Microincisional Vitrectomy: Techniques, Tips and the Future

A report on the impact of wound construction on successful transconjunctival vitrectomy

Microincisional Vitrectomy: Techniques, Tips and the Future

A report on the impact of wound construction on successful transconjunctival vitrectomy.


Major advances in technology for anterior and posterior segment surgery have brought about a dramatic change in the landscape of ophthalmology over the past 2 decades. Following the success of sutureless clear cornea cataract incisions, with the benefits of decreased operative time, faster visual recovery and decreased corneal astigmatism, posterior segment surgeons have developed sutureless microincision vitrectomy systems.

Nonsutured sclerotomy wounds are much smaller than the clear cornea cataract incisions made with 3.5 mm to 4.0 mm keratomes. As a comparison, a traditional 20-g wound is approximately 1.1 mm, and microincision wounds are even smaller — 0.72 mm and 0.5 mm for 23-g and 25-g incisions, respectively. In this report, we review the history of microincision surgery and provide some tips for performing sutureless microincisional vitrectomy.


Since Chen first described sutureless vitrectomy in 1996,1 many reports and variations on sutureless sclerotomies have emerged.2-4 A lack of adequate studies, however, combined with concerns about complications have prevented wide adoption by vitreoretinal surgeons. A major advance in instrumentation in 2002 paved the way to our current utilization of microincision surgery.5,6

In microincision vitrectomy, sclerotomies are made through the conjunctiva with no conjunctival suturing required at the completion of surgery, owing to the small size and presumed self-sealing characteristics of the wound. Reportedly, this technique has led to reduced operating times, faster healing times, quicker visual recovery and improved comfort for patients.7-12 For these reasons, the popularity of sutureless, transconjunctival microincision vitrectomy has exploded among vitreoretinal surgeons. This is evident from the increasing number of publications (Figure 1), as well as the 2007 Practice and Trends (PAT) survey of the American Society of Retina Specialists, in which 47% of respondents reported they use 23-g or 25-g systems in the majority of their cases, and at least 75% use these systems in some of their cases.13

Mehran Taban, MD, is a vitreoretinal fellow at the Cleveland Clinic Foundation at the Cole Eye Institute.

Peter K. Kaiser, MD, practices at the Cleveland Clinic Foundation at the Cole Eye Institute. Dr. Kaiser receives research grant support and is a consultant for Alcon.


Along with increasing popularity, questions and concerns similar to those associated with sutureless cataract surgery have been raised about the self-sealing properties of sutureless sclerotomies. Opponents of the procedure point to a greater risk of hypotony and endophthalmitis based on a handful of studies that compare endophthalmitis rates after sutureless versus conventional vitrectomy.14-24

The largest study reported an endophthalmitis rate of 0.018% (1/5, 498) following 20-g surgery and 0.23% (7/3, 103) following 25-g sutureless vitrectomy.16 Similarly, Shaikh and colleagues reported a rate of 0.0% (0/129) with 20-g and 1.6% (2/129) with 25-g,17 and Scott and colleagues noted a rate of 0.03% (2/6, 375) with 20-g and 0.84% (11/1, 307) with 25-g sutureless vitrectomy.21 Data combined from these studies indicate the rate of endophthalmitis after 20-g surgery was 0.025% (3/12, 002); after 25-g sutureless vitrectomy, it was 0.45% (20/4, 410).

Traditionally, endophthalmitis rates after 20-g vitrectomy have been reported between 0.03% and 0.05%.25-27 Thus, the rate with sutureless surgery in these early reports does appear to be greater. In fact, in the 2007 PAT survey, 14.7% of respondents stated they had a case of endophthalmitis after 25-g or 23-g vitrectomy. Therefore, it is difficult to dispute the fact that the endophthalmitis rate is higher with sutureless 25-g vitrectomy compared with conventional 20-g sutured vitrectomy. The question remains: Why? The answer may be related to wound construction.

Kunimoto and Kaiser stated that incisions were not beveled in their series,16 while in the series by Scott and colleagues, 73% of the endophthalmitis cases were from straight incisions.21 Moreover, there have been reports of higher hypotony rates associated with sutureless vitrectomy using straight incisions.18-20 In a more recent study, Mason and colleagues reported an endophthalmitis rate of only 0.053% following 25-g vitrectomy, compared with 0.076% after 20-g. Interestingly, they used angled sclerotomies in their 25-g series.28 Thus, wound construction appears to be vital.


Ultrasound biomicroscopy (UBM) has been used to evaluate wound architecture after microincision surgery, but its utility is limited for several reasons. The resolution of UBM is poor for imaging small areas, such as sclerotomy sites; it also uses a contact immersion methodology, which is inappropriate immediately following surgery.29-34 Furthermore, until recently, there were no dynamic real-time studies of wound behavior immediately after microincision surgery when wounds are not yet healed.

Oblique or angled incisions are believed to help decrease or prevent wound leakage because intraocular pressure causes their internal lip to press against the outer lip, thereby aiding wound closure.35-37 The importance of creating oblique incisions as opposed to straight incisions has been highlighted in several recent in vitro studies where angled incisions were found to be superior when evaluated grossly, histopathologically and with anterior segment OCT.38-40 Singh and colleagues demonstrated ingress of ocular surface fluid (India ink) into sutureless straight incisions following 25-g vitrectomy in cadaver human globes.38

Recently, we investigated the dynamic morphology and integrity of sutureless vitrectomy wounds (23-g and 25-g) in cadaver rabbit eyes using anterior spectral domain optical coherence tomography (OCT) and histologic analysis with India ink.39 Anterior spectral domain OCT revealed that straight incisions gaped considerably more than oblique incisions.

It also demonstrated open wounds with straight incisions under all IOP conditions, with a slightly larger wound width under high IOP conditions. In contrast, oblique incisions demonstrated less wound gape overall.39 Histologic analysis of the wounds showed penetration of India ink along the length of all straight incisions. In contrast, no India ink particles were observed along the length of oblique incisions.39 This indicates the potential for surface fluid inflow through straight incisions before wound healing or closure. These findings are similar to those observed with sutureless clear cornea cataract incisions.41-43

Using the Visante anterior segment OCT (Carl Zeiss Meditec, Dublin, Calif.), we also evaluated the in vivo dynamic (real time) wound closure characteristics of angled 23-g sutureless sclerotomies following vitrectomy on human eyes.40 The in vivo study showed that, although external partial gaps are observed on postoperative day 1, the wounds are closed. On postoperative day 8, essentially no evidence of gaping is seen on anterior segment OCT. These scans demonstrate that 23-g sutureless vitrectomy using oblique (angled) incisions appears to provide adequate wound closure, which is evident even on postoperative day 1.40

In terms of the reported higher endophthalmitis rates, these investigations have several implications. First, they suggest that oblique incisions provide better wound apposition and stability compared with straight incisions, regardless of the gauge of microincision surgery. Second, similar to cataract surgeons, vitreoretinal surgeons need to pay careful attention when creating sclerotomy incisions to avoid wound leakage. Moreover, they should carefully evaluate the state of the wounds at the completion of surgery and evaluate for signs of gaping or leakage. If there is any question with regard to the self-sealing characteristics following surgery (eg, continued leakage), surgeons should not hesitate to place a suture, even if they thought they had created a self-sealing incision initially.

Schematic of wound construction for an angled (tunnel, bevel) sclerotomy. The eye is penetrated as tangentially as possible parallel to the limbus with the bevel up. Once past the trocar sleeve, the angle is changed to 90° (perpendicular to surface).

Technique of removing the cannula to avoid vitreous wick: place a hard instrument (eg, light pipe) and pull up on the cannula.

Leakage could occur because the incision was not truly beveled to begin with or because significant manipulation of the sclerotomies during surgery changed the wound architecture. In early cases, the desire to avoid sutures may have biased the surgeons to not use them when they were required. The bottom line is that the essence of successful transconjunctival vitrectomy lies in careful wound construction and its evaluation at the completion of surgery. See "Key Tips for Microincisional Vitrectomy," which summarizes some key points about sutureless microincision vitrectomy that might be useful in your clinical practice.


Since its introduction in 2002, the instrumentation and technology for microincision surgery has seen many changes and improvements.5,6 The next several years will surely bring about more advancements to answer the challenges that face this field, including improved lighting, less flexible instruments and more efficient small-gauge cutters, among others. One of the exciting new technologies is the CONSTELLATION® Vision System with 23- and 25-g cutters that offer 5000 cuts per minute and surgeon selected duty cycle control. The combination of high cut rate and the ability to vary the duty cycle lets surgeons have very high flow rates when performing a core vitrectomy, then by increasing the port closed time by varying the duty cycle, precise and safe shaving of the vitreous can be completed when in the periphery or near mobile retina. Unlike older microincision cutters, these new cutters offer the ideal combination of efficient vitreous removal with increased safety.

With regard to wound closure, other than careful wound construction and evaluation, recently described techniques, such as those using a releasable suture and tissue glue, can help avoid the wound leakage that may occur in some cases despite an angled incision.44-46 These techniques can potentially be used selectively on a case-by-case basis if a surgeon is unsure about the integrity of the wound at the completion of the surgery. In addition, design changes are being implemented to improve the blades used to insert the small-gauge cannulas. These improvements are intended to further decrease the number of cases of leakage and improve the outcomes of MIVS cases. Future studies should also help elucidate the potential effect of a fluid-filled eye versus an air/gas-filled eye on wounds and sclerotomy tamponade internally. It remains to be seen if other wound sizes (eg, 27-g) will have a role in microincision vitrectomy.

Key Tips for Microincisional Vitrectomy
Wound type: Angled (bevel) sclerotomy preferred over straight incision.

Wound creation
a) displace the conjunctiva over the wound entry site
b) flatten the sclera during wound creation to provide the longest wound possible, which should help provide best wound apposition

End of surgery
a) perform partial air-fluid exchange
b) remove cannula with a hard/solid instrument (eg, light pipe) to prevent vitreous wick
c) massage the wound with a cotton-tipped swab
d) allow time for leakage to stop, if there is any
e) if unsure about leakage, place a suture
f) straight incision requires a suture


In terms of a major advancements in vitreoretinal technology, the introduction and increasing adoption of sutureless microincision vitrectomy surgery parallels the introduction of pars plana vitrectomy systems some 30 years ago. While we appreciate its benefits, we must be aware that only careful and systematic evaluation of the best techniques will provide the safest and most efficient outcomes. The findings of recent in vitro and in vivo studies demonstrate that oblique (angled, beveled) incisions are superior to straight incisions because they provide better wound apposition and stability.38-40 The importance of wound construction and its dynamic state cannot be overstated. Vitreoretinal surgeons should be aware of these factors when constructing their wounds and evaluating them postoperatively to minimize the risk of wound gaping, leakage and endophthalmitis, as has been proposed and followed for sutureless clear cornea incisions.41-43 RP


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