The evolution of pars plana vitrectomy from its advent in the mid-1970s has brought significant advances in instrument design and surgical techniques, leading to better outcomes, more-streamlined and cost-effective procedures and better patient satisfaction. Mirroring the experience of anterior segment surgeons, vitreous surgery during that time has become progressively less-invasive, allowing more rapid visual recovery thanks to smaller incisions made possible with smaller probes and evolving surgical techniques.

The last two years have seen the introduction and growing popularity of transconjunctival sutureless vitrectomy using 25-ga. probes rather than the standard 20-ga. technology. Those who have made the transition cite significant advantages in terms of greater surgical control and precision, improved patient outcomes, and greater patient acceptance.

Instruments for 25-ga. Vitreous Surgery
Vitreoretinal surgeons now also have an excellent array of instruments for use in 25-ga. vitrectomy, and every month seems to bring something new. Many new forceps are now available, some of which are disposable. Both Alcon and Dutch Ophthalmic, for example, make a series of 25-ga. disposable forceps that work very well. Because the 25-ga. instruments are so delicate, they’re a little harder to care for. I tend to use of lot of disposable forceps, which cost about $50. Their cost is justified when considering that you may spend up to $2,000 for non-disposable forceps that may last just a couple months. Xenon light sources are improving the illumination of small-incision vitreous surgery. In addition to the chandelier systems, another exciting new advance is a combined fiber optic light/laser probe made by Synergetics, (syngereticsusa.com) an instrument maker in St. Charles, Mo. They wrap the light coaxial around the laser fiber, and have designed it to accommodate 25-ga. surgery. The probe extends and curves, so not only are you able to view objects with the powerful xenon light, but you can also use the laser and light simultaneously while using your free hand for scleral depression externally. Highly complicated procedures for which you need angled instruments may require that you open the eye with 20-ga. instruments. Some procedures may call for the use of both 20- and 25-ga. instruments. It’s entirely feasible, for example, to open one sclerotomy with a 20-ga. instrument while use 25-ga. tools for other steps in the procedure.
Synergetics’ 25-ga. Endo Illuminator (left) and Wide Field Monofiber for Scissors/Forceps.

Why Make the Transition?

Site-alignment cannulas are made of rigid polyamide tubing.

In 1992, I described a sutureless, 25-ga. vitreous biopsy instrument in collaboration with Storz, which was later independently developed by Robert Josephberg, MD and commercialized by Visitec. The technology and technique for 25-ga. total vitrectomy followed some 10 years ago at the Microsurgical Advanced Design Laboratory (MADLAB), now part of the Doheny Retina Institute, under the direction of Eugene de Juan, MD. Dr. de Juan and his colleagues later collaborated with Bausch & Lomb to develop 25-ga. technology in what is now called the 25-TSV (transconjunctival standard vitrectomy) system, used in conjunction with the company’s Millennium vitrectomy machine. Also offering 25-ga. vitrectomy technology is Alcon, which has collaborated with the Dutch Ophthalmic Research Center (DORC) to design 25-ga. technology for use with its popular Accurus vitrectomy system. Both companies’ systems are built on a platform of standard vitrectomy machine instrumentation, with the exception that the probe and ancillary instrumentation are smaller.

Light pipe, vertical scissors, micro-pic forceps, rigid intraocular picks, tissue manipulator-pic, aspirator and an extendable curved pick.

For those considering making the switch from 20-ga. to 25-ga. vitrectomy, the latter offers a number of advantages worth considering. 

 • Patient satisfaction. As surgeons, we’re essentially selling patient satisfaction. Improved vision is just one component of that effort. We must also strive to make the patient as comfortable with his or her surgical experience as possible. In my experience, there is no question that patients are more comfortable after 25-ga. retinal surgery. They experience essentially no external irritation postoperatively. The eye looks normal much more quickly than with 20-ga. surgery. It is not uncommon on the first-day postop after the staff removes the patient’s patch that I find it difficult to tell which eye underwent the surgery.

With the 25-ga. system there is less residual astigmatism and quicker visual recovery thanks to the reduced diameter—0.5 mm vs. 1.0 mm with 20-ga. surgery—of the incision. Carl Awh, MD has recently shown that the removal of a macular pucker using a 20-ga. vitrectomy might require one to two months for full visual recovery, while this happens within a week or so with the 25-ga. technique. Although the final visual outcome may be the same with both techniques, patients appreciate the quicker functional recovery. I have had patients who received 20-ga. surgery in one eye and later developed the same problem in the fellow eye, for which they underwent the 25-ga. procedure; their testimonials in favor of the latter attest to why 25-ga. vitrectomy is here to stay. 

 • Operative time. Although vitreous surgery back in the 1970s and 1980s extended to three to six hours, standard 20-ga. surgeries today take about 45 to 90 minutes for most cases. The 25-ga. surgeries that I have done not uncommonly take me about 15 minutes. Patients are amazed, as I apply the patch, that the procedure is done that quickly. The foreshortened operative time is partially because you require no sutures to close the surgical wound. Taking that time off the clock offsets the greater cost of the disposable surgical pack, which exceeds that of the 20-ga. procedure by some $50 to $75. 

 • An expanded range of surgical indications. We have seen a relaxation of the kinds of conditions on which surgeons are willing to operate. Macular pucker is one example. Macular pucker can reduce vision minimally or severely. Years ago with 20-ga. technology we would never consider bringing a macular pucker to the operating room unless the vision was down to 20/80 or 20/100.

Today it is not uncommon to operate on a macular pucker with 20/25 vision if the patient is complaining of the resultant visual distortion. Surgeons routinely are beginning to use 25-ga. surgery to treat vitreomacular traction and vitreous opacities, particularly if the patient is pseudophakic. I’ve always considered myself conservative about offering patients surgery to remove significant vitreous floaters, but this is beginning to relax. I now feel more comfortable offering 25-ga. vitrectomy in cases of a non-clearing vitreous hemorrhage.

 • Ease of transition from 20- to 25-ga. surgery. You don’t need to purchase an entirely new machine to make the transition. With both the B&L Millennium and Alcon Accurus systems, the mechanics required to drive the 25-ga. probe are already in the machine. You just need to buy the appropriate packs and hand instruments to accommodate the new technique.

The biggest difference between the two systems is the size of the probe and the technology of what drives it. B&L’s system features an electric handle, which is about 16 times heavier than Alcon’s pneumatically driven probe. Both cut well and produce favorable results. I happen to prefer pneumatically driven probes, so I am more comfortable with the Accurus platform.

Note also that 25-ga. vitreous surgery does not entirely supplant the 20-ga. procedure in the surgeon’s armamentarium. The latter is still the preferred technique for a number of indications including complex retinal detachments, dislocated nuclear material, or in any case where true bimanual surgery or the use of angled instruments is preferred. While silicone oil cannot be injected through a 25-ga. lumen, the oil may still be injected at the end by simply enlarging the initial 25-ga. sclerotomy. The recent introduction of high quality xenon light sources coupled with 25-ga. chandelier systems will expand 25-ga. surgery even more by allowing the use of bimanual 25-ga. instruments.

Technical Pearls
There is a learning curve in the use of 25-ga. vitreous surgery. Even though the instruments are smaller, the surgery technically is not easier than that of the 20-ga. technology. If anything, it is more challenging, especially for the beginning vitreoretinal surgeon. For those considering adding 25-ga. vitrectomy to their repertoire or are just starting out, I can offer some surgical pearls learned during my two years performing the newer technique. 

Bausch & Lomb’s Millennium system.

 • Start with cases best suited to allow you to get comfortable with the thinner and more flexible instruments of the 25-ga. system. This means your accuracy must be right on. It also makes it harder to move the eye because the instruments bend as you torque the eye. Surgeons are accustomed to using instruments to manipulate the eye’s position during vitreous surgery. With the 25-ga. technique, surgeons will be more successful using wide-angle visualization to view the periphery and pivot the instruments around the sclerotomy site rather than rotating the eye.

Begin with a virgin eye, one that has not previously undergone surgery. Macular pucker is a good choice if you are just starting out. Of course, macular puckers vary in their pathoanatomy. Some appear thin and glassy on the retinal surface, and these are difficult to lift using the flimsy and flexible 25-ga. instrument. Until you get more experience, you are better off operating on patients with a thick and robust epiretinal membrane causing a macular pucker. These cases are more amenable to grabbing and peeling using the 25-ga. instrument.

 • An important part of the 25-ga. technique is to displace the conjunctiva laterally at entry so that when you remove the alignment system at the end, the conjunctiva will slide over so that its hole misaligns with that of the sclera providing protection to the scleral entry.

The alignment system, designed by Dr. de Juan and coworkers, is a thin-walled polyamide plastic tube with a grommet on the outside. As the conjunctiva is displaced laterally, the alignment tubing held coaxially around a metal trocar is slowly advanced through the eyewall. The trocar is withdrawn, and the tubing then provides the entry portal into the vitreous throughout the case.

 • Be patient when introducing the alignment system. Use steady, even pressure with minimal oscillation, and don’t be in a hurry. With patience, the cannula will finally pop into the vitreous cavity. Surgeons who try to hurry this step will get frustrated and find it difficult to insert the cannula into the eye. 

 • When you withdraw the trocar, the alignment system stays in place. This maintains an open pathway between the outside of the eye and the vitreous cavity. Because the grommet is visible externally, you aim for it when introducing and withdrawing the 25-ga. instrument.

 • At the end of the operation, simply grasp the grommet and gently pull away, removing the cannula from the eye.

The conjunctiva relaxes back to its usual position and the scleral opening contracts beneath the conjunctiva. Because you are not using stitches, the scleral opening does not fully close. This is usually not a concern, however, because vitreous gel will oppose the inside scleral opening to plug the puncture site from within preventing leakage. 

 • Memphis surgeon Steven Charles, MD—initially a critic and now an advocate of 25-ga. surgery— lessens the chance of a leaky wound by placing a one-third-fill air bubble to seal the sclerotomy just as air or gas seals retinal breaks. Since I have started using air in the eye, I have found that I almost never need suture the wound. This maneuver has cut down on my leaks, and has also reduced my incidence of hypotony. The air bubble is a great trick to keep you out of trouble when you make the transition from 20- to 25-ga. surgery.

Alcon’s Accurus 25-ga. handpiece.

There is a concern that if the vitreous doesn’t plug well, the eye will be too soft and hypotonous on the first day postop. In reality, significant hypotony complications are rare among surgeons now performing 25-ga. surgery. Naturally, eyes undergoing 25-ga. surgery will be often slightly softer on the first day postop than those closed with a suture.

One criticism of using air is that it increases the risk of cataract. In fact, cataract is a routine sequela of all vitrectomies no matter what technique you use. Although the cause of cataract after vitreous surgery is speculative, Nancy Holcamp, MD, has proposed that the cataractogenesis may be related to the increased oxygen levels in the eye after vitrectomy. The oxygen level—which increases in both 20- and 25-ga. surgery—may be the driving force of progressive nuclear sclerosis. Adding a small air bubble into the eye probably does slightly increase your concern about cataract, but cataract will develop regardless of your technique. In any event, the risk of cataract with 25-ga. vitreous surgery seems to match that of the 20-ga. technique. 

 • Guard against endophthalmitis. There is no data to suggest that 25-ga. technology increases the risk of endophthalmitis compared with that of 20-ga. surgery. That risk is probably less than 0.1 percent of cases. The theoretical concern about endophthalmitis is mostly due to the fact that you’re going through the conjunctiva, which is populated with bacterial flora, and that you may leave a "vitreous wick" in the scleral opening.

Most surgeons therefore apply an iodine preparation to the conjunctiva prior to surgery. This step is vital to reduce the conjunctiva’s bacterial flora. Another prudent step is to start the patient on a late generation fluoroquinolone antibiotic q.i.d. one day before surgery.

Subconjunctival antibiotics can further cut the incidence of endophthalmitis. Anterior segment surgeons have moved away from using subconjunctival antibiotics, and many retinal surgeons have done the same. But many other retinal surgeons still use them, and whether this is indicated for 25-ga. vitrectomy is a matter of personal choice. If you do use subconjunctival antibiotics, be careful to apply the medication to the inferonasal part of the conjunctiva, the one quadrant untouched in most conventional vitreoretinal surgeries. Be careful never to use aminoglycosides in 25-ga. cases as these can be extremely toxic if the medication enters the eye accidentally.

 • Postoperatively, 25-ga. vitreous surgery has to some degree relaxed my usual conservative nature regarding patient instructions. Previously, surgeons would restrict reading and driving for a while, and make sure the eye does not get wet. Usually with 25-ga. surgery, I will see the patient one day postop and give him or her minimal, if any, restrictions. Because the eye heals so quickly, patients can resume their normal tasks, and need not worry about the eye getting wet. I will also take the patient off cycloplegics sooner than with 20-ga. vitreous surgery. The air bubble is a little annoying, and takes a couple days to go away. During that time, the patient is restricted from flying.

A Parallel Evolution
Surgeons sometimes liken the evolution of vitreous surgery to that of cataract procedures. In both cases there has been a move toward smaller wounds that create less surgical trauma and swifter visual recovery while streamlining the procedure. Both cases initially met with resistance from surgeons comfortable with their customary technique and happy with its results. But just as sutureless small-incision phacoemulsification has become routine in the last decade, so too in the coming years might we see 25-ga. transconjunctival vitreous surgery become standard practice. 

Dr. Packo is an associate professor of ophthalmology at Rush Medical College and director of the Retina Section at Rush-Presbyterian-St. Luke’s Medical Center, both in Chicago.