EyeWorld Asia-Pacific June 2011 Issue

June 2011 19 EW FEATURE AT A GLANCE • When it comes to managing astigmatism at the time of cataract surgery, most doctors prefer to use a toric implant and then LRI as a second choice • Some doctors don’t believe in LRIs because they think that they regress and are unpredictable. However, there is 10- to 15-year data that shows how well these work, but it is a specific surgical technique that one cannot take too lightly. It has to be done properly • When implanting a patient with a multifocal lens, surgeons manage the astigmatism with LRIs. Additionally, in cases of high astigmatism where a patient’s astigmatism exceeds the power of the toric lens, LRI is combined with toric lens implantation • The main points when performing LRIs are careful positioning, careful placement, and careful measurement such that one obtains accurate depth incisions with a high- quality diamond. If all of that is adhered to, the results of LRIs are excellent Laurence SULLIVAN, MBBS, FRANZCO LaserSight and Bayside Eye Specialists 2/1CO Victoria Parade, East Melbourne, Victoria 3002, Australia Tel. no. +613-95967440 Fax no. +613-95967449 Laurence.sullivan@gmail.com Toric lenses over the past few years have gained a huge place in my practice such that I now use them in all patients with more than 0.75 diopters of preexisting corneal astigmatism. Prior to the availability of toric lenses, I was a regular user of limbal relaxing incisions (LRIs). I still use astigmatic keratotomy (AK) incisions in patients with extreme corneal astigmatism following corneal transplantation but have found surface laser vision correction to be effective in these patients as well. Currently about 40% of my patients obtain the benefits of toric IOLs and an analysis of my own results for a consecutive cohort of fifty patients demonstrated a decrease in preoperative corneal astigmatism from 1.67±1.30 diopters to a postoperative refractive astigmatism of 0.23±0.29 diopters. This level of predictability and accuracy was really unattainable with the use of limbal relaxing incisions, although these could be simply repeated or augmented at the slit lamp postoperatively if needed. Toric lenses may be a little bit less accurate in the setting of forme fruste keratoconus where the keratometric and refractive astigmatism may not align perfectly. In the case of postoperative error in these patients, it is possible to use calculations based on crossed cylinder formulas to calculate the postoperative adjustment to the IOL axis which is required to minimize astigmatism. I have found this useful in a few cases. 1 Some surgeons suggest that LRIs be used when implanting multifocal IOLs with preexisting corneal astigmatism and again my results and experience from the last few years of using toric IOLs would suggest that a toric multifocal IOL such as Zeiss (Dublin, Calif., USA/Jena, Germany) produce would give a more reliable refractive result. Incisional surgery to decrease postoperative astigmatism is still a possible consideration, as is laser vision correction. In all, I have found toric IOLs to be the greatest advancement in refractive cataract surgery in the last decade and they have really relegated LRI, in my hands at least, to very much a secondary option. Reference 1. Tseng SS, Ma JJ. Calculating the optimal rotation of a misaligned toric intraocular lens. Cataract Refract Surg. 2008 Oct;34(10):1767-72. Editors’ note: Dr. Sullivan has no financial interests related to his comments. appreciated approach, Dr. Nichamin said. The LRI is typically performed at the beginning of surgery prior to phacoemulsification and IOL implantation, except in one situation where the phaco incision is superimposed with the LRI, he said. In that situation, he doesn’t create a long LRI, just a short initial one, and then he extends it at the end of surgery to prevent wound gape. Dr. Nichamin said his technique is more detailed than others who might take a low- down and simple approach. He measures at the limbus and uses an adjustable, high-quality diamond blade and sets the blade based on the thickness of the tissue. “We take all of our measurements—the astigmatism, the location, the amount, as well as the corneal tissue—very carefully, and we labor over the exact location of these incisions,” Dr. Nichamin said. Specifically, the incisions are not actually in the limbus; they’re just inside of it, still in the peripheral clear corneal, he said. The main points he teaches are careful positioning, careful placement, and careful measurement such that one obtains accurate depth incisions with a high-quality diamond. “If all of that is adhered to, the results of LRIs are excellent,” he said. The LRI is a technique that any good surgeon can master, Dr. Holland said. One of his tips includes setting the diamond blade to 550 microns. He also recommended getting one of the available nomograms because the length of incision and whether a surgeon uses one or two incisions is based on the age of the patient, the axis of astigmatism, and the magnitude of astigmatism. There are plenty of nomograms available that a surgeon could use to guide him or her, Dr. Holland said. According to Mark Packer, MD, clinical associate professor of ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, Ore., USA, his results using the ORange Aberrometer (WaveTec Vision Systems, Aliso Viejo, Calif., USA) to measure and enhance his relaxing incisions as needed are similar to results with the toric intraocular lens up to about 2.5 D of corneal astigmatism. Beyond that, he said, it becomes difficult to achieve the full effect a surgeon may want with a relaxing incision. Contraindications As with many procedures, there are patients for whom performing an LRI is not advisable. These include patients with limbal peripheral corneal pathology, extreme dry eye, particularly associated with rheumatoid disease, and those who have had radial keratotomy and astigmatic keratotomy, Dr. Nichamin said. For the later two, additional surgery becomes dangerous and in that situation, he would prefer using a toric IOL. In addition, Dr. Holland said he would not recommend LRIs in patients with asymmetric astigmatism, for instance, mild inferior steepening that might be seen in forme fruste keratoconus. In such a case, Dr. Holland said, “I don’t think it’s a choice, I’d much prefer a toric lens to an LRI.” EW Editors’ note: Drs. Holland and Nichamin have no financial interests related to their comments. Dr. Packer has a financial interest in WaveTec Vision Systems. Contact information Holland: 859-331-9000, eholland@holvision.com Nichamin: 814-849-8344, nichamin@laureleye.com Packer: 541-687-2110, mpacker@finemd.com