Dynamic Scheimpflug-based Assessment of Keratoconus and the Effects of Corneal Cross-linking

Abstract

Although the corneal deformation characteristics differed between groups of keratoconic and normal eyes, this study showed that the standard parameters of the Corvis ST cannot readily be used for diagnosis of keratoconus in the individual patient or to document the effect of CXL in vivo.

Influence of Pachymetry and Intraocular Pressure on Dynamic Corneal Response Parameters in Healthy Patients

“…[13][14][15] The Corvis ST (Oculus Optikgeräte GmbH; Wetzlar, Germany) was later introduced as a noncontact tonometer, which monitors the response of the cornea to an air pressure pulse using an ultra-highspeed Scheimpflug camera, and uses the captured image sequence to produce estimates of IOP and deformation response parameters. 16 Several articles have recently been published on the possible applications of the Corvis ST, particularly evaluating possible biomechanical differences in the cornea after undergoing refractive surgery procedures, [17][18][19][20][21][22] between normal and keratoconic patients, [23][24][25][26] after cross-linking, 27 and in patients with glaucoma. [28][29][30][31] However, it has been demonstrated that IOP and pachymetry have important influences on most corneal biomechanical metrics provided by both the Corvis ST and ORA.…”

Observation of sound-induced corneal vibrational modes by optical coherence tomography

“…Corneal hysteresis has shown to be reduced in ectatic disease, but its sensitivity and specificity have been insufficient to differentiate normal eyes from low-grade keratoconus [6]. Air-puff can be combined with Scheimpflug camera [7] or optical coherence tomography (OCT) [8] for image-based analysis and estimates of corneal viscoelastic parameters [9]. Other emerging techniques for measuring elastic modulus with spatial resolution include supersonic shear imaging [10], optical coherence elastography [11][12][13][14][15][16], and Brillouin microscopy [17].…”

Applanation optical coherence elastography: noncontact measurement of intraocular pressure, corneal biomechanical properties, and corneal geometry with a single instrument

“…5,7 Thus, providing an accurate measurement of corneal mechanical parameters (e.g., Young's modulus) is not straightforward, let alone based on applanation measurements. Nevertheless, commercially available noncontact tonometers (e.g., the ocular response analyzer and CorVis ST) can distinguish between healthy and keratoconic corneas, 8 but there have been conflicting results on their ability to detect corneal biomechanical changes due to therapeutic interventions such as corneal collagen crosslinking. 8,9 Therefore, it may not be entirely possible to separate the effects of corneal geometry, IOP, and corneal biomechanical properties from their respective individual measurements for corrections.…”

“…Nevertheless, commercially available noncontact tonometers (e.g., the ocular response analyzer and CorVis ST) can distinguish between healthy and keratoconic corneas, 8 but there have been conflicting results on their ability to detect corneal biomechanical changes due to therapeutic interventions such as corneal collagen crosslinking. 8,9 Therefore, it may not be entirely possible to separate the effects of corneal geometry, IOP, and corneal biomechanical properties from their respective individual measurements for corrections. Rather, a device that can accurately measure these parameters would overcome this limitation.…”