Evolutions in vitreoretinal surgery have focused on improvements in surgical instrumentation, viewing systems, illumination, and adjunctive agents for tissue manipulation. The advent of advanced microincision vitrectomy surgery (MIVS) has heralded an era of enhanced surgical access and improved patient outcomes. Limitations in MIVS have focused on issues with instrumentation, including transconjunctival cannulation systems, vitrectomy cutters and limited functionality and array of instruments (forceps, scissors, pics, light pipes). Nonetheless, MIVS offers benefits for both patients and surgeons, and today's 23-gauge and 25-gauge instruments are approaching the full functionality of 20-gauge instrumentation, making the surgical transition from 20 gauge to MIVS easier. Further, recent advances in instrument manufacturing have made most instruments required for MIVS available in an individually packaged, disposable form, making the procedure safer by providing a single-use, sterile configuration that prevents instrument damage from reuse from impacting surgical precision.

PREVIOUS SHORTCOMINGS IN INSTRUMENTATION
Initially, when surgeons were considering transitioning from standard 20-gauge surgery to either 23- or 25-gauge surgery with the transconjunctival microincisional approach, the quality of the instruments and the breadth of instrumentation were very limited. For example, we did not have access to our accustomed array of forceps, we were limited in endoilluminator and laser probe designs, and typical scissors either functioned poorly or were unavailable. Additionally, particularly with the 25-gauge instrumentation, the flexibility of the different instruments was a significant compromise. The instruments handled very differently from standard 20-gauge instruments. With previous 25-gauge instrumentation, the instrumentation would flex during surgery. In fact, it would often flex in a contrary direction, so if the surgeon wanted to go to the right, the instrument would flex to the left. That was unexpected, because surgeons had never seen instruments behave like that before. In my practice, concerns with limitations in instrument performance excluded adoption of 25-gauge surgery in virtually all patients.

Alternatively, because 23-gauge instruments handle similarly to 20-gauge instruments, many surgeons initially preferred 23-gauge surgery. Issues with 23-gauge surgery focused not on instruments but on wound construction (something within the surgeon's ability to control) enabling early adoption and easier transition. Today, there is a disposable instrument available in 23- and 25-gauge that is identical in function to virtually every 20-gauge instrument that has previously been available, greatly facilitating the surgeon's transition to microincision surgery.

MAKING THE TRANSITION
With 23-gauge MIVS, the intraocular surgical management including vitrectomy, illumination, membrane removal, drainage, and laser are indistinguishable from standard 20-gauge surgery. The surgical event that requires transition is the introduction and stabilization of the transconjunctival trocars. The learning curve is in establishing a comfort level of placing the 23-gauge trocars into the eye in a stable and safe manner so that wound construction is associated with wound closure and trocar removal. With 20-gauge systems, surgeons entered the eye with a straight, direct incision. This worked well, but as surgeons converted to 23- and 25-gauge systems, they found that many of these wounds would not close spontaneously. Recent data have shown that an oblique entry, allowing secure trocar placement, establishes a stable closed sclerotomy with trocar removal and is best for both 23- and 25-gauge procedures. Alcon Laboratories, Inc. (Fort Worth, TX) has developed microincisional trocar/cannula systems in both 23- and 25-gauge that provide a single-step entry into the eye. Significant advances in the next generation of trocar blade design has improved wound construction and closure (Figure 1).

Transitioning to 25-gauge surgery has become easier with the introduction of next generation microincisional instrumentation. Trocar entry is best approached through an oblique entry for 25-gauge cannula placement, though this step is not as critical as for 23-gauge MIVS procedures.

Limitations to transitioning to 25-gauge MIVS surgery were clearly associated with instrument concerns as opposed to transconjunctival wound construction. Current advances in the new 25+ gauge instruments were targeted at concerns that focused on instrument stability, surgical field illumination and increased armamentarium of forceps, pics and scissors. These next generation instruments significantly reduces inappropriate flexibility utilizing targeted manufacturing techniques, improved instrument design and enhanced materials when compared with the previous 25-gauge instruments. The 25+-gauge instrument design has moved these instruments within the surgical standard for 20-gauge instruments (Figure 2).

Along with instrument improvements, the new 23- and 25-gauge vitrector design has improved immensely, too. The port on the 25-gauge Alcon vitrectomy probe has been moved closer to the distal tip (similar to the 23-gauge version; Figure 3), and coupled with a dual pneumatic actuator and improved flow control, both the 23- and 25-gauge vitrectors will achieve 5,000 cpm with outstanding flow characteristics. Additionally, the 25+-gauge vitrector has increased probe stiffness and flow improvements as integral to the new design.

THE BENEFITS OF DISPOSABLES
Another major improvement is the introduction of disposable instruments. Historically, we have not used disposable instruments in 20-gauge surgery. However, microinstruments have presented new challenges. In addition to the issues of sterilizing and storing the instruments, 23- and 25-gauge instruments are more likely to be damaged than 20-gauge instruments due to increased fragility. At Bascom Palmer Eye Institute (Palm Beach Gardens, FL), we experienced that the incidence of damage to these instruments may be as high as 30% over a period of 10 deployments. Additionally, for high-volume practices, there is a significant cost to maintain reusable microinstruments. At Bascom Palmer, we maintain a fully staffed clean room, sterilize our instruments, and stock multiple backup instruments in case a particular instrument is not functional at the time of use. Ultimately, we engender additional expense related to damaged instruments requiring out-sourcing for repair (Figure 4).

Disposables have been rapidly integrated into most clinical practices for 23- and 25-gauge surgery. As difficult as it is to maintain reusable 20-gauge instruments, it is even more difficult to maintain 23- and 25-gauge instruments because they are smaller, less stable, and more easily damaged during normal processing and handling. Cost is also an issue. For example, a typical cost of a non-disposable forceps can range from $2,000 to $3,500. The requirement to purchase two or three backups of every instrument means that a practice could have instrument stock in the $20,000 to $50,000 range.

There is also the concern that reusable instruments could be contaminated with prions and/or not properly sterilized with standard techniques. This concern, addressed in a review in Retina Times has not been supported with clinical concerns over the last decade. Nonetheless, with disposable instrumentation, sterilization compliance is never an issue. Finally, there have been some concerns and an evolution in terms of sterilization requirements from the Joint Commission on Allied Hospitals. The concept of flash sterilization is no longer acceptable; full sterilization cycles are necessary. This means that surgeons may need multiple instruments sets that can be sterilized in a standard, non-flash manner.

With disposables, although a new instrument must be purchased for each procedure, they are sterile-packaged, readily available, and both effective and functional. Additionally, there is no concern of damaging the instrument during the procedure. No back-up instrumentation is required, and surgeons have access to have a wider spectrum of instruments. In other words, you can have a broader range of disposables available at a much lower facility cost. Initial limitations in the armamentarium of disposable 23- and 25-gauge instruments have now been eliminated. In my opinion, Alcon has essentially every major instrument including forceps, scissors, backflush and pics in a disposable format for both 23- and 25-gauge procedures (Figure 5).

SUMMARY
In conclusion, advances in disposable MIVS instruments have advanced microsurgical management of the patient with both relatively simple and complex vitreoretinal pathology. I have compiled a list of some of the reasons that I use disposable instrumentation in Table 1.

These instruments potentially improve surgical management (elimination of damaged instruments) and patient safety (elimination of reprocessing compliance issues). These instruments are unique in that they are new at the beginning of each procedure. Finally, there is no concern of performance issues related to compromise of the instrument over time while the quality of the disposable instruments has achieved an exemplary standard. In the past, surgeons have been concerned that disposable instruments were not available in the range of instruments necessary to manage complex retinal pathology, did not meet quality standards comparable with non-disposables, and were prohibitively expensive to be utilized in routine surgery. These are clearly concerns of the past with the delivery of next generation disposable instruments that are reliable, precision-crafted, compliant and convenient and deliver to the surgeon and the patient the best instrumentation for microincisional vitrectomy surgery.

Timothy G. Murray, MD, FACS, is Professor of Ophthalmology and Radiation Oncology at the Bascom Palmer Eye Institute at the University of Miami Miller School of Medicine in Florida. Dr. Murray reports that his is is a Consultant for Alcon Laboratories, Inc., and a member of the Alcon Retina Advisory Council. He can be reached via e-mail at tmurray@med.miami.edu.