American Academy of Ophthalmology Web Site: www.aao.org
Clinical Update: Cataract
Burns, Leaks and Bugs: Preventing Incision Complications
As safe as cataract surgery is today, no surgery is completely risk-free. Three common incision-related complications - wound burns, leaks and infections - continue to occur and can have devastating results. Here are risk factors and tips for avoiding these problems, especially during this era of clear corneal incisions (CCIs).
Problem #1: Wound Burns
Phacoemulsification burns are "tough to study, as they're episodic," said Randall J. Olson, MD, chairman of ophthalmology at the University of Utah. Overall, the incidence of wound burns - defined as contracture with folds or whitening, increased astigmatism or difficulty sealing the wound - is approximately one in 1,000, Dr. Olson found in a survey of cataract surgeons in five Western states.1
Of 523 physicians contacted, 106 responded, providing data on 76,581 procedures and 75 wound burns. The following emerged as risk factors.
Technology. There is a "direct correlation between the risk of wound burns and how you use your power," Dr. Olson said. "The biggest risk, no surprise, comes with using continuous power."
Continuous ultrasound was associated with the highest incidence - 0.18 percent, or one in 550. At the other end of the spectrum, ultra- and hyperpulse technologies were associated with the lowest incidence - 0.026 percent, or one in 4,000. "That's a pretty good spread - about sevenfold," Dr. Olson noted. "Short pulses are very forgiving."
Technique. How you perform phaco also plays a role. Vertical chop turned out to be the safest technique, with three wound burns, or an incidence of one in 4,000. In contrast, divide and conquer was the riskiest approach, with 53 wound burns, or an incidence of one in 800.
Why would vertical chop make such a difference? This is where physician experience may play a role, Dr. Olson said.
While the study didn't have enough statistical power to evaluate physician experience as a separate factor, "vertical chop tends to be a more advanced technique and is used by more experienced people," he noted.
Tip occlusion. Of the 75 burns, 53 occurred during fragment removal, when tip occlusion is the goal. "When the tip is occluded with a tight wound, there can be a situation in which there is none to minimal flow; under these circumstances, temperature can very rapidly rise," Dr. Olson said. And because the ophthalmic viscous devices (OVDs) heat quickly and can promote a wound burn "in a matter of seconds," he noted, "it's important to aspirate a small amount of OVD so that there is free fluid flow before using ultrasound."
Problem #2: Wound Leaks
It's imperative that the wound is properly sealed at the end of surgery, to minimize the risk of infection. Indeed, "Whether it's a microleak or a gross leak, a leaky wound the day after surgery raised the risk of infection by 44 times in a study conducted at our institution," Dr. Olson said.2
This is especially important with CCIs. "Clear corneal incisions, by their nature, are less forgiving and more difficult to construct properly," said Samuel Masket, MD, clinical professor of ophthalmology at the University of California, Los Angeles, and in private practice in Century City. "But it's not mandatory that they will leak." Strategies to reduce the risk of leaks include the following:
Construct carefully. "CCIs should be square or nearly square in surface architecture," Dr. Masket said. "Incisions suffer when surgeons tend to force instruments or implants through them. You want to make the size of the CCI appropriate for the instrumentation."
Establish integrity. To ensure proper sealing, "It's important to check IOP at the close of surgery and establish it at physiologic levels," Dr. Masket recommended. "I also do an intraoperative Seidel test on every incision." Some research indicates that you can have wound leakage at low IOP,3 Dr. Masket said. "But in unpublished research, in cadaver eyes, I used a femtosecond laser to create different incisions. When properly constructed, there was no leakage."
And in a recently published study of 50 eyes - all with 2.2-mm unsutured CCIs - IOP was measured between two and six hours postoperatively, with readings ranging from 11 to 35 mmHg.4 "There was no ocular hypotony or wound leakage, and none of the eyes developed infection," Dr. Masket reported.
Consider sutures. "Remember that there is always the potential to suture if there are any questions regarding wound integrity," Dr. Masket said. Dr. Olson agreed. You're safest, he noted, if you have a "low threshold for putting a suture in and converting to an old-style incision."
Problem #3: Wound Infections
Although the estimate varies according to the study cited, the overall incidence of endophthalmitis following cataract surgery is approximately one in 1,000. And while some studies have found no correlation between a rise in endophthalmitis rates and the advent of CCIs, a special report on the subject notes that the bulk of the evidence suggests that there is a connection.3
Focus on basics. But as Dr. Masket pointed out, "What the report indicates is that CCIs are not all made the same or managed the same. The moral of the story is that CCIs do not, by necessity, have to be risk factors for leaks and endophthalmitis; but when poorly constructed and maintained, they can be. My sense is that it's all about wound construction, protection from stretch and intraoperative sealing."
Reconsider antibiotics. Dr. Olson noted, "Our study [of wound leaks and infections] also determined that antibiotics significantly reduce the risk of endophthalmitis, especially if they are used frequently the day of surgery, vs. the first postoperative day. I believe that heavy antibiosis the day of surgery, whether intracameral or topical - and we used topical - is prudent."
Another report on endophthalmitis and antibiotic prophylaxis cites recent research conducted in Europe, and lends significant support to the use of intracameral antibiotics at the conclusion of cataract surgery. In early data from a randomized, prospective study sponsored by the European Society of Cataract and Refractive Surgeons, the incidence of endophthalmitis in those who did not receive intracameral cefuroxime (Ceftin) was almost five times as high as the rate in those who were given the antibiotic.5 Because of these initial results, recruitment was halted early.
Another area of controversy, Dr. Olson noted, is the question of how long drops should be used. "I've always said a week, but some surgeons are seeing cases [of infection] coming back in during the second week." In fact, emerging research suggests that a second week of drops may be prudent, he said. "I'm changing my regimen based on this."
1 Bradley, M. J. and R. J. Olson. Am J Ophthalmol 2006;141:222-224.