Clarifying Common Misconceptions About Small-gauge Vitreoretinal Surgery

With few exceptions, MIVS is suitable for almost all cases.

BY FRANCESCO BOSCIA, MD

According to the results of the American Society of Retina Specialists' 2008 Preferences and Trends Survey, 65% of U.S. retinal specialists report using a 23-gauge vitrectomy system. This is an increase of 43% over the previous year. However, 66% expect that in the next 5 years, they will be performing primarily either 23-g or 25-g procedures with limited 20 g.

In my practice, I use a 25-g approach for macular surgery and a 23-g system for all other cases, except those in which the eye already has undergone multiple procedures. The situations in which I use a 23-g or 25-g approach include complex cases, such as proliferative vitreoretinopathy, complicated retinal detachment and trauma.

Here, I will list common misconceptions about small-gauge retinal surgery and explain why they are false, based on my experience and that of other surgeons. I'll discuss why I believe they do not apply today.

Common Misconceptions

■ The vitreous cannot be removed completely. With the appropriate maneuvers, all of the vitreous can be removed with a small-gauge system. After I remove the bulk of the vitreous under wide-angle visualization, I complete the removal by depressing the sclera and working under direct coaxial microscope visualization.

It is also important to note, as shown in some studies,^1,2 that in certain cases it is not necessary to completely remove the vitreous. The authors reported that nonvitrectomizing epiretinal membrane removal appears to decrease the postoperative development or progression of nuclear sclerosis.

■ Small-gauge surgery increases the risk for retinal breaks and detachments. In contrast to this statement, Scartozzi and colleagues³ discovered a trend in slightly lower rates of intraoperative sclerotomy-related retinal breaks with 25-g vitrectomy compared with 20 g, although the difference was not statistically significant. In addition, several published case series^4–8 indicate the rates of retinal breaks and detachments are not necessarily higher in 25-g procedures than in 20-g surgeries.

■ Unsutured sclerotomies leak. Leakage from unsutured wounds can cause complications, but the surgeon can take steps to prevent it with proper wound construction. The sclera should be incised parallel to the scleral fibers to render the sclerotomy openings more linear compared with a perpendicular entrance. Physicians can increase the length of the scleral tunnel by a factor of 3 just by decreasing the angle of incidence from 30° to 10°.

When performing surgery on myopic eyes, physicians should be more cautious about using a small-gauge system and consider suturing when necessary. Because myopes have thinner sclera, the incisions are shorter than in emmetropic eyes even when they are similarly angled.

I also perform a partial fluid-air exchange at the end of each surgery. The superficial tension it creates helps to prevent the intraocular content from extruding. In addition, surgeons can use a releasable suture technique, as described by Lee,⁹ when necessary. This type of technique allows tight closure of the sclerotomies in the early postoperative period when the risk of hypotony is highest. Physicians then can remove the sutures, avoiding suture-related complications, such as inflamed conjunctiva and scleromalacia (Figures 1 and 2). I do not consider the placement of an 8 or 9/0 Vicryl suture, or a releasable suture, a failure of the sutureless approach. The eye still will be less inflamed than it would be following a 20-g procedure.

Figures 1 and 2. Suturing required for 20-g retinal surgery can lead to complications such as inflamed conjunctiva and scleromalacia.

■ The risk of endophthalmitis increases. While some studies have suggested the rate of endophthalmitis is higher with small-gauge surgeries, others have not. As with any intraocular surgery, steps must be taken to decrease the risk.

Wound construction as described above is one step. In addition, in my practice, I prep the conjunctival sac with betadine for at least 3 minutes before beginning the surgery. I devote maximum care to displacing the conjunctiva and creating a long scleral tunnel. At the conclusion of surgery, I carry out a partial fluid-air exchange to help seal the wound and reduce the space favorable to microbial infiltration.

■ Instruments are too flexible. Recently, many improvements were made to the instrumentation associated with small-gauge procedures. Increased rigidity and easier globe penetration are among them. In addition, better light sources and chandelier designs have facilitated bimanual techniques.

Two instruments I have found useful are curved horizontal scissors for delamination and a 25/23/20-g sclerotomy adaptor for cases in which I want to enlarge one entry site. Also, vented gas forced infusion technology has provided better control of eye pressure during surgery.

■ Vitrectomies take too long. In my experience, even though the time it takes to perform a vitrectomy is longer for small-gauge surgery, the shorter, initial and concluding steps balance that time.

■ Silicone oil cannot be used. In general, you should avoid silicone oil tamponade in retinal surgery unless you can remove it once the retina stabilizes. Research^10,11 has shown there are safe and effective techniques for silicone oil removal for both 23-g and 25-g procedures.

Today's Systems Safe and Effective

I have found the transition to small-gauge retinal surgery advantageous. As long as surgeons are cautious when performing surgery on myopic eyes, on eyes that have had multiple previous surgeries and take steps to prevent wound leakage and endophthalmitis, the current systems are very safe and effective. As a result, my patients experience reduced postoperative inflammation, faster recovery with less discomfort, diminished conjunctival scarring and less postoperative astigmatism.

Francesco Boscia, MD, is a professor in the department of ophthalmology and otolaryngology at the University of Bari in Bari, Italy.

References

1. Sawa M, Ohji M, Kusaka S, et al. Nonvitrectomizing vitreous surgery for epiretinal membrane long-term follow-up. Ophthalmology. 2005;112:1402–1408.
2. Saito Y, Lewis JM, Park I, et al. Nonvitrectomizing vitreous surgery: a strategy to prevent postoperative nuclear sclerosis. Ophthalmology. 1999;106:1541–1545
3. Scartozzi R, Bessa AS, Gupta OP, Regillo CD. Intraoperative sclerotomyrelated retinal breaks for macular surgery, 20- vs 25-gauge vitrectomy systems. Am J Ophthalmol. 2007;143:155–156.
4. Okuda T, Nishimura A, Kobayashi A, Sugiyama K. Postoperative retinal break after 25-gauge transconjunctival sutureless vitrectomy: report of four cases. Graefes Arch Clin Exp Ophthalmol. 2007;245:155–157.
5. Lakhanpal RR, Humayun MS, de Juan E, et al. Outcomes of 140 consecutive cases of 25-gauge transconjunctival surgery for posterior segment disease. Ophthalmology. 2005;112:817–824.
6. Fujii GY, De Juan E, Humayun MS, et al. Initial experience using the transconjunctival sutureless vitrectomy system for vitreoretinal surgery. Ophthalmology. 2002;109:1814–1820.
7. Ibarra MS, Hermel M, Prenner JL, Hassan TS. Longer-term outcomes of transconjunctival sutureless 25-gauge vitrectomy. Am J Ophthalmol. 2005;139:831–836.
8. Shaikh S, Ho S, Richmond PP, Olson JC, Barnes CD. Untoward outcomes in 25-gauge versus 20-gauge vitreoretinal surgery. Retina. 2007;27:1048–1053.
9. Lee BR, Song Y. Releasable suture technique for the prevention of incompetent wound closure in transconjunctival vitrectomy. Retina. 2008;28:1163–1165.
10. Oliveira LB, Reis PA. Silicone oil tamponade in 23-gauge transconjunctival sutureless vitrectomy. Retina. 2007;27:1054–1058.
11. Kapran Z, Acar N. Removal of silicone oil with 25-gauge transconjunctival sutureless vitrectomy system. Retina. 2007;27:1059–1064.