Assessment of Pattern and Shape Symmetry of Bilateral Normal Corneas by Scheimpflug Technology

Abstract

Purpose: The aim of this study was to assess bilateral symmetry in normal fellow eyes by using optical and geometric morphometric parameters. Methods: All participants underwent complete biocular examinations. Scheimpflug tomography data from 66 eyes of 33 patients were registered. The interocular symmetry was based on five patterns: morphogeometric symmetry, axial symmetry at the corneal vertex, angular-spatial symmetry, direct symmetry (equal octants), and enantiomorphism (mirror octants). Results: No statistically significant differences were found between right and left eyes in corneal morphogeometric (p ≥ 0.488) and aberrometric parameters (p ≥ 0.102). Likewise, no statistically significant differences were found in any of the axial symmetry parameters analyzed (p ≥ 0.229), except in the surface rotation angle beta (p = 0.102) and translation coordinates X0 and Y0 (p < 0.001) for the anterior corneal surface, and the rotation angle gamma (p < 0.001) for the posterior surface. Similarly, no statistically significant differences were identified for direct symmetry (p ≥ 0.20) and enantiomorphism (p ≥ 0.75), except for some elevation data in the posterior surface (p < 0.01). Conclusions: The level of symmetry of both corneas of a healthy individual is high, with only some level of disparity between fellow corneas in rotation and translation references. Abnormalities in this pattern of interocular asymmetry may be useful as a diagnostic tool.

Changes in the 3D Corneal Structure and Morphogeometric Properties in Keratoconus after Corneal Collagen Crosslinking

“…Our research group developed a new method to perform a more complete morphogeometric analysis of the cornea on the basis of the data obtained from a Scheimpflug imaging-based tomography system [8]. This advanced corneal analysis has been demonstrated to be useful for characterizing the corneal structure in patients with keratoconus [9,10] for subclinical and clinical keratoconus detection [11][12][13], patient education [14], and even for characterizing the symmetry of the corneal profile between both eyes of healthy patients [15]. The aim of the current study was to conduct this 3D morphogeometric analysis to evaluate corneal changes after CXL in keratoconus patients and during a 6 month follow-up period.…”

“…A custom-made script programmed in the Matlab R2017b (Mathworks, Natick, USA) software was created to transform each point of the cloud provided by the tomographer in polar coordinates into the Cartesian format. This procedure has been meticulously described in several previous research works [8][9][10][11][12][13][14][15]. The program provides a. CSV file containing data of the points of clouds that describe both the anterior and posterior corneal surfaces for the area comprised between the geometric center of the cornea (r = 0 mm) and the mid-peripheral area (r = 4 mm).…”

“…The program provides a. CSV file containing data of the points of clouds that describe both the anterior and posterior corneal surfaces for the area comprised between the geometric center of the cornea (r = 0 mm) and the mid-peripheral area (r = 4 mm). This zone usually contains most corneal anomalies for not only diseased, but also healthy eyes [8][9][10][11][12][13][14][15]. Afterward, both surfaces were imported to the Rhinoceros V 5.0 (MCNeel and Associates, Seattle, USA) software, and the "patch" function was used to find the surfaces that better fitted the clouds of points.…”

Paediatric Orthopaedic Surgery with 3D Printing: Improvements and Cost Reduction

“…However, it is important to note that this research focused on a limited number of patients, it should be reproduced many times with a higher number of patients as shown for other methodologies in [15,16].…”

Design Specifications for an Auxiliary Incision Retractor in Dacryocystorhinostomy Surgeries

“…The ellipse plotted by Equation (11) has a workspace area A = 1.57 cm 2 , and the three circles do not have intersected areas and the value is A = 1.50 cm 2 ( Figure 6). The volumetric workspace will change at different depths [23], Figure 7 shows a 3D representation of the incision retracted at a 1 cm maximal length. The punctual strain from circles C 1 and C 3 are placed in points (±0.25, ±0.86) and the strain value is σ LR = 625,000 N/m 2 .…”