EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/194331
October 2013 EW CATARACT 39 Parabulbar anesthesia – Anterior subTenon's anesthesia is safe and effective by Scott Greenbaum, MD I n 1992, Julian Stevens, FRCS, reported on the use of subTenon's anesthesia for cataract surgery in the U.K.,1 and I reported on my experience in the U.S.2 The two reports differed in more than geography. The cannula Dr. Stevens used was long enough to directly deliver anesthesia to the posterior surface of the globe. My technique employed a short cannula that delivered anesthesia to the region of the equator, employing hydraulic dissection of the subTenon's space to spread anesthesia posteriorly. The goal of achieving retrobulbar quality anesthesia without retrobulbar complications drove the development of both techniques. However, the blind introduction of a blunt metal cannula posteriorly carries with it the same, albeit reduced in frequency and perhaps severity, complications. Restrictive diplopia following posterior sub-Tenon's anesthesia has been described.3 Likewise, optic nerve trauma and even globe perforation have been described and summarized in a 2011 paper titled, "Sub-Tenon's anaesthesia complications and their prevention." The authors concluded, "It is surmised, although not proven, that a shorter, less rigid or flexible cannula, and lower volume of local anaesthetic agent can improve the safety profile of sub-Tenon's block."4 Despite the safety drawback in using a long metal cannula, posterior sub-Tenon's anesthesia took off in the U.K. during the past two decades, while safer parabulbar anesthesia smoldered in the U.S. In 2009, the "Cataract National Dataset Electronic Multicentre Audit of 55,567 Operations: Anaesthetic Techniques and Complications," a major study of cataract surgery anesthesia in the U.K., was published. It revealed that posterior sub-Tenon's anesthesia had become the most used form of cataract anesthesia, at an average prevalence of 47%.5 While in the U.S., the Leaming survey, conducted for the 2012 ASCRS•ASOA Symposium & Congress, revealed a 2.9% use of sub-Tenon's anesthesia in the U.S., with a 78% use of some form of topical anesthesia. Leaming did not specify cannula length. He did, however, break down the numbers by surgical volume. It is interesting to note that among surgeons doing three to 75 cases a week, the use of sub-Tenon's anesthesia is more than double the average, with no surgeons doing two or less or 76 or more utilizing sub-Tenon's. While the former is related to surgeon training, clearly the latter is due to anesthetic personnel training. The reluctance of American ophthalmic anesthesiologists and Certified Nurse Anesthetists to create a snip in the conjunctiva/subTenon's tissue just posterior to the limbus has limited the growth of parabulbar anesthesia in the U.S. in a way not seen in the U.K., where in the early 1990s most anesthesiologists were employing general anesthesia for cataract surgery. Sub-Tenon's was regarded as a less invasive and faster technique there, accounting for its widespread growth. In the U.S., Richard Fichman, MD, and others began to popularize topical anesthesia, which caught on for the same reasons. While the speed of topical anesthesia equals parabulbar, does the quality? In a study of 20,000 surgeries studied over a two-year period, the Study of Medical Testing for Cataract Surgery Study Team reported in 2000 that compared with topical anesthesia alone, reports of any pain during surgery were always less with anesthesia by injection, but side effects with any additional agents were always more than without these agents. However, topical anesthesia with sedatives and opioids compared favorably with anesthesia with injection strategies with respect to pain and side effects. The anesthesia strategy with the lowest report of any pain during surgery (1.3%), dissatisfaction with pain management (1.9%), drowsiness (9.6%), and nausea, vomiting, or both (1.5%) occurring after surgery was anesthesia with injection with sedatives and diphenhydramine. This strategy was comparable with topical anesthesia alone with regard to side effects, but reports of any pain during surgery were much less.6 One year later a study that elimicontinued on page 40 How continued from page 38 gical microscope is difficult, such as in white cataracts. Interestingly, since starting with the femtosecond laser in December 2012, I personally have not used capsular dye. An even more common situation is the use of the femtosecond laser for patients with dense cataracts. It appears that most of the femtosecond lasers can image relatively dense cataracts. By fragmenting a dense cataract, the phaco procedure can switch from a somewhat challenging case to a relatively easy case. More importantly, laser fragmentation of a dense cataract can allow for reduced phaco energy, resulting in less inflammation and corneal edema postoperatively. In summary, femtosecond laser-assisted cataract surgery is fast becoming an integral part of the treatment of challenging cataract surgery patients. While the technology cannot image through exceptionally small pupils, there are The femtosecond laser creating a 4.5 mm circular capsulorhexis along with eight pie cuts with one cylinder cut into a cataract in an eye with a 5.0 mm pupil Source (all): William Trattler, MD techniques available to dilate the pupil prior to performing the femtosecond laser portion of the procedure. In cases where the pupil is just large enough to perform femto laser surgery, I have found that this technology has been very effective at making the cataract surgery safer for my patients with faster visual recovery. I expect with further iterations and improvements that the femto laser will be able to treat even smaller pupil cases and will continue to be utilized by surgeons for challenging cataract surgical procedures. EW Editors' note: Dr. Trattler is director of cornea, Center for Excellence in Eye Care, Miami. He has financial interests with LENSAR and Abbott Medical Optics (Santa Ana, Calif.). Contact information Trattler: 305-598-2020, wtrattler@gmail.com