Corneal Biomechanics in Unilateral Keratoconus and Fellow Eyes with a Scheimpflug-based Tonometer

Abstract

A best predictive linear combination of corneal biomechanical variables was tested including diameter of the flattened cornea in the second applanation and central corneal thickness. This combination was considered as the best in terms of its prediction capacity, simplicity and clinical application. This formula may be useful in clinical practice to discriminate between normal eyes and incipient keratoconus.

Comprehensive evaluation of corneas from normal, forme fruste keratoconus and clinical keratoconus patients using morphological and biomechanical properties

“…Despite extensive research in this field, the exact etiology of the disease is not clear, and the current diagnostic criteria for the disease are mainly based on the combination of symptoms and signs of the disease as well as morphological evaluation of the cornea [3]. Recently, some researchers [4,5] have proposed that during the progression of keratoconus, the corneal Bowman's membrane ruptures, resulting in the disorganization of the collagen fibers and imbalance of its material composition, which further caused the corneal protein kinase and other catabolic enzyme levels to increase and the protein kinase inhibitor levels to decrease. These enzyme changes destroy the collagen structure of the cornea and reduce the corneal stroma, which leads to unstable corneal biomechanical properties and reduced corneal mechanical strength, thus causing corneal thinning and ectasia.…”

Comprehensive Evaluation of Corneas from Normal, Forme Fruste Keratoconus, and Clinical Keratoconus Patients using Morphological and Biomechanical Properties

“…Therefore, it may not be useful for patients in the early stages of keratoconus or with no apparent signs to be assessed using only traditional morphological devices. In addition, although progressive thinning of keratoconus may be caused by weakened corneal biomechanical resistance and decreased biomechanical properties 4,5 , keratoconus cannot be solely attributed to changes in corneal morphology or biomechanical properties 19,20 .…”

“…The Corvis ST (software version 1.5r1902) evaluates the dynamic corneal deformation response to an air-puff pulse. Details and principles of the Corvis ST are described elsewhere 5 . Only measurements where the ''quality speci cation'' read OK were accepted.…”

“…Recently, some researchers 4,5 have proposed that during the progression of keratoconus, the corneal Bowman's membrane ruptures, resulting in the disorganization of the collagen bers and imbalance of its material composition, which further caused the corneal protein kinase and other catabolic enzyme levels to increase, and the protein kinase inhibitor levels to decrease. These enzyme changes destroy the collagen structure of the cornea and reduce the corneal stroma, which leads to unstable corneal biomechanical properties and reduced corneal mechanical strength, thus causing corneal thinning and ectasia.…”

“…However, for Pentacam and ORA, some studies 10,11 suggested that the discriminating ability of the corneal hysteresis (CH) and corneal resistance factor (CRF) from ORA was poor, although most of the other parameters of the output of these two devices were signi cantly different between the keratoconus and normal eyes. Furthermore, although a few studies have used the above three kinds of devices for analysis, they were all studies on patients with clinical keratoconus 5,12,13 . And at most, these studies only analyzed and compared the diagnostic ability of single output parameters of the devices 5,12 .…”