Comparison of Visual, Tomographic, and Biomechanical Outcomes of 360 Degrees Intracorneal Ring Implantation With and Without Corneal Crosslinking for Progressive Keratoconus: A 5-Year Follow-up.

PURPOSE: To evaluate the long-term (5 years) results of 360 degrees intracorneal ring (ICR) implantation with and without corneal crosslinking (CXL) in patients with progressive keratoconus (KCN). METHOD: This historical cohort study was performed on 35 eyes with progressive KCN, which was randomly divided into 2 groups. Fourteen patients were implanted only with ICR, and 21 patients with KCN were treated with ICR plus CXL simultaneously. Uncorrected distance visual acuity (UCDVA), corrected distance visual acuity (CDVA), and refractive components were collected from patients' medical records. The biomechanical properties of patients were measured using the Corvis ST (Oculus, Inc, Weltzar, Germany). Corneal topography and aberrometry parameters were also recorded from the Pentacam HR device (Oculus). RESULTS: Both UCVA and CDVA increased in both groups after ICR implantation; however, this improvement was more significant in the ICR plus CXL group (P = 0.002 and P = 0.001, respectively). The mean improvement of CDVA in patients with ICR implantation with and without CXL was 0.56 ± 0.67 and 0.33 ± 0.61, respectively. A comparison of the long-term postoperative Tomographic and Biomechanical Index between 2 groups showed a better result in the ICR plus CXL group (P = 0.012). Topographic findings of the anterior corneal surface (flat-K, steep-K, mean-K, and astigmatism) after surgery were significantly better than before surgery in both groups (P < 0.05). CONCLUSIONS: Although ICR implantation alone might halt the KCN progression with acceptable visual, topographic, and biomechanical outcomes, the combination of ICR and CXL has an adjuvant and synergistic effect, especially in long-term follow-up.

Eye Rubbing and Transient Corneal Ectasia Detected by Topography in a Pediatric Patient.

ABSTRACT: We report on a 13-year-old girl undergoing changes in the refraction of her OS associated with eye rubbing. Corneal topography showed a corneal deformation in OS, classified as stage 1 keratoconus according to the Krumeich classification. A significant reduction in eye rubbing led to a normal corneal shape at the 1-year follow-up. Transient and fully reversible corneal ectasia can be caused by eye rubbing in pediatric age. This may have implications when counseling very young patients with eye rubbing.

Comparison of eye-rubbing effect in keratoconic eyes and healthy eyes using Scheimpflug analysis and a dynamic bidirectional applanation device.

PURPOSE: To compare the effect of eye rubbing on Scheimpflug imaging parameters and corneal biomechanics in eyes with keratoconus and healthy eyes. SETTING: Oftalmosalud Instituto de Ojos, Lima, Peru. DESIGN: Prospective cohort study. METHODS: The study included healthy and keratoconus patients who attended the institution between January 2017 and July 2017. Eye rubbing was performed for 1 minute followed by a 5-second break, followed by further rubbing for 1 minute. Baseline tests were performed before rubbing; post-rubbing tests were performed immediately after (0 minutes), and then again at 7 minutes and 14 minutes. Parameters related to anterior and posterior curvature and elevation, pachymetry, and corneal biomechanics obtained from tomography with a rotating Scheimpflug camera (Pentacam HR) and a dynamic bidirectional applanation device (Ocular Response Analyzer) were measured and compared between healthy and keratoconic eyes. RESULTS: The study included 30 healthy eyes and 31 keratoconic eyes. In the healthy group, the immediate mean changes in steeper anterior keratometry, posterior astigmatism, anterior chamber volume (ACV), flattest posterior keratometry, and Goldmann-correlated intraocular pressure (IOPg) after eye rubbing were 0.07 diopters (D) ± 0.15 (SD), -0.01 ± 0.08 D, 0.03 ± 7.06 mm3, -0.001 ± 0.04 mm, and -1.21 ± 1.99 mm Hg, respectively, whereas the mean changes in the keratoconus group were -0.03 ± 0.32 D, 0.14 ± 0.50 D, -5.09 ± 8.45 mm3, 0.03 ± 0.06 mm, and -1.61 ± 1.41 mm Hg, respectively. There were statistically significant differences between the preoperative and postoperative eye-rubbing values of posterior astigmatism, ACV, and IOPg in the keratoconus group (P = .03, P = .0003, and P = .001, respectively) but not in the healthy group (P = .65, P = .85, and P = .23, respectively). CONCLUSIONS: Unlike the healthy eyes group, the keratoconus group experienced significant changes in ACV, IOP, and corneal posterior astigmatism after eye rubbing.

Superior outcome of corneal collagen cross-linking using riboflavin with methylcellulose than riboflavin with dextran as the main supplement.

PURPOSE: To compare the effect of corneal collagen cross-linking (CXL) on progressive keratoconus using 0.1% riboflavin with either dextran or methylcellulose as the main supplement. METHODS: In a comparative case series, CXL was performed in 40 patients (40 eyes) using a riboflavin solution containing either dextran (dextran-riboflavin; n = 20) or methylcellulose (methylcellulose-riboflavin; n = 20). Changes in central corneal thickness (CCT), Scheimpflug tomography, maximal keratometry reading (Kmax ), visual acuity (VA) and endothelial cell density (ECD) were recorded. Stromal changes one month after surgery were analysed using optical coherence tomography (OCT) and in vivo confocal microscopy (IVCM). RESULTS: The CCT was significantly higher in the methylcellulose-riboflavin group during the CXL procedure. The IVCM demarcation line depth was 274 ± 80 (SD) µm in the dextran-riboflavin group and 442 ± 80 µm in the methylcellulose-riboflavin group (p < 0.001). Complete absence of keratocytes in the pre-endothelial stroma was found in none of the corneas treated with dextran-riboflavin and in 42% of the corneas treated with methylcellulose-riboflavin. Visibility of the OCT demarcation line was significantly lower in the methylcellulose-riboflavin group. Kmax and corrected distance visual acuity were improved in the methylcellulose-riboflavin group and stable in the dextran-riboflavin group after 2 years. Endothelial cell density (ECD) was stable in both groups. CONCLUSION: We found deeper structural changes in the methylcellulose-riboflavin group than in the dextran-riboflavin group. This may be explained by different riboflavin solution properties and raises safety concerns. The study also indicates improved effect using methylcellulose-riboflavin than dextran-riboflavin, possibly explained by deeper stromal CXL effect.

Corneal Biomechanical Response Following Collagen Cross-Linking With Rose Bengal-Green Light and Riboflavin-UVA.

PURPOSE: To compare the biomechanical corneal response of two different corneal cross-linking (CXL) treatments, rose bengal-green light (RGX) and riboflavin-UVA (UVX), using noninvasive imaging. METHODS: A total of 12 enucleated rabbit eyes were treated with RGX and 12 with UVX. Corneal dynamic deformation to an air puff was measured by high speed Scheimpflug imaging (Corvis ST) before and after treatment. The spatial and temporal deformation profiles were evaluated at constant intraocular pressure of 15 mm Hg, and several deformation parameters were estimated. The deformation profiles were modeled numerically using finite element analysis, and the hyperelastic corneal material parameters were obtained by inverse modeling technique. RESULTS: The corneal deformation amplitude decreased significantly after both CXL methods. The material parameters obtained from inverse modeling were consistent with corneal stiffening after both RGX and UVX. Within the treated corneal volume, we found that the elasticity decreased by a factor of 11 after RGX and by a factor of 6.25 after UVX. CONCLUSIONS: The deformation of UVX-treated corneas was smaller than the RGX-treated corneas. However, the reconstructed corneal mechanical parameters reveal that RGX produced in fact larger stiffening of the treated region (100-µm depth) than UVX (137-µm depth). Rose bengal-green light stiffens the cornea effectively, with shorter treatment times and shallower treated areas. Dynamic air puff deformation imaging coupled with mechanical simulations is a useful tool to characterize corneal biomechanical properties, assess different treatments, and possibly help optimize the treatment protocols.

Ocular allergy and keratoconus.

Keratoconus is the most common corneal ectatic disorder, the cause of which is largely unknown. Many factors have been implicated, and the ocular allergy is being one of them. The commonly proposed pathogenesis includes the release of inflammatory mediators due to eye rubbing which may alter the corneal collagen and lead to corneal ectasias. The onset of keratoconus is often early in cases associated with allergy and routine corneal topography may detect subtle forms of keratoconus. These cases may require early keratoplasty and are at an increased risk of having acute corneal hydrops. Surgical outcomes are similar to primary keratoconus cases. However, post-operative epithelial breakdown may be a problem in these cases. Control of allergy and eye rubbing is the best measure to prevent corneal ectasias in cases of ocular allergy.

New clinical pathways for keratoconus.

Pre-2000, the clinical management of keratoconus centred on rigid contact lens fitting when spectacle corrected acuity was no longer adequate, and transplantation where contact lens wear failed. Over the last decade, outcome data have accumulated for new interventions including corneal collagen crosslinking, intracorneal ring implantation, topographic phototherapeutic keratectomy, and phakic intraocular lens implantation. We review the current evidence base for these interventions and their place in new management pathways for keratoconus under two key headings: corneal shape stabilisation and visual rehabilitation.

Big-bubble deep anterior lamellar keratoplasty assisted by femtosecond laser in children.

To report the early results of big-bubble deep anterior lamellar keratoplasty assisted by femtosecond laser in children. Five eyes of 5 pediatric patients were enrolled in the study; 3 had keratoconus and 2 corneal opacities. An IntraLase 60 KHz femtosecond laser (Abbott Medical Optics, Inc) was used to create mushroom incisions on both donor and recipient corneas. All patients were evaluated for best-corrected visual acuity, spherical equivalent, refractive astigmatism, keratometric astigmatism, mean K value, and corneal thinnest point. The big bubble was always achieved, and all eyes were treated successfully without intraoperative complications. The follow-up was of 10 months. At 10 months (at least 3 months after complete suture removal), the mean postoperative best-corrected visual acuity was 20/30 (range, 20/25 to 20/30), mean spherical equivalent was -1.8 ± 1.2 diopters (D) (range, -0.25 to 1.25 D), mean refractive astigmatism was 1.8 ± 1.4 D (range, 0 to 4.0 D), mean keratometric astigmatism was 5.1 ± 2.1 D (range, 3.5 to 8.59 D), mean K value was 46.2 ± 0.8D, and mean corneal thinnest point was 581 ± 46 µm (range, 511-638 µm). Our early findings suggest that the big-bubble technique in deep anterior lamellar keratoplasty assisted by femtosecond laser is safe and effective also in pediatric patients in the attempt to decrease the rejection percentage, improve the refractive outcome, and then provide an antiamblyopic effect.

Mechanisms of rubbing-related corneal trauma in keratoconus.

PURPOSE: Corneal scarring in keratoconus, which is observed prior to contact lens wear and in association with a chronic habit of abnormal rubbing, suggests a keratocyte change to a repair phenotype in response to rubbing trauma. METHODS: This review examines known and putative mechanisms for rubbing-related corneal trauma and cone formation. RESULTS: Responses to eye rubbing (and possible causal links) may include increased corneal temperature, epithelial thinning, increased concentrations of inflammatory mediators in the precorneal tears, abnormal enzyme activity, large intraocular pressure spikes, high hydrostatic tissue pressure, thixotropically reduced ground substance viscosity, temporary displacement of ground substance from the corneal apex, buckling and flexure of fibrils associated with waves of corneal indentation, biomechanically coupled curvature transfer to the cone apex, slippage between collagen fibrils at the cone apex, and changes to keratocytes due to mechanical trauma and/or high hydrostatic pressure, in addition to scar formation. Cone formation appears to depend on a loss of shear strength and may be a consequence of a reduction in ground substance viscosity and glue function, which could allow the cornea to bend and yield to intraocular pressure. CONCLUSIONS: For some forms of keratoconus, a reduction in shear strength and cone-forming deformation may be responses to rubbing trauma. Some of the mechanisms for corneal rubbing trauma may be relevant to post-laser-assisted in situ keratomileusis ectasia or complications following other types of corneal surgery. There appear to be indications for the control of chronic habits of abnormal rubbing.