Corneal biomechanical outcome of collagen cross-linking in keratoconic patients evaluated by Corvis ST

Abstract

Purpose: A 6-month evaluation of the topographic and biomechanical changes induced by corneal collagen cross-linking (CXL) in keratoconic eyes using Pentacam and Corvis ST. Design: Longitudinal prospective case series. Methods: In this study, 67 eyes of 67 patients with progressive keratoconus (KCN) treated with “Epithelium-off” CXL were evaluated. Patients with stages 1 or 2 of KCN and a corneal thickness of at least 400 μm at the thinnest point were included. Standard ophthalmologic examinations were carried out for all patients. The topographic and biomechanical measurements of the cornea were obtained by Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) preoperatively and 6-month postoperatively. Results: The mean age of the participants was 21.68 ± 4.23 years. There was significant difference in mean spherical equivalent (SE) before and 6 months after CXL. Uncorrected and best corrected visual acuity improved postoperatively, although not statistically significant. The mean and maximum keratometry showed a significant decrease 6 months after CXL (0.93 ± 0.38 D and 1.43 ± 0.62 D, respectively p < 0.001). Among Corvis ST parameters, first applanation length and velocity (AL1 and AV1) showed statistically significant changes. The radius at highest concavity changed significantly (0.13 ± 0.37 mm mean increase after CXL; p < 0.001). A significant increase was observed in stiffness parameter A1 (SP-A1; p < 0.001) and significant decreases were noted in integrated radius (IR) and deformation amplitude ratio (DAR; p < 0.001). Conclusion: Analyzing biomechanical changes after corneal cross-linking can provide basis for efficient KCN treatment. Corvis ST parameters demonstrated changes in corneal biomechanical characteristics indicative of stiffing after CXL.

Influence of dextran solution and corneal collagen crosslinking on Corneal Biomechanical Parameters Evaluated by Corvis ST

“…Clinical results showed that SP-A1 increased significantly 6 months after CXL [22], and no significant changes was found 4 years after CXL [23]. In this study, SP-A1 was increased immediately after CXL, which was in agreement with the reported increase of corneal elastic properties from a short-term evaluation in vivo after CXL.…”

Evaluation of Dynamic Corneal Response Parameters and the Biomechanical E-Staging After Accelerated Corneal Cross-Linking in Keratoconus

“…One study compared different CXL treatment protocols and found a significant increase of SP-A1 in 21 patients who underwent accelerated CXL (9 mW/cm 2 , as in this study) 16. This finding was also observed in another study that assessed 67 corneas with mild KC 6 months after CXL 12. A third study, however, did not find a change of SP-A1 in 18 patients that were followed-up for up to 4 years after CXL according to the Dresden protocol 13.…”

Corneal Biomechanics and Intraocular Pressure Following Scleral Lens Wear in Penetrating Keratoplasty and Keratoconus

“…Strengths of the current study include the analysis of keratoconic and postkeratoplasty eyes, which has previously not been conducted after nonfenestrated scleral lens wear, and the use of the CORVIS ST instrument, which seems to be able to consistently detect changes in corneal biomechanical properties compared with other instruments (e.g., after corneal collagen cross-linking). 24,36,37 Limitations of the current study include the relatively short duration of lens wear (8 hr) in comparison to typical scleral lens wearing times (e.g., 12 hr or more per day, on a full time basis) 38 and the relatively small sample of postpenetrating keratoplasty eyes. Future studies using newer metrics to quantify corneal biomechanics may reveal new insights into potential scleral lens-induced corneal changes; 23,39–41 however, it should be noted that currently there is no method available to assess corneal biomechanics or IOP during scleral lens wear, which may differ to measurements obtained after lens removal.…”