Pertinent Issues in Vitrectomy Surgery
COORDINATED BY ABDHISH R. BHAVSAR, MD
Welcome to Face Off, a column that explores controversial topics in the diagnosis and management of retinal diseases. Our typical format has involved covering several topics in each issue with one retina specialist voicing one line of thought in favor of the treatment or surgery and another retina specialist voicing an opposing line of thought. This column should be held in the spirit of a debate society. We do not advocate that you adopt these specific lines of thought, rather we hope this provides you with insight into how some retina specialists view these issues, with the desire that this will engage your thought process.
In this issue, we will explore 23-g vs 25-g vitrectomy surgery and the use of disposable vs reusable instruments in vitreous surgery.
PRO 25-g SURGERY
I perform most vitrectomies with a 25-g system, and prefer to insert the cannulas so that they are aimed toward the pathology. Therefore, they are often pointed toward the macula and are inserted tangential to the scleral surface (ie, a straight incision). Experience, as well as independent experimental studies, has demonstrated that this technique results in a nicely healed, watertight wound in virtually all cases.
Some surgeons recommend an oblique entry, a technique that I reserve for eyes with peripheral or anterior pathology, or for eyes with thin sclera (to lengthen the wound and decrease the chance of leakage). Is an oblique entry necessary in every 25-g case? I dont think so, but surgeons using a 25-g system are free to choose.
For those using a 23-g system, an oblique incision isnt an option its a requirement. With 23-g systems, avoidance of a postoperative wound leak is highly dependent upon an oblique entry angle and a long internal scleral wound. This means that cannulas are rarely aimed toward the pathology and that the instruments must torque the sclerotomies during most of the case.
Each of the differing gauge vitrectomy systems has its strengths. The expectation of a watertight wound, independent of entry angle, is a real advantage of 25-g vitrectomy systems.
PRO 23-g ANGLED INCISIONS
While sutureless transconjunctival vitrectomy has been a major advance in vitreoretinal surgery, wound construction remains an important consideration in choosing between 20-, 23-, and 25-g systems as well as whether to create straight, angled, or beveled incisions. Inadequate wound closure is a significant risk for hypotony, vitreal incarceration, suprachoroidal hemorrhage, and endophthalmitis.1,2
Several published series suggest a relatively high (5% to 14%) rate of hypotony or suture closure with 25-g systems, due to the roughly 0.5 mm round hole left in the sclera from stretching the wound with the 25-g trocar, which is shaped like a hypodermic needle.3,4,5
In contrast, 23-g surgery utilizing a stiletto-type blade forms a roughly 0.72 mm slit-like opening6 in an angled fashion, with less stretching of the sclera. Intraocular pressure helps to close the tunnel and a recent series suggests a much lower rate of hypotony or suture closure than with 25-g surgery.7 Recent animal studies demonstrated histologically that the 2-step 23-g insertion system results in a well constructed, highly reproducible wound without tissue flaps or avulsion, which was not the case with other insertion methods.8
We currently employ a second-generation, single step, 23-g trocar-cannula system with valve caps that prevent fluid efflux through the cannulae when changing instruments. The 23-g system employs stiff, robust instruments, quite similar to 20-g systems, and can be easily used with silicone oil.
FOR THE USE OF REUSABLE INSTRUMENTS
Today, we have high-quality small-gauge disposable intravitreal forceps, softtipped needles, Xenon fiberoptics, and endolaser probes as well as high-speed vitrectomy cutters. The risk of contamination and malfunction may be reduced by the use of disposable instrumentation. While it makes sense to dispose of certain instruments, other instruments such as forceps, specula, and indirect lenses remain as good options for reusable items. Disposables have markedly improved in recent years but reusable instruments are precise, sturdy, and reliable.
PRO DISPOSABLE VITRECTOMY INSTRUMENTATION
The use of disposable vitrectomy instruments has been an evolution in quality, production efficiency and affordability. This has been particularly true in the case of 25-g instrumentation. The Grieshaber 25-g end-closing forceps (Alcon, Fort Worth, Texas) in particular has become my preferred instrument for internal limiting membrane (ILM) peeling, removal of proliferative vitreoretinopathy membranes, and even for peeling epiretinal membranes under silicone oil. The fluidics of the 25-g cutter are superior and afford the surgeon a precise level of control. Current disposable 25-g cutters, forceps, scissors, endoilluminators, endolasers, and trochars are very functional and well constructed. Similar advances have been made with 23- and 20-g systems.
25-g instruments are delicate, and if not handled carefully can easily be rendered useless. If reusable, these instruments dont hold up well to repeated handling and sterilization. As many operating rooms no longer flash instruments, the sterilization turnaround time is now much longer. ORs need to have at least 5 or 6 reusable instruments on hand, which is a major capital investment.
The cost of a reusable forceps is about $2500 and the cost of a disposable instrument $125. One could purchase 20 disposable forceps for the cost of a single reusable forceps. There is time and material cost in the reprocessing and sterilization of instruments and an inherent lack of efficiency, issues avoided by the use of disposables.
On a final note, prions, which are difficult to detect and remove through sterilization and although quite rare, could cause diseases such as transmissible spongiform encephalopathies.
The many non-disposable forceps, scissors, and picks that I have purchased over the years are usually stored in their boxes and with the exception of the large foreign-body forceps, rarely used. RP
|Abdhish R. Bhavsar, MD, is an attending retina surgeon at the Phillips Eye Institute, director of clinical research at the Retina Center, PA, in Minneapolis, and adjunct assistant professor at the University of Minnesota. E-mail him about Face Off at email@example.com.|
5. Gupta A, Gonzales CR, Lee SY, Freeman JY, Estafanous MF, Kreiger AE, Schwartz SD. Transient Post-Operative Hypotony Following Transconjunctival 25 Gauge Vitrectomy. Invest Ophthalmol Vis Sci. abstract 2026, 2003.