EyeWorld Asia-Pacific September 2015 Issue

3 EWAP EDITORIAL September 2015 Letter from the Editor Dear Friends T he current edition of EyeWorld Asia-Pacific touches on several new technologies, including femtosecond cataract surgery and multifocal and toric IOLs. The uptake of toric IOLs has been far greater than multifocal IOLs and femtosecond cataract surgery. The improved refractive outcome with toric IOLs is immediately evident, in contrast with femto laser-assisted cataract surgery where the evidence for is still lacking. In order to obtain the maximum benefit with toric IOLs, however, surgeons have to consider the most appropriate instruments to measure astigmatism, methods to predict the appropriate toric cylinder power and axis, and techniques to ensure accurate alignment of the toric implant. In addition to optical biometers, topography is essential in interpreting astigmatic measurements prior to surgery. Personally, I recommend a third instrument be considered as this is helpful if the primary instruments such as the biometer and topography provide different results. In these situations considering the astigmatic correction in a patient’s spectacles can be helpful in deciding the most appropriate keratometry values to be used to predict the required toric intraocular lens. There are several methods available to calculate the required toric lens. Most surgeons in this issue recognize the importance of considering the posterior cornea and using a method which takes this into account. Our ability to align a toric lens accurately is facilitated by new technologies such as image-guided technology and intraoperative aberrometry. Personally, I use an app I developed for the iPhone to accurately determine the true orientation of the reference axis to ensure accurate marking. There are many different toric intraocular lenses and rotational stability is influenced by both the design and material of the intraocular lens. Despite the focus on toric lens alignment, inherent variability in surgically induced astigmatism plays a large role in unexpected outcomes with toric intraocular lenses. The magnitude of surgically induced astigmatism as determined by vector analysis is typically in the range of a half diopter. This value however does not consider the considerable variation in axis for individual cases and I would recommend the centroid value for surgically induced astigmatism is a more appropriate value to be entered in toric calculators. The centroid value is the mean of the summated individual vectors and typically in the range of 0.1 diopter for a 2.2- to 2.4-mm incision. Operating on a consistent axis and reducing incision size are also helpful in reducing the variability of surgically induced astigmatism with toric intraocular lenses. Although many surgeons still consider corneal incisions as an effective way to deal with preexisting astigmatism, it has been many years since I abandoned this approach as toric intraocular lenses are inherently more predictable. It is not uncommon for surgeons to reserve toric lenses for patients with higher levels of astigmatism but the benefit of toric lenses in patients with low astigmatism is equally important. In particular, patients with low levels of preexisting against-the-rule astigmatism, even in the half-diopter range can end up with 1 diopter or more of refractive astigmatism due to the role of the posterior cornea. These patients who were spectacle independent prior to surgery may end up requiring correction which can be a disappointing result. Low dioptric toric cylinders, however, do require careful attention to all the issues I have outlined and which are discussed at depth in this issue. I am sure that the use of toric intraocular lenses will continue to grow and I hope that the strategies and experience of the many surgeons who have contributed to this issue will help you achieve better outcomes. Warmest regards Graham Barrett Chief Medical Editor EyeWorld Asia-Pacific EYEWORLD ASIA-PACIFIC EDITORIAL BOARD C HIEF MEDICAL EDITOR Graham BARRETT, Australia MEMBERS Abhay VASAVADA, India ANG Chong Lye, Singapore CHAN Wing Kwong, Singapore CHEE Soon Phaik, Singapore Choun-Ki JOO, Korea Hiroko BISSEN-MIYAJIMA, Japan ASIA-PACIFIC CHINA EDITION Editors-in-Chief ZHAO Jialiang ZHAO Kan Xing Deputy Editor HE Shouzhi Assistant Editor ZHOU Qi ASIA-PACIFIC INDIA EDITION Regional Managing Editor S. NATARAJAN ASIA-PACIFIC KOREA EDITION Regional Editor-in-Chief Hungwon TCHAH Regional Managing Editor Chul Young CHOI Hungwon TCHAH, Korea John CHANG, Hong Kong Johan HUTAURUK, Indonesia Kimiya SHIMIZU, Japan Pannet PANGPUTHIPONG, Thailand Ronald YEOH, Singapore S. NATARAJAN, India Sri GANESH, India YAO Ke, China Y.C. LEE, Malaysia