Intracorneal Stromal Ring Can Affect the Biomechanics of Ectatic Cornea

Abstract

Purpose. The biomechanical properties of ecstatic cornea undergo changes. This study evaluates the biomechanical changes of ecstatic cornea after implantation of two types of intracorneal stromal ring (ICR). Methods. For doing this prospective cross-sectional study, 32 patients with keratoconus (KCN) were randomly divided into two 16-member groups (group I: MyoRing, group II: KeraRing). The main inclusion criteria were transparent cornea with no scar in the central part, corneal thickness >450 µ in the incision region, keratometry within 48–52 diopters, and progressive course of corneal thinning. Biomechanics of the cornea was evaluated by “ORA” and “Corvis” devices. All of the data were recorded and analyzed before implantation of the rings and 6 months thereafter. Results. The mean ages of patients of groups I and II were 26 ± 6.55 and 33.86 ± 8.5, respectively. The postoperative change of sphere refraction was significant in both groups. However, reduction in the astigmatism was significant only in group I. In addition, the change of flat meridian keratometry (Kf) was significant before and after ring implantation in group I, unlike group II. The changes in CH and CRF parameters (ORA) were not significant in either group before and after the operation. Besides, only HRC parameter (Corvis) decreased significantly in both groups before and after the operation. Conclusion. Both MyoRing and KeraRings have positive effects on the biomechanics of cornea at least during the first year after implantation. Comparison of these two types of ICR did not show significant differences in Corvis and ORA parameters.

Clinical Outcomes of Combined Simultaneous Femtosecond Kerarings Implantation and Corneal Collagen Cross-Linking in Advanced Keratoconus

“…Our results were similar to the study done by 54.38±1.17 to 47.39±0.62D [13]. has some stabilizing influence upon corneal bio-mechanics, while this impacts continue only about 6-mths, and its role is mostly for correcting the refraction and progress vision [14], which isn't sufficient to stop the development of KC, which needs CXL, that hardens the then weak and flaccid corneal stroma [15]. Managements of progressive corneal ectasia is challenging for any corneal surgeon.…”

Effects of intracorneal ring segments on the biomechanical response of the ectatic cornea to air-puff: A patient-specific numerical analysis

“…It can be explained that, regarding the inter corneal layer adhesion with the tunnel incision method in contrast to pocket cut, the cornea was less affected by the external loading and, consequently, demonstrated higher stiffness against the air-puff by exhibiting less apical displacement and a flatter central surface (greater HCR). In this context, a clinical research [36] of MyoRing and KeraRings effects on corneal biomechanics in the first year after ICRS implantation also confirms the present numerical findings. The clinical study suggested that the effect of lamellar cut in redistributing the collagen lamellae arrangement in the cornea leads to a significant difference in the highest radius of curvature and corneal flattening result, where the HCR factor can be used to assess the progression of corneal ectasia after ring implantation.…”

Continuous Intracorneal Ring Implantation in Keratoconus: Efficacy, Predictive Factors, and Complications

“…Biomechanical considerations ascribing higher stabilization of the corneal by continuous rather than interrupted segments favor ICCR implantation. 10 , 11 This is particularly relevant since some publications report of regression to baseline of CDVA improvements 12 months after ICRS implantation, particularly in progressive KC. 12 , 26 , 28–31 …”

“…All steps have been described in previous publications. 11,13 Main Outcome Measures Our primary outcome measures were the improvement of uncorrected distance visual acuity (UDVA) and CDVA as measured in logMAR chart lines. UDVA and best spectacle-CDVA were measured using a decimal scale and transformed into logMAR values for statistical analysis.…”

“…Intracorneal ring segments (ICRS) and 360° intracorneal continuous rings (ICCR) have been developed by different manufacturers and have shown their efficacy in significantly improving visual acuity in eyes with KC and in postponing or completely eliminating the need for keratoplasty. [7][8][9] The reported advantages of ICCR compared to ICRS are the more robust improvement of spherical aberrations, 7 increased biomechanical stability 10,11 and their sustained effectiveness in progressive KC. 8,[12][13][14][15] However, a recent systematic review and meta-analysis on ICCR implantation in KC highlighted the need for highpowered studies, mainly due to heterogeneity in corrected distance visual acuity (CDVA) outcome.…”