Peer Review | Jul 2005
Pars Plana Anterior Vitrectomy
Patty Lin, MD, MBA
During cataract surgery, it is imperative to quickly recognize complications such as a posterior capsular tear with associated vitreous loss. One must attempt to maintain a controlled working environment while avoiding subsequent problems, including hypotony and vitreoretinal traction. The main goals of anterior vitrectomy are to free the anterior segment of vitreous and to release any vitreous traction, which may cause breaks or tears in the retina. Important matters to consider when performing anterior vitrectomy include the accessibility of vitreous and retained lenticular tissue, minimization of secondary complications, and optimization of visual and surgical outcomes.
TRADITIONAL ANTERIOR VITRECTOMY
When the posterior capsule is compromised and the anterior vitreous face is disrupted, anterior vitrectomy using a single-piece vitrectomy cutter through the original phaco incision is commonly employed. Tan and Karwatowski2 investigated the final visual outcome of patients who underwent unplanned anterior vitrectomy during phacoemulsification cataract surgery in a university teaching hospital. They reported vitreous loss requiring anterior vitrectomy in 3.6% of eyes (92 out of 2,538). Of 57 eyes that underwent anterior vitrectomy that did not have preexisting eye disease, 86% achieved a final visual acuity of 20/40 or better. Furthermore, 77.2% achieved a visual acuity of 20/30. The most common complication of a poor visual outcome, defined as visual acuity worse than 20/40, after anterior vitrectomy was cystoid macular edema in five eyes (8.8%). They noted that the visual outcomes after anterior vitrectomy for complicated cataract surgery compared well with those of other studies.
PARS PLANA ANTERIOR VITRECTOMY
Vitreous prolapse is manageable using a transconjunctival, 25-gauge pars plana vitrectomy with a sutureless, self-sealing incision.3-5 Insertion of an anterior chamber infusion cannula passes through a limbal sideport, and the corneal wound is cleared of any vitreous with an iris spatula through the paracentesis site. Irrigation from the infusion port maintains IOP and pushes the vitreous posteriorly. Next, one inserts a 25-gauge trocar and cannula 3mm posterior to the limbus through the pars plana and introduces a 25-gauge cutter for vitreous removal. Following the completion of the vitrectomy, one removes the 25-gauge cannula and applies pressure for wound closure without sutures.
Pars plana anterior vitrectomy has several advantages compared with current methods for dealing with vitreous loss. Anterior vitrectomy employs continuous infusion and aspiration through the same instrument and incision, a circumstance that can cause further vitreous prolapse toward the incision.4 The cutter is usually used at a slow rate with a large aspiration port, which can hydrate the vitreous and exert greater traction on the peripheral vitreous and retina.4 Complete vitreous removal from the corneal wound and anterior chamber may be difficult due to fluid flowing out of the wound and limited accessibility.
With a pars plana anterior vitrectomy, the pars plana incision can be placed in a position that offers optimal access to the remaining lenticular material. By allowing the surgeon to pull down prolapsed vitreous from the anterior chamber, the posterior approach can reduce the amount of vitreous removed overall. Removing less vitreous from the eye may lower the likelihood of postoperative hypotony. In addition, a pars plana approach facilitates the removal of retained lenticular material near the posterior capsule, iris, and ciliary body and thus lessens the chance of secondary inflammation and cystoid macular edema.3
Because the procedure is performed in a closed chamber, reduced intraocular turbulence minimizes IOP fluctuations and lessens the risk of suprachoroidal hemorrhage.4 Furthermore, pars plana vitrectomy reduces corneal edema that occurs secondary to trauma from anterior vitrectomy performed through a phaco incision.
According to Chalam and Shah,3 96.5% of eyes studied achieved a BCVA ≥ 20/40. Furthermore, 72.4% achieved a BCVA ≥ 20/20 postoperatively at 3 months. Vitreous loss with posterior capsular rupture occurred in all eyes, and cystoid macular edema was noted in two (6.8%) eyes. These results compare favorably with those of cataract surgery in which no vitreous loss is noted or anterior vitrectomy is used for complicated cataract surgery.2 Thus, pars plana vitrectomy seems to be a promising alternative in treating vitreous loss.
Retinal tears or detachment due to increased forward traction on the retina can occur during vitreous loss. Furthermore, lifting and removing lenticular material with pars plana vitrectomy can increase the risk of a retinal break. A surgeon who performs pars plana vitrectomy should routinely examine the retina with scleral depression to identify possible retinal breaks, and he must have resources readily available to treat any retinal disorder that may be present.
According to Chalam and Shah,3 pars plana anterior vitrectomy was not used in eyes with visually significant posterior segment pathology, in monocular patients, or in eyes with a nucleus that dropped into the posterior segment. Thus, the successful application of pars plana vitrectomy for treating vitreous loss may be overestimated, because its use was limited to patients without significant eye pathology. The sutureless method may also be prone to wound dehiscence and lead to postoperative hypotony. Any large sclerotomy site from pars plana vitrectomy can lead to complications, including vitreous incarceration, injury to the ciliary body, retinal dialysis, and wound dehiscence. It is advisable to consider suturing the sclerotomy site after pars plana vitrectomy to ensure wound closure.
The pars plana approach may have limitations in completely removing vitreous from the anterior chamber. The irrigation system may not sufficiently push back strands of vitreous. Thus, the surgeon may still need to perform additional cleanup with vitrectomy through the anterior phaco incision after pars plana vitrectomy. With this in mind, the pars plana approach may occasionally be more cumbersome and time consuming.
With proper surgical technique and experience, the anterior segment surgeon can effectively manage vitreous loss during phacoemulsification cataract surgery by employing pars plana anterior vitrectomy. This method may provide greater accessibility, less vitreous loss, and more favorable visual outcomes compared with current practices. However, one must exercise extreme caution in preventing secondary complications such as retinal tears or hypotony. Furthermore, published studies on pars plana anterior vitrectomies for the management of vitreous loss are currently limited, and most reports on the technique's visual outcomes and success to date have been largely anecdotal.4,5 Larger, prospective studies with long-term outcomes must evaluate the true efficacy and safety of this procedure.
Patty Lin, MD, MBA, may be reached at (310) 825-5000; firstname.lastname@example.org.
Y. Ralph Chu, MD, is Medical Director, Chu Vision Institute in Edina, Minnesota. He may be reached at (952) 835-1235; email@example.com.
Nina Goyal, MD, is a resident in ophthalmology at the Rush University Medical Center in Chicago. She may be reached at (312) 942-5315; firstname.lastname@example.org.
Wei Jiang, MD, is a resident in ophthalmology at the Jules Stein Eye Institute in Los Angeles. She may be reached at (310) 825-5000; email@example.com.
Baseer Khan, MD, is a senior resident in ophthalmology in the Department of Ophthalmology at the University of Toronto. He may be reached at (415) 258-8211; firstname.lastname@example.org.
Gregory J. McCormick, MD, is a cornea and refractive fellow at the University of Rochester Eye Institute in New York. He may be reached at (585) 256-2569; email@example.com.
Jay S. Pepose, MD, PhD, is Professor of Clinical Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis. He may be reached at (636) 728-0111; firstname.lastname@example.org.
Paul Sanghera, MD, is a resident in ophthalmology in the Department of Ophthalmology and Vision Sciences at the University of Toronto. He may be reached at (416) 666-7115; email@example.com.
Renée Solomon, MD, is an ophthalmology fellow at Ophthalmic Consultants of Long Island in New York. She may be reached at firstname.lastname@example.org.
Tracy Swartz, OD, MS, may be reached at (615) 321-8881; email@example.com.
Ming Wang, MD, PhD, may be reached at (615) 321-8881; firstname.lastname@example.org.