EyeWorld Asia-Pacific September 2018 Issue

44 EWAP REFRACTIVE September 2018 Views from Asia-Paci c Hungwon TCHAH, MD Asan Medical Center, University of Ulsan 388-1 Pungnab-dong, Sonapa-fu, Seoul, South Korea Fax no. +82-2-4706440 hwtchah@amc.seoul.kr C orneal topography has improved tremendously over the past decade. Current corneal topography can provide important information such as corneal optical aberration, thickness, irregularity, regular and irregular astigmatism, the amount of anterior and posterior corneal astigmatism, and the tear distribution, depending on the model. Topography allows more accurate IOL power calculation in case of previous corneal refractive surgery patients and previous corneal transplantation patients on whom otherwise it is dif cult to estimate corneal curvature. Corneal topographical examination, also, shows what the slit lamp exam does not check, such as early basement membrane dystrophy and fruste forme keratoconus. So, corneal topographical assessment seems to be vital prior to cataract surgery, especially for premium IOL surgery to increase patient’s satisfaction. High corneal coma aberration, regular asymmetric corneal astigmatism and mildly irregular cornea, which otherwise are undetected without a corneal topographer, can be contraindications for multifocal IOL implantation. Information about the posterior corneal astigmatism also helps us to plan whether a toric or non-toric IOL will be suitable for the patient. In case of monofocal IOL implantation, a corneal topographer is bene cial to predicting the prognosis after cataract surgery by evaluating corneal status so that more detailed prediction for prognosis can be provided to a patient, which will increase the patient’s satisfaction and the rapport between the surgeon and patient. “ ...corneal topographical assessment seems to be vital prior to cataract surgery, especially for premium IOL surgery to increase patient’s satisfaction. ” - Hungwon Tchah, MD One thing to remember is that each topographer uses its own measuring technology, such as Placido ring, scanning slit lamp, Scheimp ug image, and LED dot refraction, as well as its own algorithm to analyze data. Thus, the results from each topographer may not be comparable. Understanding what technology your topographer is using and what your topographer is capable of and familiarization and customization of your own corneal topographic data are very important before using the topographer in order to improve the results of cataract surgery. Editors’ note: Dr. Tchah declared no relevant nancial interests. WANG Zheng, MD Professor, Aier School of Ophthalmology, Central South China University Aier Eye Hospital Group 191 Huanshi Zhong Road, Guangzhou, China gzstwang@gmail.com A s modern cataract surgery is becoming a refractive procedure, the status of corneal health has a great impact on the surgical outcome and postop patient satisfaction. This is especially true if a multifocal premium IOL is implanted. More and more cataract surgeons have realized the importance of corneal topography for preop evaluation. Corneal topography provides a lot of important information that may have in uence on the postop performance, such as the tear lm, corneal epithelium, regular or irregular astigmatism, angles alpha and kappa, etc. Keratoconus and other corneal disorders must be ruled out preoperatively, just like for any other refractive surgeries. As Dr. Dell said in the article, topography is also used for patient followup. “ Corneal tomography, which is often mixed up with topography by clinicians, provides even more information about the cornea, not only the anterior but also the posterior surface. ” - Wang Zheng, MD Corneal tomography, which is often mixed up with topography by clinicians, provides even more information about the cornea, not only the anterior but also the posterior surface. Theoretically, ray-tracing algorithms based on comprehensive data from the two surfaces of the cornea along with other ocular components may produce more accurate lens calculation. However, this technology is still under development and requires further clinical validation. One drawback of Scheimpflug tomography compared to Placido topography is that it is unable to assess the tear film. Therefore, both systems are necessary. While corneal topography is gradually becoming part of the routine pre-cataract surgery evaluation in developed countries, there are still many cataract surgeons who don't have adequate knowledge of corneal topography in China and many developing countries. I'm happy to see surgeons’ increasing awareness of the importance of corneal topography in cataract surgery. More surgeon education and training are needed. Editors’ note: Dr. Wang declared no relevant nancial interests. Diagnostics in refractive – from page 43