Corneal elevation indices in normal and keratoconic eyes

Abstract

Anterior corneal elevation parameters are clinically relevant measures for detecting keratoconus and suspected keratoconus eyes.

Eficacia del Orbscan II y Pentacam en la evaluación de los mapas de elevación en candidatos a cirugía refractiva mediante un análisis de repetibilidad

“…With the Orbscan II we found a mean radius of the anterior and posterior BFS and a mean radius at the point of anterior and posterior maximum elevation (table 1) similar to those found by Fam, et al in normal patients (13). However, we found a mean radius at the point of anterior and posterior maximum elevation with the Orbscan II and Pentacam different from those found by Hashemi,et al (14).…”

Characterization of corneal structure in keratoconus

“…16 De Sanctis et al 14 They obtained a mean value for this ratio of 1.874 G 0.532 in a sample of 43 keratoconus patients and of 1.103 G 0.462 in a sample of 23 keratoconus suspects using scanning-slit technology. 65 In addition, they found excellent keratoconus detection ability of the same ratio obtained using the anterior elevation data (cutoff: 0.5122, sensitivity: 99%, specificity: 95.2%). 65 Another 66 However, this dioptric value for the posterior corneal surface is not a real estimation because it is calculated assuming a change in refractive index at the posterior surface identical to that occurring at the anterior surface.…”

“…65 In addition, they found excellent keratoconus detection ability of the same ratio obtained using the anterior elevation data (cutoff: 0.5122, sensitivity: 99%, specificity: 95.2%). 65 Another 66 However, this dioptric value for the posterior corneal surface is not a real estimation because it is calculated assuming a change in refractive index at the posterior surface identical to that occurring at the anterior surface. Indeed, the posterior corneal curvature is always negative due to the refractive index change at this surface.…”

Anterior Segment Characteristics of Keratoconus Eyes Using Scheimpflug-Placido Topography

“…Detecting moderate and advanced keratoconus is not difficult using corneal topography and biomicroscopic, retinoscopic, and pachymetric findings [3]. Several indices have been proposed to help in the diagnosis of keratoconus and subclinical keratoconus with different topography systems [5][6][7][8][9][10][11][12][13]. They include quantitative descriptors such as the KISA% index proposed by Rabinowitz and Rasheed [8], the Keratoconus Prediction Index and Keratoconus Index proposed by Maeda et al [14].…”

“…Other detection schemes based on Zernike decomposition of the anterior corneal surface have been described by Schwiegerling et al [15], and Langenbucher et al [16]. With the Scheimpflug imaging system, corneal elevation either anterior or posterior started to be more investigated and researches debated which of the corneal surfaces had higher sensitivity in detecting keratoconus [11,[17][18][19][20]. Incorporating corneal thickness, corneal volume and corneal curvature using a Scheimpflug camera have been evaluated in several other articles [21,22].…”