Assessment of an elastic model in the pathogenesis of keratoconus

Abstract

One eye of 27 patients with keratoconus and 37 normals were examined by photokeratoscopy and topographic pachometry to obtain comparative informations about the corneal shape and thickness profile, characterized by radius of the central curvature K, the coefficient of radius variation RV, the central corneal thickness T and the coefficient of thickness variation TV. RV and TV express the corneal central-peripheral variation in radius of curvature and thickness, respectively. Compared with normals the keratoconic corneas demonstrate a decrease in K and T and an increase in RV and TV. In the keratoconic eyes the decrease in K is positively correlated to the decrease in T. Further the decrease in K and T are both negatively correlated to the increase in RV and TV. Finally the increase in RV is positively correlated to the increase in TV. The results are in good accordance with an elastic model which implies increased distensibility of the keratoconic corneal tissue as a pathogenetic factor in the development of keratoconus.

Evaluation of corneal hysteresis and corneal resistance factor after corneal cross-linking for keratoconus

“…Preliminary analyses were performed to ensure no violation of the assumptions of normality, linearity and homoscedasticity. Figures 3,4,5,6,7,8 show the relationships between corneal parameters (CCT, Km and Astig.) and ORA parameters (CH and CRF) in normal and keratoconic eyes before treatment.…”

“…A significant limitation of these studies was that most of them were performed in vitro. Edmund et al [8] compared the viscoelasticity of keratoconic and normal eyes, and found that the distensibility of eyes was higher in normal eyes, so they concluded that distensibility may be an important factor in the pathogenesis of keratoconus. The same research group reported [14] that corneal rigidity tends to be lower in keratoconus, and concluded that a decrease in the corneal matrix and in the corneal tissue mass might be an important pathogenic factor in the development of keratoconus.…”

“…Previously, various investigators attempted to measure the ocular rigidity of the keratoconic eyes in order to reveal the pathologic processes that affect the corneal tissue [8,[13][14][15]. A significant limitation of these studies was that most of them were performed in vitro.…”

“…In the majority of cases, there is progressive deterioration of the visual acuity due to irregular astigmatism and corneal scarring. Keratoconic eyes also have altered corneal biomechanics [8]. According to international bibliography, they seem to be more elastic and less rigid than normal eyes.…”

Keratoconus - a Review from a Tertiary Eye-Care Center

“…Corneal transplantation is the best and most successful surgical option for advanced keratoconus, a stage where management with all other modalities fails. 6 Although the ectatic area of the cornea is generally displaced inferiorly, [7][8][9] the corneal irregularities lead to vision problems even in the early stages of the condition. Contact lens intolerance, decreased vision and/or central corneal scarring accounts for 10-25% of those keratoconus patients undergoing penetrating keratoplasty.…”