الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 132 |  |  |
| | | from | 132 | | |
Abstract
Corneal topography and thickness are important in diagnosing and evaluating progression of corneal ectatic disorders. In addition, these parameters are vital when screening candidates for refractive surgery and identifying postoperative problems.
Newer technologies, such as Scheimpflug tomography, allow additional evaluation of the posterior corneal surface, thus enabling direct evaluation of elevation and thickness changes throughout the cornea. The Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) uses a rotating Scheimpflug camera to image the anterior segment of the eye. It provides, in a single scan, anterior segment imaging (two- and three-dimensional), anterior and posterior corneal topography, complete corneal pachymetry.
Also central corneal thickness and anterior chamber depth measurements were validated and the measurements were found comparable with other imaging modalities. The Sirius topography system (SCHWIND eye. Tech. solutions GMPH main park strasse. Kleino stheim. Germany) combines two mechanisms of action, the Scheimpflug rotating camera with Placido disc topography. So, the aim of the study was to compare the anterior segment measurements provided by Scheimpflug tomography (Pentacam –HR) and Scheimpflug combined with placido disc corneal topography (Sirius).
Patients were recruited from the Ophthalmic Outpatient Clinic and a private eye center in Shebeen Elkom at Menoufia University Hospital, in Egypt and they were asked to participate in a cross-sectional study. The study was conducted between June 2022 to July 2023.
Summary
72
Each subject gave a written informed consent for participation in the study.
The overall study populations’ number was 100 eyes (50 right and 50 left) of 50 patients coming for refractive surgery with different refractive errors. There was the advantage of having the same patient to subjectively compare & evaluate the treatment modalities between eyes. Patients included in the study were individuals aged more than 18 years going for refractive surgery, all measurements were performed in the un-dilated eyes. Patients were excluded from the study when they aged less than 18 years or younger had any ocular abnormality including dry eye, corneal scars, previous ocular surgery, and contact lens wearers within the last month before the study, pregnancy or nursing.
All included patients were subjected to history taking including Personal history as name, age, sex, occupation, address, special habits and telephone number .
Present history, past history and complain is diminution of the vision since years and their desire for undergoing a refractive surgery .
The patients were subjected to complete ocular examination including best corrected visual acuity (BCVA), refraction, slit-lamp biomicroscopy, and intraocular pressure measurement (IOP) using a Goldmann applanation tonometer and fundus examination to exclude any ocular abnormality.
The anterior eye segment was analyzed by means of a rotating Scheimpflug camera (Pentacam, Oculus Inc), and a Placido disc corneal topographer (Sirius, SCHWIND SIRIUS). All shots by both the Pentacam (device 1) and Sirius (device 2) were taken between 10 am to 3 pm with the subject awake. With each machine, four reliable scans were taken by a single- experienced examiner. For the Sirius device (SCHWIND SIRIUS) manual acquisition was used, while with the Pentacam (Oculus Inc., nd
Summary
73
Wetzlar, Germany, version 1.21r.65) automated scans were acquired. Images with quality factor ˂95% were excluded. Each device was used to collect the following data from each subject: Flat anterior surface keratometry (K1), Steep anterior surface keratometry (K2), flat posterior surface keratometry (K1- back), Steep posterior surface keratometry (K2-back), Maximum keratometry (K-max), Central corneal thickness (CCT), thinnest location thickness (TLT), Q-value of the anterior surface (Q-front), Q-value of the posterior surface (Q-back), Anterior chamber depth (ACD), Anterior chamber angle (ACA) and Corneal volume.
There was a good agreement between the Oculus and Sirius measurements for most of all parameters. The mean differences between the two devices were generally small, indicating minimal systematic bias. The limits of agreement, which represent the range within which 95% of the differences between measurements fall, are also reasonably narrow for most parameters, suggesting consistent and reliable measurements. However, there were a few exceptions where larger mean differences and wider limits of agreement were observed. For parameters such as ”k2 of cornea front,” ”K max,” and ”Astigmatism of cornea front,” the mean differences were relatively larger, indicating some degree of inconsistency between the two devices. These parameters may require consideration when comparing measurements from the Oculus and Sirius devices. Overall, the oculus and Sirius measurements generally agree well for a wide range of corneal parameters. However, it is important to be cautious when interpreting results for specific parameters that show larger mean differences or wider limits of agreement, as these may indicate potential discrepancies between the two devices.