. The introduction of additional illuminated instruments will likely further improve small gauge bimanual techniques.
One recently introduced illuminated instrument is the 23-g lighted pick. Here, again, the xenon illumination is critical. Use of the lighted pick allows for bimanual surgery, which may be particularly advantageous when repairing a complex tractional retinal detachment (TRD) or peeling PVR. When a 23-g illuminated pick is inadequate or unavailable, another option is to open one sclerotomy to accommodate 20-g instrumentation. Otherwise, if bimanual surgery is desired, the surgeon can always use an illuminated infusion cannula (20-g) or a fourth port with illumination (eg, Tornambe Torpedo) and still use 25-g or 23-g entry for the other three ports.
Additionally, disposable sclerotomy adaptors are now available to convert a 20-g non-cannulated incision back to either 23-g or 25-g to complete the case after using 20-g instrumentation for a portion of the surgery.
Cases that involve peeling, such as macular pucker, macular holes, TRDs, and PVR, are among the most common indications for small gauge surgery. Surgeons can choose from several precision-designed forceps for peeling, including internal limiting membrane (ILM) forceps, end-grasping forceps, and asymmetrical forceps, all available in disposable formats in 23- and 25-gauge. For heavier membrane pathologies, serrated forceps are available in 23-gauge disposable. We have found the ILM forceps particularly versatile and useful.
In most cases, 25-g forceps are equivalent to 23-g forceps. However, when retrieving a posteriorly dislocated intraocular lens or when peeling peripheral PVR, the rigidity of the 23-g forceps can be helpful. In addition, when an epiretinal membrane is particularly taut, an end-grasping forceps or asymmetric forceps can facilitate initiation of the peel. Other instruments that can help initiate a peel include the 25-g pick or the 25-g diamond-dusted scraper.
The vitrector alone can be a useful tool in segmenting or delaminating a TRD. This is especially true with the 25-g or 23-g cutters where the cutter mouth is closer to the tip than with the 20-g vitrector. For difficult cases, delamination or segmentation can be performed with the horizontal scissors. One drawback of small gauge surgery is that no membrane-peeler cutter scissors exists. Because of this, the use of scissors or a bimanual technique may be necessary. The horizontal scissors may also be useful for dissecting pupillary membranes or for creating a retinectomy during a complex retinal detachment repair.
SPECIAL CONSIDERATIONS FOR RETINAL DETACHMENTS
Several innovations have enabled repair of complex retinal detachments with PVR. As we have discussed, PVR can be removed with a variety of forceps or bimanual techniques. During these cases, as with many other retinal detachments, injection of PFCL may be necessary. Unlike the 20-g system, the trocars leave little room to vent around the cannula when injecting PFCL. In this "closed" system, as PFCL is injected, the pressure increases, and it is common to see venous or even arterial pulsations of the optic nerve head. The pressure head can be equilibrated by removing the infusion cannula (which vents the trocar), or by disconnecting the infusion line (which runs the risk of hypotony). One newer innovation is the dual bore 23-g infusion cannula. One bore enables PFCL to be injected, while the other simultaneously allows passive aspiration of intraocular fluid. The cannula prevents high pressure and the need to vent either the port or the infusion line.
Recent reports suggest that retinal detachment repair with silicone oil instillation is possible with 25-g and 23-g instrumentation and that results may be comparable to those achieved with 20-g techniques.5-7 Because silicone oil is viscous, injection through smaller gauge instruments can be time-consuming. When injection of oil is necessary, we prefer 23-g over 25-g because the larger caliber allows more efficient silicone oil injection. The oil can be injected with a 23-g viscous fluid injector. Our preference, however, is to use a 22-g angio-catheter, which has a tapered end. The tapered end fits snugly in the cannula, and oil can be injected more efficiently. Although a 24-g angiocatheter can also be used, the 22-g injection is much quicker and can be used to inject either 1000 centistoke or 5000 centistoke silicone. (Poiseuille's law states the flow rate of liquid is proportional to the radius of the lumen to the fourth power. This means that oil flows 2.4 times more quickly through a 22-g lumen than a 24-g lumen). Although it has been reported that silicone oil does not extrude through sclerotomies that were left open,6 we have seen subconjunctival oil after sutureless vitrectomy, and our preference, therefore, is to suture each sclerotomy. When it is time to remove the silicone oil, 25-g or 23-g instrumentation can be used.8 Our preference, however, is to open one port and remove the silicone oil using an 18-g angiocatheter.
GAINING ON 20-G
Over the last several years, many new instruments have been introduced for 25-g and 23-g surgery. As a result, indications for small gauge surgery are now comparable to those for 20-g surgery. With proper planning and knowledge, surgeons can achieve outcomes equal to or better than those achieved with 20-g surgery. When the proper instrumentation is not available, surgeons should consider a hybrid technique. As instrumentation continues to evolve, however, 25-g and 23-g techniques will likely continue to gain popularity. RP
- Fujii GY, De Juan E Jr, Humayun MS et al. A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery. Ophthalmology. 2002 Oct;109(10):1807-12.
- Shinoda H, Nakajima T, Shinoda K et al. Jamming of 25-gauge instruments in the cannula during vitrectomy for vitreous haemorrhage. Acta Ophthalmol. 2008 Mar;86(2):160-4.
- Misra A, Ho-Yen G, Burton RL. 23-gauge sutureless vitrectomy and 20-gauge vitrectomy: a case series comparison. Eye. 2008 Jun 6.
- Valmaggia C. Pars plana vitrectomy with 25-gauge instruments in the treatment of idiopathic epiretinal membranes. Klin Monatsbl Augenheilkd. 2007 Apr;224(4):292-6.
- Riemann CD, Miller DM, Foster RE, Petersen MR. Outcomes of transconjunctival sutureless 25-gauge vitrectomy with silicone oil infusion. Retina. 2007 Mar;27(3):296-303.
- Oliveira LB, Reis PA. Silicone oil tamponade in 23-gauge transconjunctival sutureless vitrectomy. Retina. 2007 Oct;27(8):1054-1058.
- Altan T, Acar N, Kapran Z, Unver YB, Ozdogan S. Transconjunctival 25-gauge sutureless vitrectomy and silicone oil injection in diabetic tractional retinal detachment. Retina. 2008 Aug 25.
- Kapran Z, Acar N. Removal of silicone oil with 25-gauge transconjunctival sutureless vitrectomy system. Retina. 2007 Oct;27(8):1059-1064.