Evaluation of bilateral minimum thickness of normal corneas based on Fourier-domain optical coherence tomography

Prakash, Gaurav; Kumar, Dhivya Ashok; Agarwal, Amar; Sarvanan, Yoga; Jacob, Soosan; Athiya, Agarwal

doi:10.1016/j.jcrs.2010.02.023

Cited by 9 publications

(10 citation statements)

References 31 publications

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“…Most recent studies on bilateral corneal symmetry concentrated on the cornea's localized features such as higher-order aberrations, astigmatism axis orientation, diameter of myopic corneas, central thickness and posterior elevation at fixation point [13], [14], [15], [16], [17], [18]. Only one study [19] assessed the bilateral symmetry of overall corneal topography using anterior surface maps of 53 participants and reported similar findings to the current study.…”

Section: Discussionsupporting

confidence: 71%

“…With reference to the cornea, bilateral symmetry was recognized in the late 19 th century when Mach noted that symmetry was more easily recognized about the vertical mid-sagittal plane than about other plane orientations [13]. More recently, a high degree of bilateral corneal symmetry has been observed in measurements of higher-order corneal aberrations [14], the relation of astigmatism axis orientation [15], diameter of myopic corneas [16] and location of thinnest corneal point along vertical midline [17], in addition to other localized features including central corneal thickness, curvature and elevation [18]. In addition to the assessment of some of these earlier observations on bilateral symmetry, this study investigates symmetry in the global shape of normal corneas with a wide range of curvature, refractive error, astigmatism and thickness values.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of the Shape Symmetry of Bilateral Normal Corneas in a Chinese Population

Bao

Chen

et al. 2013

PLoS ONE

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PurposeTo investigate the bilateral symmetry of the global corneal topography in normal corneas with a wide range of curvature, astigmatism and thickness valuesDesignCross-Sectional StudyMethodsTopography images were recorded for the anterior and posterior surfaces of 342 participants using a Pentacam. Elevation data were fitted to a general quadratic model that considered both translational and rotational displacements. Comparisons between fellow corneas of estimates of corneal shape parameters (elevation, radius in two main directions, Rx and Ry, and corresponding shape factors, Qx and Qy) and corneal position parameters (translational displacements: x0, y0 and z0, and rotational displacements: α, β and γ) were statistically analyzed.ResultsThe general quadratic model provided average RMS of fit errors with the topography data of 1.7±0.6 µm and 5.7±1.3 µm in anterior and posterior corneal surfaces. The comparisons showed highly significant bilateral correlations with the differences between fellow corneas in Rx, Ry, Qx and Qy of anterior and posterior surfaces remaining insignificantly different from zero. Bilateral differences in elevation measurements at randomly-selected points in both corneal central and peripheral areas indicated strong mirror symmetry between fellow corneas. The mean geometric center (x0, y0, z0) of both right and left corneas was located on the temporal side and inferior-temporal side of the apex in anterior and posterior topography map, respectively. Rotational displacement angle α along X axis had similar distributions in bilateral corneas, while rotation angle β along Y axis showed both eyes tilting towards the nasal side. Further, rotation angle γ along Z axis, which is related to corneal astigmatism, showed clear mirror symmetry.ConclusionsAnalysis of corneal topography demonstrated strong and statistically-significant mirror symmetry between bilateral corneas. This characteristic could help in detection of pathological abnormalities, disease diagnosis, measurement validation and surgery planning.

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Section: Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Evaluation of the Shape Symmetry of Bilateral Normal Corneas in a Chinese Population

Bao

Chen

et al. 2013

PLoS ONE

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“…Several studies have been conducted to evaluate the level of interocular corneal symmetry in the normal healthy population by analyzing a great variety of parameters provided by different commercial devices used for such purpose [8][9][10][11][12][13][14][15]32,[36][37][38][39]. Specifically, high levels of interocular symmetry have been reported in variables such as corneal curvature [9,10,12,37], central corneal thickness [9,13,37,38], anterior and posterior corneal elevation [10,12,38], corneal astigmatism [9,11,36,39], minimum corneal thickness [10,12,13], corneal aberrations [14], corneal diameter [15], corneal shape factor [37], and even some biomechanical metrics [40]. This is consistent with the results obtained in our sample, as we did not find significant differences between fellow eyes in corneal asphericity, aberrations, pachymetry, and volume.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2018

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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.

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“…Even though there are few studies measuring centroid locations in different illuminations, there is a paucity of literature on the fellow eye centroid shifts in different illuminations . This is pertinent because the right and the left eyes tend to show mirror symmetry in many parameters …”

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confidence: 99%

“…17,18 This is pertinent because the right and the left eyes tend to show mirror symmetry in many parameters. [19][20][21] Even though the post-illumination pupillary redilatation response has been well documented by visual scientists, to the best of our knowledge, there are no studies in the published literature looking at the symmetry and rate of redilatation response after a strong photic stimulus in normal eyes.…”

mentioning

confidence: 99%

Assessment of bilateral pupillary centroid characteristics at varying illuminations and post‐photopic flash response using an automated pupillometer

Prakash¹,

Srivastava²,

Suhail³

et al. 2016

Clinical and Experimental Optometry

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Evaluation of bilateral minimum thickness of normal corneas based on Fourier-domain optical coherence tomography

Abstract: No author has a financial or proprietary interest in any material or method mentioned. Additional financial disclosures are found in the footnotes.

Cited by 9 publications

References 31 publications

Evaluation of the Shape Symmetry of Bilateral Normal Corneas in a Chinese Population

Evaluation of the Shape Symmetry of Bilateral Normal Corneas in a Chinese Population

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

Assessment of bilateral pupillary centroid characteristics at varying illuminations and post‐photopic flash response using an automated pupillometer

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