Cover Feature: Challenging cataract cases
November 2008
by Maxine Lipner
Senior EyeWorld Contributing Editor
How to best help this complex breed of cataract patients
The patient in your chair is not a run of the mill cataract candidate. He or she has previously undergone a vitrectomy. What does that mean for you? What type of complications may loom large here? While the surgery is not as complex as it once was it still has its particular considerations and idiosyncrasies, according to Louis D. “Skip” Nichamin, M.D., medical director, Laurel Eye Clinic, Brookville, Pa. “Years ago we did not have as refined a procedure and especially equipment so it was a little more challenging,” he said. “But today we understand the vitrectomized eye better and we can compensate for the changes that are induced from the surgery and the techniques and equipment are better.”
The fact is the need for cataract surgery is likely all too common in the vitrectomized eye, according to Diana V. Do, M.D., assistant professor of ophthalmology, Wilmer Eye Institute, John’s Hopkins University, School of Medicine, Baltimore. “Most studies have said that there is an incidence of cataract of from 6 to 100% after vitrectomy surgery,” Dr. Do said.
Souce: Louis D. “Skip” Nichamin, M.D.
Treading carefully
These patients cannot be treated like those with “virgin” eyes, Dr. Do believes. “We think that it’s safe to do phacoemulsification, but there may be some considerations that the cataract surgeon may want to take into account,” she said. “For instance, when the vitreous is removed during vitrectomy surgery the posterior capsule may become more mobile during phacoemulsification and the cataract surgeon may have to be more aware of this to avoid a capsular rupture in order to place the IOL safely in the posterior capsule bag.”
She recommends extra caution during the actual phacoemulsification procedure in such cases. “When removing the cataract and when most of the nucleus is removed and now they’re removing more cortical material, I think that using a lower level of aspiration or vacuum might be beneficial.”
Dr. Nichamin agrees that extra care is needed in these cases. “As soon as one enters the eye the cataract surgeon is aware of an unusual deepening of the anterior chamber because the vitreous cavity is now fluid filled as opposed to having a semi-solid viscous vitreous back there,” he said. One way to compensate for that is with use of a retrobulbar block. “By doing a retrobulbar or peribulbar injection you actually increase the volume around the eye within the orbit,” Dr. Nichamin said. “That actually negates some of the problem with increased space.” He finds that it creates some positive vitreous pressure that actually keeps things up in the eye. “So, that sudden deepening is compensated someway by the increased external ocular pressure.”
He does offer a word of caution for those who opt for intracameral lidocaine in these cases. “We discovered in our early topical and intracameral experience that when you inject lidocaine into the eye in these post-vitrectomized cases that the patient can’t see for a period of time,” Dr. Nichamin said. “It causes temporary amaurosis. It puts the retina to sleep.” This is something that wears off with time but that practitioners should be aware of with these patients.
During the procedure itself Dr. Nichamin recommends that practitioners be methodical. “First things first—we don’t over deepen the anterior chamber with viscoelastic when we perform the capsulorrhexis,” he said. “Then when we switch over to infusion we need to lower the bottle if the volume of fluid needs to be controlled.”
Like Dr. Do, he also suggests judicious use of phaco power. “We tend to work at slower fluidic settings to avoid turbulence,” Dr. Nichamin said. “Also, we need very water tight incisions, which we always advocate in cataract surgery but which becomes particularly important when we have a less stable intraocular environment post-vitrectomy.”
Besides the deeper chamber and fluidic challenges, Dr. Nichamin finds that the other main consideration is the potential for zonular weakness. “Often there can be mild to even moderate compromise of the zonular capsular integrity of vitrectomy surgery,” Dr. Nichamin said. “So, the surgeon always has to be on guard for the possibility of an unexpected weakened zonular membrane or, zonular dehiscence or, even a small opening of the posterior capsule.” This could become evident as early as during hydro-dissection. As a result, hydro-dissection needs to be done meticulously yet carefully. “You have to do things gently but thoroughly,” Dr. Nichamin said. “You end up often times walking on egg shells and tippy toeing through the surgery in these types of eyes.”
Retinal reminders
Practitioners must also keep in mind that these are patients who are already predisposed to retinal problems. As a result, Dr. Nichamin recommends keeping a close watch for cystoid macular edema (CME). “All of these eyes, I believe need to be prophylaxed and treated postoperatively as well with non-steroidal anti-inflammatories and probably a more aggressive steroid treatment than normal,” he said. “Secondly, postoperatively these eyes have got to be examined carefully to make sure that there aren’t new or open retinal tears that need to be addressed.”
Predisposition to retinal problems also means careful IOL selection. With this in mind, Dr. Nichamin usually avoids silicone IOLs. “We’ve known for years that silicone as a material can be problematic if the patient requires either an air fluid exchange or silicone oil injection, because the interface becomes very difficult to view through,” he said. “So, for most of these patients who have significant vitreoretinal disease we would prefer to have an acrylic implant.” In these cases, Dr. Nichamin also avoids multifocal optics. “They decrease contrast sensitivity for both the patient and the surgeon,” he said. “You want to optimize the view of the peripheral fundus, so you want to use and optic dimension and design that allows us to do that.”
Dr. Nichamin currently uses the early style three-piece acrylic MA 60 (Alcon, Fort Worth, Texas) for such patients. “What is different about their acrylic as opposed to say the Sensar acrylic (Advanced Medical Optics, Santa Ana, Calif.) is that it’s tackier and in the anterior capsule in particular it remains very clear,” he said. “So, that the peripheral anterior capsular rim is still transparent and one can view and treat peripheral retinal pathology optimally.” Underlying retinal pathology can also affect outcomes reminds Dr. Do. “Visual acuity improvement after cataract in an eye with retinal pathology may be different,” she said. “So, the outcomes may not be as good because of the underplaying retinal disorder.” She urges practitioners to be sure that they clearly explain this to the patient before performing the procedure. “Patients need to have the correct expectation going into surgery,” she said.
Currently there is no definitive investigation trail to follow to predict outcomes following cataract surgery for this population. “There is no large prospective study that has looked at outcomes after cataract surgery in vitrectomized eyes,” Dr. Do said. She herself along with fellow investigators recently performed an extensive review of all of the medical literature to look at the safety of cataract surgery in vitrectomized eyes. In the study published in July 16, 2008 issue of Cochrane Database of Systematic Reviews, investigators searched 1949 articles and found that there was no randomized study that could give any information on outcomes in these cases. “Most of what is out there is limited to retrospective case reports and those have some inherent biases,” she said. “So, right now we can’t give a firm statistic to patients who are in this clinical scenario.”
Overall, with this in mind, she urges practitioners to watch this group more closely. “We can say that the majority of cataract surgeries are safe and have good outcomes, but those patients who have undergone vitrectomy may need to have closer postoperative follow up,” Dr. Do said. “Patients need to be more aware of the potential risk of surgery and the limitations of the procedure related to their vision.”
Editors’ note
Drs. Nichamin and Dr. Do have no financial interests related to their comments.
Contact Information
Do: 410-614-6908, ddo@jhmi.edu
Nichamin: 814-849-8344, Nichamin@laureleye.com
