Better instrument design, increased indications boost popularity of MIVS

Microincision vitrectomy surgery has reached today what phacoemulsification achieved in the mid-1990s — self-sealing wounds, a wide array of instrumentation, better fluidics and, most importantly, wide acceptance by the current generation of surgeons.

Fujii and colleagues first reported on microincision vitrectomy surgery (MIVS) in 2002. By 2005, most U.S. surgeons had access to such systems, and the American Society of Retina Specialists 2006 Preferences and Trends Survey reflected that, with almost 90% of retinal specialists reporting at least one use of MIVS and almost half reporting frequent use. In 2008, the same survey showed that 71% of surgeons used MIVS in at least 80% of cases when managing an epiretinal membrane without any other coexisting retinal abnormalities.

Seenu M. Hariprasad, MD, associate professor of ophthalmology and chief of the vitreoretinal service at the University of Chicago Department of Surgery, said MIVS offers clear advantages, more patient comfort, less surgically induced inflammation and reduced risk of postoperative corneal astigmatism, which all lead to quicker visual recovery.

Although overall surgical times are not shorter than with 20-gauge vitrectomy, he said he spends less time creating and later suturing scleral incisions, as well as less time swapping instruments through the entry ports. This offsets the increased time required by slower vitreous shaving rates with MIVS.

Andrew Moshfeghi, MD, creates self-sealing wounds in nearly all cases when using a 25-gauge system and an angled incision. Image: Moshfeghi A

“If you look at my practice, 95% of cases are done with microincisional vitrectomy, and the rest are hybrid cases involving one enlarged scleral wound to accommodate a 20-gauge instrument and the other two remaining MIVS,” Dr. Hariprasad said. “I haven’t done a 100% 20-gauge surgery in at least 2 or 3 years.”

Evolving surgical techniques

The primary advantage is patient comfort, Dr. Hariprasad said. Procedures done by 20-gauge vitrectomy require suturing, while MIVS does not require taking down the conjunctiva, and the scleral wound is self-sealing, Dr. Hariprasad said.

“If you’ve ever had an eyelash in your eye, you know how it feels. Imagine having three Vicryl suture knots,” he added.

A second benefit is that the eye is quieter after MIVS because the procedure is less invasive and disruptive to the ocular surface, subconjunctival space and Tenon’s space, Dr. Hariprasad said.

Finally, visual recovery is faster because the lack of sutures induces less corneal astigmatism.

Andrew A. Moshfeghi, MD, MBA, an assistant professor of ophthalmology at University of Miami Miller School of Medicine, was completing his fellowship when MIVS systems were first introduced. He readily adopted a 25-gauge system. However, the extreme flexibility of the instruments, somewhat slower vitrectomy cutting and difficulty injecting and removing silicone oil led him to migrate his more challenging cases to a 23-gauge system and reserve 25-gauge vitrectomy for posterior cases such as macular puckering and macular holes.

Using 23-gauge systems allowed him to tackle vitreous hemorrhages, diabetic traction retinal detachments and with non-clinical vitreous hemorrhages or retinal detachments in patients with diabetes.

“However, I didn’t like the fact that the wounds weren’t convincingly and consistently sealed at the end of a 23-gauge case using a beveled incision,” Dr. Moshfeghi said. “I either felt uncomfortable with the way the wounds looked at the conclusion of the case, or I ended up throwing a suture, or both. So all too often I found myself closing nearly all of the wounds.”

He continued this way until the introduction of a 25-gauge system with a stiffer handpiece, the 25+ that works with the Constellation and Accurus systems (both Alcon). It allows him to create a self-sealing wound nearly 100% of the time using an angled incision. He uses this in 90% of his Constellation cases, including expanded indications such as drainage of choroidal hemorrhage, vitreous hemorrhage and scatter endolaser for a diabetic patient without a tractional detachment but with proliferative diabetic retinopathy. Dr. Moshfeghi said he switches back to 23-gauge surgery only for cases involving anterior work at the vitreous base, pars plana or lenticular work, or a giant retinal tear.

Earlier this year, Alcon announced a voluntary recall of the Constellation system because of various hardware and software problems, according to the FDA website. The voluntary recall does not require the device to be removed from any health care facility. The notice said that Alcon representatives will visit all U.S. facilities to update software, replace touch screens and circuit boards following FDA clearance of its upgrades. Alcon continues to market the Constellation while awaiting FDA clearance of its upgrades and has successfully completed nearly 100 percent of upgrades outside the United States.

Since the Constellation recall, Dr. Moshfeghi said he has returned to using the 23-gauge trocar-cannula systems while using the Accurus, and he intends to return to the 25+ platform when the Constellation recall is resolved.

“Right now the question is not whether microincisional vitrectomy is good or not,” Dr. Hariprasad said. “It’s very clear that the community believes that it’s a very good thing. The question is, in what indications can we push the system to the max?”

Seenu M. Hariprasad

The stiffer instrumentation and advanced fluidics let surgeons repair advanced retinal disorders such as retinal detachments farther out in the periphery, which was not always the case before 23-gauge systems and the 25+ handpiece for the Constellation system, Dr. Hariprasad said.

“Anything that deals with the macula, which is where epiretinal membranes occur, is easy with MIVS,” Dr. Hariprasad said. “But retinal detachment repair requires working in the periphery of the retina, which requires the instruments to not bend because you want to reach with the instruments.”

While the 2008 ASRS Preferences and Trends Survey showed that most of the respondents were using MIVS just to manage epiretinal membrane, “My suspicion is that with stiffer instrumentation, the masses are going to look at MIVS to repair more advanced vitreoretinal disorders,” Dr. Hariprasad said, including tractional retinal detachments and proliferative vitreoretinopathy.

According to Pravin U. Dugel, MD, at Retinal Consultants of Arizona, “People say, ‘I use MIVS for easy cases and I reserve my 20-gauge for the harder cases.’ And for me it’s exactly the opposite. You want the fluidic advantage of a smaller gauge for the harder cases. … I use the 25+ system with the Constellation Vision System in 100% of my surgeries. However, if I was forced to use the 20-gauge system, I’d rather use it for the simpler cases, such as a vitreous hemorrhage or an epiretinal membrane, where the fluidics may not matter as much. For the more complicated cases, such as traction retinal detachments or retinal detachments with proliferative vitreoretinopathy, the fluidic advantage of a smaller gauge, such as the 25+, is very important for me.”

Advanced instrumentation

At first, a lack of 25-gauge instruments severely limited the types of procedures that could be performed. Light sources and silicone injection/extraction devices were two major deficiencies in particular, Dr. Hariprasad said. But now, a xenon light source provides illumination, and a cannula for silicone oil injection and curved endolaser probes for peripheral photocoagulation are available.

“In 2005 all we had in MIVS was a forceps and maybe some few basic instruments. Now pretty much 95% of the armamentarium that I have in 20 gauge, I have also in 23 gauge,” Dr. Hariprasad said. “The only thing that I’m missing is a pars plana lensectomy fragmatome to take out a lens and subretinal instrumentation. Despite this, I am still able to do the majority of pars plana lensectomies with the 23-gauge vitreous cutting device.”

Dr. Dugel said he is using his cutter to simulate other instruments, reducing by 80% the need for forceps and scissors. He does not need as many surgical personnel, and the turnover time between cases is faster. Dr. Dugel is preparing a paper outlining the specific impact of new surgical techniques on the management of his practice’s surgical center, Spectra Eye Institute.

Pravin U. Dugel

Dr. Dugel explained how he simulates multiple instruments with his 25+ system. The small size of the 25+ instruments and the fact that the port is located close to the tip is an advantage, he said. This often replaces the need for horizontal scissors or forceps. In addition, the tip can reach places where surgeons might not have reached before.

New parameters also allow Dr. Dugel to create new techniques. A parameter called “duty cycle control” adjusts the percentage of time the cutter remains open in a given cut cycle. Flow rates do not slow, even when cutting at the highest rate. This lets Dr. Dugel simulate horizontal or vertical scissors with his vitreous cutter, or even simulate a phacofragmatome.

Dr. Dugel’s Constellation Vision System also has proportional reflux, a controlled method of hydrodissection emanating from the cutter. Originally designed to push out the accidental incarceration of retina from the cutter, he uses it to separate abnormal fibrous tissue from normal retinal tissue in a surgeon-controlled manner. Dr. Dugel has named this new surgical technique “proportional reflux hydrodissection.”

“With all tractional retinal detachments, I use proportional reflux hydrodissection,” Dr. Dugel said. “Give it a try. It doesn’t cost anything. It takes no time or effort because I’m already inside the eye. All I have to do is move my foot and click the pedal.”

The technique successfully separates retina from fibrous tissue in at least 70% of Dr. Dugel’s cases. He reverts to other instruments, such as horizontal scissors, when it does not.

“Not only can you use a surgical technique that I think is a lot safer, but you can also decrease your number of instrument exchanges,” Dr. Dugel said. “There’s safety in not having to constantly come out of the eye and change instruments.”

Another advantage is a foot pedal that also allows the surgeon to control both the infusion line and the wattage of the laser, Dr. Moshfeghi added.

Instead of relying on a scrub tech to clamp the infusion line on and off, which can delay procedures at crucial points in the case or even cause bubbles in the eye, he uses the foot pedal to control infusion at the pump. The foot pedal also controls the laser power as he moves from the posterior retina to the peripheral retina. Instead of telling the technician to power down from 300 mW to 200 mW to 180 mW, he can control it himself. The laser can also be turned on and turned off to standby mode with the foot pedal.

“Having all of that, I feel like I don’t even need my scrub tech,” Dr. Moshfeghi said.

Complications considered

Dr. Moshfeghi addressed a theoretical concern that phakic patients may experience higher cataract rates caused by the tip of the cannula on all three sides coming very close to the equator of the lens. But, he added, studies are needed to see if this is borne out.

He said he continues to use sutures after 23-gauge surgical procedures, admitting that he is “a major outlier” to do so. But, he added, “I never ever felt uncomfortable leaving the operating room thinking, ‘Maybe I should have thrown a stitch in that scleral wound,’ or ‘I wonder how that patient is going to look tomorrow morning.’”

After the completion of 25-gauge MIVS cases, although the wounds look sealed, they probably are still not perfectly watertight or airtight, Dr. Moshfeghi said. Bacteria or subconjunctival quinolones can get into the eye and create retinal, macular or optic nerve toxicity. He places subconjunctival antibiotics well away from the sclerotomy sites, especially when using gentamicin for patients with penicillin allergies.

The association between 25-gauge vitrectomy and an elevated incidence of endophthalmitis is controversial. The rarity of endophthalmitis and the difficulty of comparing two surgeons’ techniques make it difficult to create the large number of cases needed to prove any statistically significant conclusions, Dr. Hariprasad said.

An early study showed a 12-fold increase in the risk of endophthalmitis in 23-gauge vitrectomy vs. 20-gauge vitrectomy. “This caused us some pause in our enthusiasm,” Dr. Hariprasad said. While there were some confounding problems in the study — wound construction was not ideal and angles of entry differed, for example — it affected many surgeons.

“Suddenly what was felt to be a fantastic thing was not as fantastic as we thought,” Dr. Hariprasad said.

However, although two large retrospective studies of 4,400 patients or more report an increased risk, three similar studies of 3,500 patients or more report no difference in endophthalmitis rates between 20-gauge and MIVS cases. Only one large study of more than 4,000 patients with 23-gauge vitrectomy has been published, and it found no increase in endophthalmitis.

“The advantages of microincisional outcomes so incredibly outweigh the small theoretical risks that I do 95% of my cases with microincisional vitrectomy compared to older generation 20-gauge vitrectomy,” Dr. Hariprasad said.

“The bottom line is that microincisional vitrectomy is the future,” Dr. Dugel said. “Its advantage is not only outside the eye, in being sutureless surgery, but its most important advantage is inside the eye in allowing for better fluidic control and therefore safer surgery.” – by Ryan DuBosar

Editor’s note: Since the writing of this article, Bausch + Lomb has introduced the Stellaris PC Vision Enhancement System, a combined vitrectomy and phacoemulsification system. We look forward to reporting on surgeons’ experiences with this new system in upcoming issues of Ocular Surgery News.

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References:

• Fujii GY, De Juan E Jr, Humayun MS, et al. Initial experience using the transconjunctival sutureless vitrectomy system for vitreoretinal surgery. Ophthalmology. 2002;109(10):1814-1820.
• Hu AYH, Bourges J-L, Shah SP, et al. Endophthalmitis after pars plana vitrectomy: a 20- and 25-gauge comparison. Presented at: American Society of Retina Specialists annual meeting, Maui, Hawaii; Oct. 14, 2008.
• Kunimoto DY, Kaiser RS. Incidence of endophthalmitis after 20- and 25-gauge vitrectomy. Ophthalmology. 2007;114(12):2133-2137.
• Mason JO 3rd, Yunker JJ, Vail RS, et al. Incidence of endophthalmitis following 20-gauge and 25-gauge vitrectomy. Retina. 2008;28(9):1352-1354.
• Mittra RA, Pollack JS. ASRS Preferences and Trends Survey 2008.
• Scott IU, Flynn HW Jr, Dev S, et al. Endophthalmitis after 25-gauge and 20-gauge pars plana vitrectomy: incidence and outcomes. Retina. 2008;28(1):138-142.
• Shimada H, Nakashizuka H, Hattori T, Mori R, Mizutani Y, Yuzawa M. Incidence of endophthalmitis after 20- and 25-gauge vitrectomy causes and prevention. Ophthalmology. 2008;115(12):2215-2220.

• Pravin U. Dugel, MD, can be reached at Retinal Consultants of Arizona, 1101 E. Missouri Ave., Phoenix, AZ 85014; 602-222-2221; fax: 602-266-2044; e-mail: pdugel@gmail.com. Dr. Dugel is a consultant to Alcon Surgical, Alcon Pharmaceutical, AMO, ArcticDx, Genentech, Regeneron, NeoVista, MacuSight, Bausch + Lomb Pharmaceutical, QLT, Novartis and Ora.
• Seenu M. Hariprasad, MD, can be reached at Department of Ophthalmology and Visual Science, University of Chicago, 5841 S. Maryland Ave., MC 2114, Chicago, IL 60637; 773-795-1326; e-mail: retina@uchicago.edu. Dr. Hariprasad is a consultant to Alcon, Allergan, Genentech, Optos, OD-OS and Pfizer. He is on the speaker’s bureau for Alcon, Allergan, Genentech and Pfizer.
• Andrew A. Moshfeghi, MD, MBA, can be reached at University of Miami Miller School of Medicine, 7101 Fairway Drive, Palm Beach Gardens, FL 33418; 561-355-8608; fax: 561-355-8601; e-mail: amoshfeghi@med.miami.edu. Dr. Moshfeghi has served as a compensated consultant to Alcon.