Abandon the 20-gauge vitrectomy? Let’s not be hasty.
WILLIAM E. SMIDDY, MD

Small-gauge vitrectomy (SGV) has opened new possibilities in vitrectomy surgery, but the question of whether its benefits surpass those of standard 20-gauge vitrectomy has not been definitively answered. Before we surgeons abandon the 20-gauge technique, let us remember its 40-year track record in more than 10 million cases, the full array of instrumentation, and the fact that direct inspection and controlled closure of sclerotomies have worked well. For the majority of us, 20-gauge vitrectomy instrumentation continues to be our first choice for the most complex cases.

SGV really involves three interrelated issues: smallversus large-gauge incisions, sutureless closure, and disposable instrumentation. Undeniably, usage of the newer technique is increasing markedly, and many surgeons perform most cases with SGV.1 Metrics to compare systems, however, have not been suitably applied. Six valid reasons to replace 20-gauge with 25-gauge instrumentation might include better results, faster recovery, less morbidity, fewer complications, lower expense, and faster surgery. How does the newer system compare on these points?

RESULTS AND RECOVERY
Probably the fairest assessment of the literature is that SGV’s results are equivalent to those of 20-gauge vitrectomy for the most straightforward cases,^2,3 but what about more complex ones? SGV is not purported to offer better results. Some investigators have found patients’ visual recovery to be greater at 1 month after SGV, but no distinct differences have been found at 6 months.⁴ One study reported greater comfort for patients 1 week postoperatively with SGV,⁵ presumably due to less conjunctival inflammation.⁶ This finding begs the questions, how much discomfort is there really with 20-gauge vitrectomy, and therefore, how much of a benefit is SGV in this regard?

COMPLICATIONS
Are there fewer complications with SGV? If anything, the contrary is true. Several studies have suggested a higher rate of endophthalmitis,^7-9 possibly related to a higher rate of postoperative hypotony^9-12 with SGV. Unsutured wounds might be expected to leak or to cause a vitreous wick leading to these complications more frequently. To be fair, the most recent studies report a lesser disparity as surgeons have improved wound architecture.^2,13-15 How steep is that learning curve, though?

EXPENSE
Does skipping the conjunctival incision and sclerotomy sutures lower costs? No. The SGV packs are about 15% more expensive, even when the cost of sutures is subtracted.

SURGICAL SPEED
With SGV, the removal of vitreous is slightly slower, but opening and closing the conjunctiva and sclerotomies is faster.^4,15,16 I have studied a few consecutive cases and found that the opening and closing time averages approximately 7.5 minutes for a 20-gauge case. Even the placement and removal of the cannula and tamponade time at the sclerotomy for SGV takes at least 2.5 minutes. Thus, the maximum potential time saved is 5 minutes, discounting the longer vitreousremoval stage. to the ASRS 2010 Preferences and Trends Survey, 70% of respondents sometimes needed closure, whereas around 13% needed closure more than 25% of the time.² Moreover, with SGV, the scrub nurse must complete more steps before the surgeon’s part begins, thus lengthening the effective turnover time for the ophthalmologist. 5,16 The minimal time saved by SGV therefore may not add up at the end of the day.

DOWNSIDE
A potential disadvantage of SGV is that it can compromise the examination of the peripheral fundus because of the trocar/plug unit’s high profile. Furthermore, instrumentation has not been fully reproduced. For example, I have not found a comfortable SGV internal limiting membrane peeling counterpart to the barbed 20-gauge microvitreoretinal blade.

CONCLUSION
None of the metrics identified herein definitively favor SGV. Instead, some support standard 20-gauge instrumentation. Nevertheless, surgeons’ use of SGV is clearly increasing. Is this due to marketing or actual performance? ¹⁷ Embracing a system because of what you can get away with, rather than what works best, is an important paradigm to evaluate. Instruments’ size is probably an overrated issue. Good results are obtainable with either system, and surgeons should feel free to govern themselves in a way that makes them most comfortable and confident of the result.

William E. Smiddy, MD, is a professor of ophthalmology at the Bascom Palmer Eye, University of Miami Miller School of Medicine, in Florida. Dr. Smiddy may be reached at (305) 326-6172; wsmiddy@med.miami.edu.

1. American Society of Retina Specialists.ASRS 2010 Preferences and Trends Survey. http://www.asrs.org/home/communicate_and_educate/pat_survey/2010.
2. Gupta OP,Weichel ED,Regillo CD,et al.Postoperative complications associated with 25-gauge pars plana vitrectomy. Ophthalmic Surg Lasers Imaging. 2007;38(4):270-275.
3. Rizzo S,Belting C,Genovesi-Ebert F,diBartolo E.Incidence of retinal detachment after small-incision,sutureless pars plana vitrectomy compared with conventional 20-gauge vitrectomy in macular hole and epiretinal membrane surgery.Retina.2010;30:1065-1071.
4. Kadonosono K,Yamakawa T,Uchio E,et al.Comparison of visual function after epiretinal membrane removal by 20-gauge and 25-gauge vitrectomy.Am J Ophthalmol.2006;142:513-515.
5. Rizzo S,Genovesi-Ebert F,Murri S,et al.25-gauge,sutureless vitrectomy and standard 20-gauge pars plana vitrectomy in idiopathic epiretinal membrane surgery:a comparative pilot study.Graefes Arch Clin Exp Ophthalmol.2006;244:472-479.
6. Wimpissinger B,Kellner L,Brannath W,et al.23-gauge versus 20-gauge system for pars plana vitrectomy:a prospective randomized clinical trial.Br J Ophthalmol.2009;93:1694-1695.
7. Scott IU,Flynn HW Jr,Dev S,et al.Endophthalmitis after 25-gauge and 20-gauge pars plana vitrectomy:incidence and outcomes.Retina.2008;28:138-142.
8. Kunimoto DY,Kaiser RS.Incidence of endophthalmitis after 20- and 25-gauge vitrectomy.Ophthalmology. 2007;114:2133-2137.
9. Shaikh S,Ho S,Richmond PP,et al.Untoward outcomes in 25-gauge versus 20-gauge vitreoretinal surgery.Retina. 2007;27:1048-1053.
10. Amato JE,Akduman L.Incidence of complications in 25-gauge transconjunctival sutureless vitrectomy based on the surgical indications.Ophthalmic Surg Lasers Imaging.2007;38:100-102.
11. Chieh JJ,Rogers AH,Wiegand TW,et al.Short-term safety of 23-gauge single-step transconjunctival vitrectomy surgery.Retina.2009;29:1486-1490.
12. Nam DH,Ku M,Sohn HJ,Lee DY.Minimal fluid-air exchange in combined 23-gauge sutureless vitrectomy,phacoemulsification, and intraocular lens implantation.Retina.2010;30:125-130.
13. . Mason JO,III,Yunker JJ,Vail RS,et al.Incidence of endophthalmitis following 20-gauge and 25-gauge vitrectomy. Retina.2008;28:1352-1354.
14. Shimada H,Nakashizuka H,Takayuki H,et al.Incidence of endophthalmitis after 20- and 25-gauge vitrectomy. Ophthalmology.2008;115:2215-2220.
15. Parolini B,Ramanelli F,Prigione G,Pertile G.Incidence of endophthalmitis in a large series of 23-gauge and 20- gauge transconjunctival pars plana vitrectomy.Graefes Arch Clin Exp Ophthalmol.2009;247:895-898.
16. Kellner L,Wimpissinger B,Stolba U,et al.25-gauge vs 20-gauge system for pars plana vitrectomy:a prospective randomised clinical trial.Br J Ophthalmol.2007;91:945-948.
17. Lewis H.Sutureless microincision vitrectomy surgery:unclear benefit,uncertain safety.Am J Ophthalmol. 2007;144:613-615.

Twenty-five–gauge cutters offer distinct advantages and represent the most current technology available.
STEVE CHARLES, MD

When De Juan and his colleagues introduced the 25-gauge, sutureless, transconjunctival vitrectomy,1 its advantages were said to be a more comfortable eye, less inflammation, reduced operating times, faster visual recovery, and abstract concepts such as a “minimally invasive” procedure. In addition, some surgeons touted the technique for in-office vitrectomy—in my opinion, a bad idea then and now. All of the procedure’s advantages have been validated except in—office surgery. Its indications have expanded to include all vitrectomy cases, except when one wound must be enlarged to 20 gauge for the removal of intraocular foreign bodies or to accommodate the fragmenter for the removal of dense nuclear material in the scenario of dislocated lenticular material.

INITIAL SKEPTICISM
Like many other surgeons, I doubted that, with this technique, I would be able to remove the dense epiretinal membranes seen in cases of diabetic traction retinal detachments or dense vitreous hemorrhages. I soon learned that 25-gauge cutters were up to the task and actually offered advantages over 20-gauge or even 23-gauge instruments. Smaller cutters facilitate greater lateral access to epiretinal membranes because of their small outside diameter.

Many surgeons and companies have stated that 25-gauge cutters produce insufficient flow rates, an assertion that has proven untrue with appropriate vacuum levels. I use proportional vacuum with a maximum setting of 650 mm Hg. I have always used 45-mm Hg infusion except in children and rare patients with very low perfusion pressure during surgery under general anesthesia. I find that this setting combined with new, low-resistance infusion cannulas always produces sufficient infusion. The IOP Compensation feature of the Constellation Vision System (Alcon Laboratories, Inc., Fort Worth, TX) adds another layer of protection against low IOP.

THE TECHNIQUES COMPARED
I coined the term port-based flow limiting as a contrast to the console-based flow control usually produced by peristaltic pumps. Port-based flow limiting is created by smaller-diameter cutters and higher cutting rates. The Constellation platform’s Ultravit High Speed Vitrectomy Probes currently produce 5,000 cuts/min. Console-based flow control is slower than port-based flow limiting, because fluidic signals must travel through 7 feet of elastomeric tubing to the console before pressure sensors can detect the signal, process it, and actuate valves to send the response back down the long tubing.

Because flow resistance is proportional to the fourth power on the diameter, 20-gauge systems produce much more pulsatile vitreoretinal traction than 25-gauge vitrectomy systems. In addition, 20-gauge cutters produce much more surge after sudden elastic deformation of dense tissue through the port, thereby increasing the rate of iatrogenic retinal breaks. This is directly analogous to reduction in surge after a break in phaco occlusion when Alcon Laboratories, Inc., introduced the MicroFlare ABS and MicroTaper ABS phaco tips. Today’s high-vacuum, low-flow phacoemulsification keeps the anterior chamber more stable, similar to the reduced pulsatile vitreoretinal traction with 25-gauge cutters and high cutting rates.

Anterior vitrectomy for vitreous loss during cataract surgery requires the highest possible cutting rates and the lowest effective vacuum or flow rate, because the anterior vitreous is in close proximity to the vitreous base. The vitreous base is the zone of greatest vitreoretinal adherence, and the retina at the vitreous base is approximately 1/100 the tensile strength of the retina near the optic nerve.

CONCLUSION
Many surgeons still using 20-gauge technology assert that it is the gold standard, a monetary rather than a medical concept. In my view, these ophthalmologists are not using the most current technology. I perform a 25-gauge, sutureless, transconjunctival vitrectomy, except when I must enlarge one sclerotomy for intraocular foreign bodies or dense dislocated lenticular material. I recommend using a 23-gauge cutter for anterior vitrectomy using topical anesthesia, because saccades can cause 25-gauge tools to flex excessively.

Steve Charles, MD, is a clinical professor of ophthalmology at the University of Tennessee in Nashville, and he is an adjunct professor of ophthalmology at Columbia College of Physicians & Surgeons in New York. Dr. Charles is also an adjunct professor of ophthalmology at the Chinese University of Hong Kong. He is a consultant to Alcon Laboratories, Inc. Dr. Charles may be reached at (901) 767-4499; scharles@att.net.

1. Fujii GY,De Juan E Jr,Humayun MS,et al.A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery.Ophthalmology.2002;109(10):1807-1812.