Pars plana vitrectomy risks mandate careful undertaking

Key Points

Most anterior segment surgeons rarely perform vitrectomy, however, so the advantages of the pars plana approach probably do not outweigh the risks, according to Dr. Duker, professor and chairman, Department of Ophthalmology, Tufts University School of Medicine, Boston.

"Anterior segment surgeons who want to be able to do PPV should take steps to flatten the learning curve," he cautioned. "Before trying it on their first patient, they need to learn and practice the technique in a wet lab and by working with a mentor. They must also be knowledgeable about diagnosing and managing complications of the pars plana approach."

"With PPV, we can remove the peripheral vitreous base, visualize any retinal surface pathology, and perform complete vitreous removal if it is indicated," Dr. Duker said.

Limbal preference

Despite the advantages of PPV, most anterior segment surgeons tend to favor limbal vitrectomy, he said, perhaps because it seems logical not to create an extra incision site when the cataract procedure already has provided two entries, but also because of a general lack of expertise.

"Most residency training programs don't teach PPV, and some anterior segment surgeons are not comfortable in diagnosing and treating the posterior segment complications that can occur with this approach," Dr. Duker said.

Posterior technique tips

For surgeons who might consider posterior assisted levitation to remove lens fragments from the vitreous, focusing attention solely on the lens fragments while ignoring the vitreous surrounding the lens fragments is dangerous, he cautioned.

"Through mechanical manipulation, you can cause undue and perhaps unseen traction on the anterior vitreous that may result in peripheral retinal pathology," Dr. Duker said. "And as you move the lens fragments anteriorly, the vitreous will follow. Consequently, vitreous to the wound, iris, and capsule are more likely unless you do a complete vitrectomy."

For surgeons who do pursue this technique, he emphasized that they should be comfortable with pars plana incisions.

"It is not a good idea to have a complicated case be your first experience with introducing a sharp instrument into the eye through the pars plana," Dr. Duker said.

He also recommended using triamcinolone to stain the vitreous, noting that a small volume (~0.1 ml) should be instilled into the anterior chamber to avoid creating a "snowstorm."

"Leaving excess triamcinolone in the eye is not particularly harmful. In fact, it may even reduce the risk of cystoid macular edema," Dr. Duker said.

He also cautioned against pulling mechanically on the vitreous and emphasized the importance of ensuring that all vitreous has been removed from the anterior chamber before the wound is closed.

"Avoid doing just a 'little vitrectomy,' " he said. "You must do enough so that the anterior chamber is clean at the end of surgery."

In addition, Dr. Duker said, surgeons should examine the peripheral retina at the end of the procedure using an indirect ophthalmoscope. Surgeons who are not comfortable using a pars plana approach may consider introducing viscoelastic through the sideport incision to elevate gently and then remove lens fragments. These maneuvers are done while carefully pushing the vitreous posteriorly, he said.