An indirect method to compare the reference centres for corneal measurements

Xu, Jin; Bao, Jinhua; Liu, Fan; He, Julian

doi:10.1111/j.1475-1313.2011.00880.x

Cited by 5 publications

(1 citation statement)

References 24 publications

(37 reference statements)

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“…7). The apex in Pentacam topography maps, defined as the point at which the mathematical gradient reduces to zero, coincides with corneal vertex where the instrument axis intersects the cornea [22]. In this study corneal vertex (or apex), which has been found earlier to be nasally displaced [23], has been similarly located on the nasal side of the geometric center of the cornea as illustrated in Fig.…”

Section: Discussionmentioning

confidence: 80%

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: Discussionmentioning

confidence: 80%