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Anterior segment OCT
Published in Pablo Artal, Handbook of Visual Optics, 2017
Corneal topography can be revealed by mapping the corneal thickness (pachymetry), surface elevation, or curvature/power mapping (keratometry) and plays an important role in the assessment of keratorefractive surgical procedures, corneal transplantation, or screening the corneal degenerations and dystrophies (e.g., keratoconus). There are several techniques enabling topographic description of the eye (Mejia-Barbosa and Malacara-Hernandez, 2001, Pinero, 2015). Access to volumetric data sets enables mapping the corneal thickness (corneal pachymetry). Several studies have been performed to show reproducibility of OCT pachymetry and agreement with standard instruments (Wirbelauer et al., 2002, Li et al., 2006, 2008, 2010, Pinero et al., 2008). The comparison of corneal pachymetry for normal subject and patient with keratoconus is presented in Figure 4.18 (Karnowski et al., 2011). The maps were calculated from corresponding 3-D data sets after segmentation of corneal interfaces and correction for light refraction.
Measuring mental workload: ocular astigmatism aberration as a novel objective index
Published in Ergonomics, 2018
Raimundo Jiménez, David Cárdenas, Rosario González-Anera, José R. Jiménez, Jesús Vera
Wavefront aberrations were measured before mentally demanding tasks, just after 11 min of mental effort, after finishing the 33 min of the mental task, and after 10 min of passive recovery. Aberrometry was performed under mesopic conditions without any cycloplegia or mydriasis by the OPD Scan III (Nidek Inc., Tokyo, Japan). The OPD-Scan lll is a five-in-one true refractive work station combined with a topographer, wavefront aberrometer, keratometer, and pupillometer, for which the repeatability and accuracy have been determined in previous studies (Burakgazi et al. 2006). Combined wavefront aberrometry and corneal topography can differentiate between aberrations caused by the anterior cornea or by the internal ocular system. Total ocular aberrations are the result of corneal and internal ocular aberrations.
Repeatability and reproducibility of the galilei G6 and its agreement with the pentacam® AXL in optical biometry and corneal tomography
Published in Expert Review of Medical Devices, 2022
Majid Moshirfar, Stephen Tenney, Shannon McCabe, Gregor Schmid
Corneal topography is a noninvasive method of measuring the morphology of the cornea [1]. It dates back to the 17th century [2,3] and made significant advances with the invention of Placido’s disc in 1880 [4]. Placido’s disc topography involves projecting concentric rings of light onto the cornea and measuring their reflection, which gives a map of corneal steepness and therefore corneal curvature, which has significant clinical utilities [5].