Since its introduction less than a decade ago, microincision vitreoretinal surgery (MIVS) has been rapidly adopted in the retina community. Sutureless MIVS techniques and technology were created with the goal of providing a less invasive, yet still effective alternative to traditional 20-gauge technology for performing vitrectomy.
The first MIVS systems incorporated 25-gauge instrumentation. However, as surgeons gained experience with the early 25-gauge technology, they reported problems with the flexibility of the instruments and a resultant increased surgical complexity in anterior vitreous dissection. This led to the development of 23-gauge instrumentation, 1-7 representing a compromise in size between 20 and 25 gauge.
With the larger incision size needed to introduce 23- gauge instruments, wound construction becomes an important consideration. Achieving and maintaining adequate wound closure are key factors in the success and the utility of 23-gauge instrumentation.
COMPARATIVE STUDY
To assess the role of incision type on wound stability
and construction in 23-gauge vitrectomy, we performed
an interventional, comparative, retrospective study of
wound performance to evaluate the wound characteristics
and stability of a single-step 23-gauge incision (Figure
1) compared with a two-step incision (Figure 2).8
In a retrospective review, eyes undergoing 23-gauge vitrectomy with any one of three available platforms for cannula insertion were identified. Exclusion criteria included previous vitreous surgery, a known history of scleritis, or a history of glaucoma surgery or hypotony. Patients in both groups were pretreated with a fourth generation quinolone and prepped with the application of povidone-iodine solution directly to the ocular surface. All patients underwent standard three-port vitrectomy. No additional incision was made to perform a bimanual technique, so all study eyes were limited to only three incisions.
Outcome measures included the need to secure the wound postoperatively, postoperative intraocular pressure (IOP), and complications.
CANNULA INSERTION
The conjunctiva was displaced anteriorly before cannula
insertion.
With the two-step system (Dutch Ophthalmic USA, Exeter, NH), the cannula was inserted after creation of an incision using an angled, flat microvitreoretinal (MVR) stiletto blade. The angled blade created a reproducible 15° wound, in part because of the angle and sharpness of the blade.
The single-step system (Alcon, Fort Worth, TX) cannula was inserted in a single pass on an angle that varied between 15° and 30°. The variation was due, in part, to the straight blade and cyclotorsion of the globe during insertion.
No difficulty with cannula insertion was noted regardless of which platform was used.
RESULTS
Included in the study were 284 eyes of 271 patients;
162 eyes were treated using the two-step system and
122 patients using the single-step system.
The underlying retinal pathologies for both treatment groups were similar (Table 1). The most common diagnoses were vitreous hemorrhage, retinal detachment, and macular hole, with numbers about equal in each group. Mean follow-up was 6.8 months. Mean age of the patients was 68.3 years, and there were slightly more women than men (51.8% vs 48.2%).
Twenty-nine (23.8%) eyes in the single-step group vs six (3.7%) eyes in the two-step group required a suture to secure the wound at the end of surgery (P=.002). Of the eyes requiring a suture, two in the two-step group and 13 in the single-step group needed multiple wounds sutured.
Chemosis on postoperative day 1 was present in nine eyes in the single-step group and four eyes in the twostep group that did not require sutures.
Complications occurred in 10 patients (6.17%) in the two-step group and seven patients (5.73%) in the singlestep group. This difference was not statistically significant. The most frequent complication, vitreous hemorrhage, occurred more often in the two-step group (Figure 3 [graph, slide 10]). One eye in the single-step group developed endophthalmitis.
Mean preoperative IOP was 17.8 mm Hg. Of the patients not requiring a secondary intervention, eyes in the single-step group had a mean IOP of 15.1 mm Hg at 1 day postop, compared with a mean IOP of 16.9 mm Hg in eyes in the two-step group. This difference was not statistically significant. Hypotony, defined as IOP of 5 mm Hg or less, occurred in 11 eyes in the single-step group and two eyes in the two-step group. Patients requiring wound closure had a mean postop IOP of 17.1 mm Hg.
DISCUSSION
The MVR blade used in the two-step technique creates
a flat, linear, self-sealing incision that appears to be
stable despite surgical manipulation. Little leakage at the
entry site is noted after manipulation of the cannula. By
contrast, the one-step incision after manipulation forms a chevron-type incision that appears to be more prone
to wound gape and leakage from the wound. These incisions
appear to have less stability with surgical manipulation
and to require stabilization postoperatively.
Eyes in the single-step group required suture closure more frequently than those in the two-step group, and this difference was statistically significant (P=.002).
The overall complication rate (5.98%) was low for all patients, and there was no statistical difference in the complication rates between the groups. The most frequent postop complication was vitreous hemorrhage. One eye in this series developed endophthalmitis.
Both types of 23-gauge system allow the performance of safe, easy, and efficient retinal surgery. In this series, the two-step system required suture closure significantly less often than the single-step system.
The difference in rates of inadequate wound closure between the two cannula systems may be related to wound construction and blade design. The stiletto-type design of the MVR blade seems to create a sharper and more controlled incision. In addition, the use of the angled blade with the two-step cannula system may offer the advantage of reproducibility when compared with a single-step system with which the angle of entry may vary.
While in this series the complication rates were similar in the two groups, surgeons must be vigilant of potential complications, in particular hemorrhage and infection, associated with inadequate wound closure in MIVS.
Keith A. Warren, MD, is a professor of ophthalmology at the University of Kansas and founder of Warren Retina Associates, PA, in Overland Park, KS. Dr. Warren states that he serves as a consultant and speaker for Alcon, Dutch Ophthalmic, and Genentech. He may be reached at +1 913 339 6970; fax: +1 913 339 6974; or via e-mail at kwarren@warrenretina.com.
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