EyeWorld Asia Pacific is the news and feature magazine of APACRS, KSCRS, and COS. EyeWorld Asia-Pacific serves as the premier publication for anterior segment surgeons in the Asia-Pacific region.
Issue link: http://digital.eyeworldap.org/i/766530
60 EWAP DEVICES December 2016 by Michelle Dalton EyeWorld Contributing Writer Today's corneal topographers Some skeptics claim tomography has more benefits than topography, but both are needed in anterior segment surgery T hanks to technological advances, physicians are able to image the entire cornea, including the anterior and posterior cornea. Most topographers are Placido- based devices that primarily image the anterior surface of the cornea, whereas tomography refers to Scheimpflug-based devices and some optical coherence tomography (OCT) devices that become a 3D reconstruction of the anterior segment. Topography as used today was introduced in the 1980s, and Stephen Klyce, PhD, is largely credited with developing the maps produced that are derived from numerous points on the cornea. 1 Placido-based devices will also show tear film abnormalities, which Scheimpflug-based systems do not. The Placido- based devices have been shown to be as accurate in IOL power calculations on their own as automated keratometry or as a combined Placido-based and dual Scheimpflug corneal topographer. 2 The data these devices provide must be extrapolated to determine anterior and posterior elevation and pachymetry, whereas the Scheimpflug systems do not directly assess corneal curvatures. Some experts think topography is limited in that it can only image one surface of the cornea and only about 60% of that surface (that of the central cornea), and that tomography and OCT provide images from limbus-to-limbus and have full pachymetry maps as well. Yet others think both topography and tomography are necessary in any burgeoning high-volume anterior segment practice. Corneal topography became an integral part of refractive surgery screening, known for its sensitivity for detecting subtle changes on the anterior corneal surface secondary to ectatic disorders. 3 Here we provide an update from the manufacturers on the various topography systems currently available. Atlas 9000 Corneal Topography System The Atlas 9000 Corneal Topography System (Carl Zeiss Meditec, Jena, Germany) has a patented alignment system, and its ability to analyze multiple images during the alignment phase means it will automatically select the highest quality image. A software element streamlines gas permeable contact lens fittings as well as other difficult and specialty lenses. By using its proprietary "cone of focus" alignment system, the Atlas is said to deliver sub-micron elevation accuracy. The company touts the 22-ring Placido disk as being optimized to avoid ring crossover, resulting in more reliable results for a wide range of patients. In addition, its corneal analysis software anterior topographic screening tool assists with refractive surgery screening and helps identify abnormal corneal conditions for monitoring and follow-up. The device's corneal wavefront analysis "takes corneal topography to a new dimension. Using ray tracing technology, the Atlas displays higher-order corneal aberrations, providing valuable insight for patient education and treatment planning." Plus, by measuring the pupil size at both scotopic and photopic illuminations, the device can provide insight into optical zones under varying light conditions. iTrace The iTrace Ray Tracing Wavefront Aberrometer and Corneal Topography (Tracey Technologies, Houston) "sequentially projects 256 near- infrared laser beams into the eye to measure forward aberrations, processing data point-by-point. This 5-in-1 system provides auto- refraction, corneal topography, ray tracing aberrometry, pupillometry and auto-keratometry." By adding wavefront aberrometry to corneal topography, the company claims a "unique analysis" that isolates the internal aberrations of the eye by subtracting the corneal aberrations from the total aberrations. OPD-Scan III The OPD-Scan III (Nidek, Gamagori, Japan) combines wavefront aberrometer, topography, auto-refractometer, auto-keratometer, and pupillometer/pupillographer into one refractive workstation. This device separates the total, corneal, and internal component continued on page 64 Pentacam AXL In February, Oculus Optikgeräte (Wetzlar, Germany) announced that its new Pentacam AXL had received 510(k) clearance from the U.S. Food and Drug Administration (FDA). The company called the device "a systematic enhancement of the time-tested Pentacam HR". The device upgrades the Pentacam HR with axial length measurement, which will allow surgeons to make accurate IOL calculations, according to the company's website. Galilei G6 Pending FDA approval, the Galilei G6 (Ziemer Ophthalmic Systems AG, Port, Switzerland) promises to be "the most complete all-in-one solution, from refractive to cataract surgery". The system combines Placido topography, optical biometry measuring both axial and intraocular distances in one exam session, and dual Scheimpflug tomography offering 3D chamber analysis and ray-traced posterior corneal surface data in one device. The company says that the applications of the device will include premium IOL selection, corneal incision planning, IOLs for post-refractive cases, and topographic screening. Topcon CA-800, KR1W According to Topcon (Tokyo), its CA-800 Corneal Analyzer is an "easy-to- use, comprehensive corneal topography solution allowing for the complete evaluation of the anterior corneal surface." Meanwhile, the KR-1W is touted as "the only wavefront & topography system to offer both refractive and diagnostic functionalities." The device can be used for wavefront aberration, corneal topography, pupillometry, keratometry, and auto-refraction.