Determination of corneal volume from anterior topography and topographic pachymetry: application to healthy and keratoconic eyes

Abstract

Corneal volume is a useful parameter for characterising dystrophic corneas and can aid in the detection of rare anomalies which are hardly detected with corneal topography and/or central corneal thickness evaluation. A potentially useful measure of corneal volume can be calculated from anterior corneal topography and topographic pachymetry data. Values obtained are in good agreement with previous studies using corneal tomography techniques. The methodology has been shown to have potential for retrospective analysis of data, or where no access is available to tomographical techniques.

Keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics

“…4,[6][7][8][35][36][37][38][39][40][41][42][43] In addition, new mathematic methods to reconstruct anterior corneal geometry have been developed. 44 However, it has been shown that the underlying alterations in corneal biomechanics in eyes with keratoconus induce changes in the geometry and optical properties of the anterior corneal surface 22,45 but also have an impact on the posterior corneal surface, 4,[9][10][11][12]14,15 corneal volume, 16,17 and pachymetry. 3,17 Complete characterization of the corneal structure that includes analysis of the anterior corneal surface and other objective factors is necessary for better comprehension of visual performance and symptoms in keratoconus.…”

“…1,22 Using different diagnostic technologies, with data integration in some, many studies [2][3][4][6][7][8][9]11,12,[14][15][16][17]22,24,26 have attempted to characterize the corneal morphology in eyes with keratoconus and the visual impact of the morphology. For several years, topographic analysis of the anterior corneal surface has been the main tool to characterize keratoconus.…”

“…Corneal volume was recently identified as an additional screening factor for keratoconus. [15][16][17] Posterior corneal examination and corneal volume measurement are now possible as a result of the technological advances in clinical diagnostic equipment (scanning-slit and Scheimpflug photography technologies), although these devices are not available at all ophthalmology centers. Internal astigmatism, calculated as the vectorial difference between refractive astigmatism (calculated to the corneal plane) and corneal astigmatism, 18,19 is an indirect way to determine the contribution of posterior corneal surface to ocular astigmatism, assuming a minimal contribution of the crystalline lens (clear crystalline lens).…”

A Study for Parametric Morphogeometric Operators to Assist the Detection of Keratoconus

“…These values are consistent with those published by different studies [38,39] which have reported that, in irregular corneal areas, the geometry of posterior corneal surfaces were affected due to the lower number of stromal lamellae and the smaller lamellar interconnection. In other studies, where a similar characterisation of the corneas has been described for the differentiation of pathologic eyes, the variables related to corneal thickness and volume, among others, are directly given by the software of the topographers [40,41]. However, in the present study, the morphogeometric variables are calculated from a 3D model generated using only real and non-interpolated raw point cloud data provided by the tomographer.…”

Characterization of corneal structure in keratoconus

“…24,46,74,80,81 Significant differences in corneal volume have been reported between normal and moderate keratoconic eyes (Pentacam system: 60.83 G 3.27 mm 3 controls versus 57.98 G 2.65 mm 3 moderate keratoconus), 46 suggesting the potential role for corneal volume as a diagnostic factor for corneal ectatic disorders. However, there is not enough scientific evidence of the potential usefulness of corneal volume as a screening factor for keratoconus suspect.…”