Pars plana approach can provide successful outcomes

January 1, 2009

Posterior capsule rupture with vitreous prolapse remains one of the most serious intraoperative complications during cataract surgery. Louis D. "Skip" Nichamin, MD, describes the benefits and technique for anterior vitrectomy using a pars plana approach.

Key Points

"When handled properly, the potential outcome after posterior capsule rupture can rival that of an uncomplicated case both anatomically and visually, but only if surgeons adhere to several fundamental surgical principles," Dr. Nichamin said.

"One must maintain a closed chamber, minimize turbulence and vitreoretinal traction, and achieve thorough clean-up of vitreous and remaining lens material within the anterior segment," he continued. "These principles are best achieved when anterior vitrectomy is performed using a pars plana approach." Dr. Nichamin is medical director, Laurel Eye Clinic, Brookville, PA.

"One must be prepared with the proper instrumentation but also with proper practice, which should include course study, wet lab instruction, and first-hand observation of colleagues," Dr. Nichamin said.

Benefits of the approach

One of the advantages of the pars plana vitrectomy approach is that it enables a truly closed chamber environment, which reduces intraocular turbulence, because the phaco incision is hydrated, sutured, and sealed.

As another benefit, anterior vitrectomy using a pars plana approach allows vitreous clean-up that is safer, more limited, and yet more thorough compared with anterior vitrectomy performed through the limbus.

"Because the vitreous is being pulled down, the pars plana technique allows definition of a better endpoint and can potentially decrease vitreoretinal tractional forces," he explained.

The pars plana approach also affords better access to remaining lens material, especially within the subincisional area that can be difficult to reach from the limbus.

In addition, the pars plana technique is more likely to preserve capsular support for IOL placement.

Technique

The contents of a "kit" for anterior vitrectomy through the pars plana include a disposable 20-gauge vitreous cutter, infusion cannula, 19-gauge microvitreoretinal blade, phacoglide, dispersive ophthalmic viscosurgical device (OVD), and suture material (8-0 polyglactin 910 [Vicryl, Ethicon] or 9-0 nylon), Dr. Nichamin said.

The technique is based on a bimanual approach in which a watertight limbal paracentesis is used as the site for the infusion cannula, and the vitrector is placed through the pars plana incision that is created 3.2 mm posterior to the limbus, he said.

"The incision is made using a caliper to determine the location," Dr. Nichamin said. "We like to avoid the cardinal meridia and work in the oblique meridia, typically on the side of the surgeon's dominant hand. However, the actual clock hour can be chosen for achieving the best angle to approach the remaining lens material with the cutter."

After taking down the conjunctiva and applying a small amount of cautery to the site, the pars plana incision is made by simply going in and out of the sclera with the disposable 19-gauge microvitreoretinal blade.

Offering a few tips, Dr. Nichamin said that the balance between infusion and outflow needs to be regulated to avoid chamber collapse. That balance, however, can be leveraged with an appropriate OVD.

Staining of the vitreous with triamcinolone can be very useful, he said.

Vitreous is removed using the highest possible cutting rate with the minimum required vacuum level. When removing residual lens material, however, the cutting rate should be titrated down and the vacuum increased.

"While doing these maneuvers, it is important to be able to visualize the remaining capsular support and avoid sacrificing it," he said. "When moving the cutter around, we like to release vacuum first and then commence after the cutter is repositioned."

Once the procedure is completed, the pars plana incision is cleaned and sutured. The peripheral retina should be examined either in the operating room or at an early follow-up visit.

New technology

Dr. Nichamin acknowledged that smaller-gauge (23- or 25-gauge) sutureless technology now is available for vitrectomy. He said that he believes, however, that it suffers from various limitations, including a lack of tensile strength and difficulty entering the soft eye using the typical trocar system.

Dr. Nichamin said tremendous advances have been made in modern phaco that have made cataract surgery a remarkably reproducible procedure with unprecedented refractive outcomes. Although surgeons generally think of innovations in equipment and surgical techniques as the primary contributors to progress, he said that the ability to minimize complications and control them when they occur may be the most incredible achievement.

"However, it is important to discuss complications candidly with patients," Dr. Nichamin concluded. "They still cannot be avoided completely, and what is important, then, is how they are managed when they occur."

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