EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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EW FEATURE 70 by Lauren Lipuma EyeWorld Staff Writer Poor pupillary dilation in one eye indicates a greater risk for zonular weakness on that side, as well as a shallow or deep anterior chamber or a depth that fluctuates based on patient position. Goniosco- py and ultrasound microscopy are useful techniques for assessing asymmetry of anterior chamber depth prior to surgery, Drs. Gedde and Giaconi said. Intraoperative management Poor pupillary dilation can be managed with mechanical pupil expanders, such as iris retractors or a Malyugin ring (MST, MicroSurgical Technology, Redmond, Wash.). Drs. Hart and Gedde prefer iris retractor hooks because they can be repositioned to the edge of the capsulorhexis to provide support for the capsule and counter tension for the capsulorhexis. "I like MST iris retractors for supporting the capsule because they're double-stranded, so the part that contacts the capsule is very smooth and won't break it," Dr. Hart said. Once the pupil has been sufficiently expanded, minimizing stress on the zonules is the main objective during surgery. "Avoid overfilling the eye with viscoelastic, as excessive deepening of the ante- rior chamber can place undue stress on the zonules," Dr. Gedde said. To prevent the mechanical stress of phaco from being transferred to the capsule or the zonules, Dr. Hart recommends fully hydrodissecting the lens so that it is spinning freely inside the capsule and using a chopping technique rather than divide-and-conquer. During cortex removal, Dr. Giaconi recommends stripping the cortex tangentially toward the area of weakness, rather than away from it, which will tear more zonules. Patients with zonular dialyses are also at risk for posterior fluid misdirection, said Dr. Gedde, which increases vitreous pressure and decreases the depth of the anterior chamber during surgery. "Use of a capsular tension ring, a lower irrigation rate, and a viscoelastic barrier in the area of zonular dialysis can serve to avoid this intra- operative complication," he said. Capsular tension rings Capsular tension rings (CTRs) are often used to manage zonular insta- bility in pseudoexfoliation patients, but surgeons differ in their opinions on whether or not to insert them universally in all pseudoexfoliation patients. Drs. Hart, Gedde, and Giaconi agreed that CTRs do not eliminate the risk of late dislocation, but do provide other intraoperative and postoperative advantages. Steven Gedde, MD, professor of ophthalmology, Bascom Palmer Eye Institute, Miami, stressed the importance of assessing for zonular weakness and poor pupil dilation preoperatively to guide intraoper- ative management. Iridodonesis, phacodonesis, asymmetry of anterior chamber depth, and lens subluxation are manifestations of zonular weakness, but these signs may or may not be present preoper- atively depending on the severity of the disease. Observing phacodonesis or lens subluxation at the slit lamp is a sign of severe zonular weakness, indi- cating that "all the zonules are near death or pretty much gone," said John Hart, MD, FACS, co-chief of anterior segment surgery, William Beaumont Hospital, West Bloomfield, Mich. In those cases, Drs. Hart and Gedde send the patient directly to a vitreoretinal specialist for a pars plana lensecto- my and vitrectomy with a sclerally fixated IOL. If zonular weakness is mild, signs of it can be subtle, but the fact that pseudoexfoliation tends to be asymmetric helps produce these signs, said JoAnn Giaconi, MD, associate clinical professor of ophthalmology, Jules Stein Eye Institute, Los Angeles. Cataract surgery in pseudoexfoliation syndrome cases Figure 1: Pseudoexfoliation material visible on the anterior lens capsule Figure 2: Close-up of Figure 1 Figure 3: Pseudoexfoliative material adherent to the corneal endothelium Unique challenges can be managed with the appropriate surgical tools and techniques, experts say T he deposition of extracellu- lar protein on the structures of the anterior segment puts patients with pseudo- exfoliation syndrome at a higher risk for complications both during and after cataract surgery. Zonular weakness, due to depo- sition of pseudoexfoliative material on the zonular fibers, and poor pupil dilation, due to infiltration of material into the iris stroma, are the factors that most increase patients' risk for complications. • If phacodonesis or lens subluxation is present at the slit lamp exam, experts recommend sending the patient to a retina specialist for pars plana vitrectomy and lensectomy. • Three-piece IOLs are easier to refix te than 1-piece IOLs. • Accommodating, toric, multifocal, and aspheric monofocal IOLs are contraindicated in patients with pseudoexfoliation. AT A GLANCE Complex cataract cases October 2014