Comparison of Central Corneal Thickness and Peripheral Corneal Thickness using Sheimpflug system, Optical Coherence Tomography and Ultrasound Pachymetry.

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<ul><li><p>Comparison of Central Corneal Thickness and Peripheral Corneal Thickness using Sheimpflug system, Optical Coherence Tomography and Ultrasound Pachymetry in Normal, Keratoconus and Post-Refractive Surgery Eyes at Different Corneal Thickness.Ricardo N. Sepulveda, MDClaudia Maria Prospero Ponce, MSKarolinne Maia Rocha, MD PhDWilliam J. Dupps, MD PhDRonald R. Krueger, MDCole Eye InstituteCleveland, OH*Authors have no financial interest.</p></li><li><p> l * l * Purpose: To compare central corneal thickness (CCT) and peripheral corneal thickness (PCT) with scheimpflug system (Pentacam), high-speed optical coherence tomography (Visante) and ultrasound pachymetry (US) in normal eyes, keratoconus suspect and post-laser in situ keratomileusis (LASIK).</p><p>Setting: Department of Refractive Surgery, Cole Eye Institute, The Cleveland Clinic. Cleveland, Ohio, USA.</p><p>Study Type: Retrospective AnalysisBackground</p><p> l * l * </p></li><li><p>IntroductionUltrasound pachymetry is currently the gold standard in measuring CCT.Measurements taken with Pentacam and Visante-OCT have demonstrated to be comparable to US.To our knowledge, this is the first study comparing central pachymetry between the 3 systems in pre- and post-LASIK eyes, and keratoconus suspects. </p><p>l * l * </p><p>l * l * </p></li><li><p>Patients and MethodsThe CCT and PCT were measured with Pentacam (Oculus Inc, Lynnwood, WA, USA) , US (Sonogage, Corneo-Gage Plus, Sonogage Inc., USA) and Visante OCT(Carl Zeiss Meditec Inc., Dublin, CA, USA,) in 163 eyes of 83 patients.3 groups were retrospectively analyzed: Keratoconus suspects, Post-LASIK and Normal patients (without Corneal pathology).Keratoconus suspects were identified by the Rabinowitz-Macdonald criteria and using the PathFinder II Corneal Analysis Software for the ATLAS Corneal Topography System (Model 9000).Influence of age and corneal thickness was evaluated in all groups, categorizing eyes with thin (500m), normal (501-550m) or thick (551m) corneas using US values. </p><p>l * l * </p><p>l * l * </p></li><li><p>Patients and MethodsData was collected at 0 mm and 6 mm from Pentacam, 0-2mm and 5-7mm from OCT, and a single value was obtained from US. Multivariate generalized estimating equations were used to analyze the correlations between the 3 measurements obtained from the patients both eyes.Mean CCT and mean PCT difference between devices were obtained for each group using multivariate linear regression.Analyzed factors included age, keratoconus suspects and previous refractive surgery (LASIK); subsequently, influence of absolute corneal thickness in pachymetry measurements was determined.</p><p> l * l * </p><p> l * l * </p></li><li><p>Results</p><p>83 patients (163 eyes) Mean age: 39 years (range 22-69 yrs.)53 female, 30 male40 eyes were keratoconus suspects, 17 post LASIK and 103 normal eyes. Mean spherical equivalent (SE) and Keratometry (Km) are shown in Table 1.Keratometry readings ranged from 36.2 D to 59.5 D.Mean CCT for each group is shown in Table 2.</p><p>l * l * </p><p>l * l * </p></li><li>ResultsCCT measurements were higher in US compared with Pentacam (6.49 1.84; p</li><li>Resultsl * l * Table 1. Spherical equivalent and Km for all the eyes and for each individual group Table 2. Mean central(CCT) and peripheral(PCT) corneal thickness with standard deviation in the 3 groups.Table 3. Mean central corneal thickness difference between Ultrasound, Pentacam and Visante OCT pachymetries in a paired analysis. Standard deviation is also shown.*P value </li><li>Resultsl * l * Table 5. US gives thicker measurements than OCT and Pentacam(p551m*500mTable 4. Peripheral corneal thickness was higher in Pentacam than in Visante OCT (constant). No influence was observed in Keratoconus or Post LASIK patients.*P value was statistically significant if </li><li><p>Resultsl * l * </p><p>l * l * </p></li><li><p>Resultsl * l * </p><p>l * l * </p></li><li><p>ConclusionThese recently new devices do not replace US pachymetry but rather complement each other in the preoperative evaluation of refractive surgery candidates, aid in the diagnosis and treatment of keratoconus suspects, help evaluate the lens, screen for glaucoma and allow room for more research in all ophthalmologic fields.Ophthalmologists should be familiar with the difference in CCT between US, Pentacam and Visante OCT.Pentacam and Visante OCT can be used interchangeably for central pachymetry, however, in post LASIK patients, Visante OCT might perform better pachymetry maps than Pentacam.Further studies are suggested in order to establish the influence of age in peripheral pachymetry. </p><p>l * l * </p><p>l * l * </p><p>*</p></li></ul>

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