EyeWorld Asia-Pacific December 2018 Issue

O CULUS (Wetzlar, Germany) hosted a lunch symposium at the 31st APACRS An- nual Meeting in Chiang Mai, Thailand, on 19 July 2018. The symposium introduced updates to the company’s Corvis ST and Pentacam AXL platforms designed to enhance the safety and efficacy of refractive surgery. Michael Belin, MD , began by discussing “Clinical applications of the Belin ABCD Progression Display.” Dr. Belin compared the current approach to the evaluation of patients with keratoconus to what is called an “idiot light” in the automotive indus- try—an indicator that by the time its alarm goes off is already too late. This is particularly the case, he said, when using Kmax. “If you get changes on the anterior surface, you get changes in Kmax, it means your refracting surface is already compromised,” Dr. Belin said. Rather than an idiot light, what is needed is a way to monitor progres- sion and see changes to the cornea early, not when it has already started decreasing vision. This is particularly relevant ow- ing to advances in the management of keratoconus. Whereas until recently the two treatments had been penetrat- ing keratoplasty and rigid contact lenses, used only when the severity of the disease had created anterior surface changes, these days we have crosslinking, a treatment that requires identification and characterization of the disease as early as possible— before the patient has loss of vision. Previously, Dr. Belin had devel- oped the Belin-Ambrosio Display, which uses an enhanced reference surface that is normalized by remov- ing a 3-mm exclusion zone centered on the thinnest point of the cornea from analysis. However, to characterize the disease, Dr. Belin said that rather than removing the exclusion zone, “let’s actually look at that zone.” Dr. Belin developed a new clas- sification called the ABCD classifica- tion: A for anterior radius curvature at the thinnest point (not the apex); B for “back” or posterior radius cur- vature at the thinnest point; C for cor- neal thickness at the thinnest point; and D for distance visual acuity. Biomechanics meets tomography. Corvis ST meets Pentacam AXL Supplement to EyeWorld Asia-Pacific Winter 2019 APACRS The classification system consist- ed of five stages, adding a stage 0 to the old Amsler-Krumeich classification (Figure 1). Using this system, each layer is graded independently. The system is currently available on the Pentacam as part of the Topo- metric Keratoconic Staging Display. The goal of the classification system was to develop a way to determine when and if true progres- sion occurs. What Dr. Belin and his colleagues have come up with is the ABCD Progression Display. The display shows up to eight exams over time, analyzes the ABCD parameters and displays both 80% and 95% one- sided confidence intervals. “If you seek statistically signifi- cant change here, it’s an indication to treat in spite of the fact that the patient retains good vision,” Dr. Belin said. “We should not be waiting until loss of vision occurs. We should be looking for true progression and inter- vening at the earliest possible stage.” The tomography-based progres- sion display documents statistically significant change and allows timely crosslinking, also showing crosslink- ing efficacy. In his talk, Fritz Hengerer, MD , discussed “Patient screening and IOL calculation with Pentacam AXL and Keratograph 5M,” providing an over- view of what they do in Heidelberg with their IOL patients. For preoperative cataract screen- ing, Dr. Hengerer performs ocular sur- face analysis with the Keratograph 5M (OCULUS) before Pentacam analysis. Measurements are taken before any eye drops are applied. The Keratograph can demonstrate diminished tear breakup time despite a normal looking slit lamp corneal reflex and can be used to help patients understand the need for steroid treatment to manage postop dry eye. Meanwhile, the Pentacam—originally named for measuring five param- eters—measures various parameters including axial length, keratometry, pachymetry, pupil diameter, natu- ral lens densitometry, keratoconus screening, index reporting, and IOL calculation. Prof. Naoyuki Maeda established an algorithm to develop preop assess- ment of corneal optical properties for premium IOL selection using four-step criteria on the Pentacam’s Cataract Preop Display: (1) evaluation of HOAs; (2) corneal shape assessment; (3) eval- uation of corneal spherical aberrations (Z4,0); and (4) evaluation of corneal astigmatism, including magnitude and axis. “With the latest software update of the Pentacam AXL, we can assume that it is faster, the measurements are more precise, can measure denser cataracts,” Dr. Hengerer said. Furthermore, he said, the soft- ware makes it feasible to compare with the IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany), which uses a completely different approach to evaluating the cornea. Heidelberg University undertook a large comparative prospective trial comparing the IOLMaster 700 and Pentacam AXL using the most recent software versions of both devices. Evaluating 158 eyes from patients who fulfilled inclusion criteria and consented and who underwent three exams per eye with the IOLMaster 700 and Pentacam AXL, Dr. Hengerer and his colleagues looked at: (1) success rate of axial length measurements— quality scan = OK for the Pentacam, no exclamation mark for the IOLMas- ter; (2) comparison of three repeated exams taken with both devices for the same eye regarding repetition of axial length, keratometry, astigmatism and axis, anterior chamber depth, horizontal corneal diameter (HWTW); (3) coefficient of repeatability, the standard deviation and mean. Dr. Hengerer and his colleagues found that the Pentacam AXL had a higher success rate for axial length measurements (Figure 2), with higher repeatability for axial length, keratom- etry, astigmatism, axis, and HWTW measurements. The IOLMaster, on the e news magazine of the Asia-Paci c Association of Cataract & Refractive Surgeons New Belin ABCD keratoconus classification/grading ABCD criteria A B C D ARC (3 mm zone) PRC (3 mm zone) Thinnest pach um BDVA Scarring STAGE 0 > 7.25 mm (< 46.5 D) > 5.90 mm > 490 um ≥ 20/20 (≥ 1.0) - STAGE I > 7.05 mm (< 48.0 D) > 5.70 mm > 450 um < 20/20 (< 1.0) -, +, ++ STAGE II > 6.35 mm (< 53.0 D) > 5.15 mm > 400 um < 20/40 (< 0.5) -, +, ++ STAGE III > 6.15 mm (< 55.0 D) > 4.95 mm > 300 um < 20/100 (< 0.2) -, +, ++ STAGE IV < 6.15 mm (> 55.0 D) < 4.95 mm ≤ 300 um < 20/400 (< 0.05) -, +, ++ Figure 1. New Belin classification system Source: Michael Belin, MD Axial length [mm] n [%] Mean Min Max COR Max. diff 1. vs 3. exam Max. diff 1. vs. 2. exam Max. diff 2. vs. 3. exam IOLMaster 700 117 72,84 23,41 21,02 28,11 0,027 0,08 0,07 0,071 Pentacam AXL 128 80,5 23,6 20,988 34,17 0,022 0,051 0,078 0,078 IOLMaster 700, inkl. (!) 156 98,11 23,74 21,02 34,2 0,050 0,3 0,3 0,1 Figure 2. Comparison of success rates between the IOLMaster and Pentacam AXL for axial length measurements Source: Fritz Hengerer, MD Sponsored by OCULUS Optikgeräte GmbH